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Phase Change Material Heat Exchanger Life Test
Lillibridge, Sean; Stephan, Ryan
Low Lunar Orbit (LLO) poses unique thermal challenges for the orbiting space craft, particularly regarding the performance of the radiators. The IR environment of the space craft varies drastically from the light side to the dark side of the moon. The result is a situation where a radiator sized for the maximal heat load in the most adverse situation is subject to freezing on the dark side of the orbit. One solution to this problem is to implement Phase Change Material (PCM) Heat Exchangers. PCM Heat Exchangers act as a "thermal capacitor," storing thermal energy when there is too much being produced by the space craft to reject to space, and then feeding that energy back into the thermal loop when conditions are more favorable. Because they do not use an expendable resource, such as the feed water used by sublimators and evaporators, PCM Heat Exchangers are ideal for long duration LLO missions. In order to validate the performance of PCM Heat Exchangers, a life test is being conducted on four n-Pentadecane, carbon filament heat exchangers. Fluid loop performance, repeatability, and measurement of performance degradation over 2500 melt-freeze cycles will be performed.
A Liquid-Liquid Thermoelectric Heat Exchanger as a Heat Pump for Testing Phase Change Material Heat Exchangers
Sheth, Rubik B.; Makinen, Janice; Le, Hung V.
The primary objective of the Phase Change HX payload on the International Space Station (ISS) is to test and demonstrate the viability and performance of Phase Change Material Heat Exchangers (PCM HX). The system was required to pump a working fluid through a PCM HX to promote the phase change material to freeze and thaw as expected on Orion's Multipurpose Crew Vehicle. Due to limitations on ISS's Internal Thermal Control System, a heat pump was needed on the Phase Change HX payload to help with reducing the working fluid's temperature to below 0degC (32degF). This paper will review the design and development of a TEC based liquid-liquid heat exchanger as a way to vary to fluid temperature for the freeze and thaw phase of the PCM HX. Specifically, the paper will review the design of custom coldplates and sizing for the required heat removal of the HX.
Subscale Water Based Phase Change Material Heat Exchanger Development
Sheth, Rubik; Hansen, Scott
Supplemental heat rejection devices are required in many spacecraft as the radiators are not sized to meet the full heat rejection demand. One means of obtaining additional heat rejection is through the use of phase change material heat exchangers (PCM HX's). PCM HX's utilize phase change to store energy in unfavorable thermal environments (melting) and reject the energy in favorable environments (freezing). Traditionally, wax has been used as a PCM on spacecraft. However, water is an attractive alternative because it is capable of storing about 40% more energy per unit mass due to its higher latent heat of fusion. The significant problem in using water as a PCM is its expansion while freezing, leading to structural integrity concerns when housed in an enclosed heat exchanger volume. Significant investigation and development has taken place over the past five years to understand and overcome the problems associated with water PCM HX's. This paper reports on the final efforts by Johnson Space Center's Thermal Systems Branch to develop a water based PCM HX. The test article developed and reported on is a subscale version of the full-scale water-based PCM HX's constructed by Mezzo Technologies. The subscale unit was designed by applying prior research on freeze front propagation and previous full-scale water PCM HX development. Design modifications to the subscale unit included use of urethane bladder, decreased aspect ratio, perforated protection sheet, and use of additional mid-plates. Testing of the subscale unit was successful and 150 cycles were completed without fail.
Experimental Investigation of Ice Phase Change Material Heat Exchangers
Leimkuehler, Thomas O.; Stephan, Ryan A.
Phase change materials (PCM) may be useful for spacecraft thermal control systems that involve cyclical heat loads or cyclical thermal environments. Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. This can result in a decreased turndown ratio for the radiator and a reduced system mass. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents an overview of the results of this investigation from the past three years.
Energy Technology Data Exchange (ETDEWEB)
Craig, L.B.; Farma, A.J.
This invention concerns a heat exchanger as used in a space heater, of the type in which hot exhaust gases transfer heat to water or the like flowing through a helical heat exchange coil. A significant improvement to the efficiency of the heat exchange occurring between the air and water is achieved by using a conduit for the water having external helical fluting such that the hot gases circulate along two paths, rather than only one. A preferred embodiment of such a heat exchanger includes a porous combustion element for producing radiant heat from a combustible gas, surrounded by a helical coil for effectively transferring the heat in the exhaust gas, flowing radially from the combustion element, to the water flowing through the coil. 4 figs.
Water Based Phase Change Material Heat Exchanger Development
Hansen, Scott W.; Sheth, Ribik B.; Atwell, Matt; Cheek, Ann; Agarwal, Muskan; Hong, Steven; Patel, Aashini,; Nguyen, Lisa; Posada, Luciano
In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to reject the full heat load requirement. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HXs do not use a consumable, thereby leading to reduced launch mass and volume requirements. Studies conducted in this paper investigate utilizing water's high latent heat of formation as a PCM, as opposed to traditional waxes, and corresponding complications surrounding freezing water in an enclosed volume. Work highlighted in this study is primarily visual and includes understanding ice formation, freeze front propagation, and the solidification process of water/ice. Various test coupons were constructed of copper to emulate the interstitial pin configuration (to aid in conduction) of the proposed water PCM HX design. Construction of a prototypic HX was also completed in which a flexible bladder material and interstitial pin configurations were tested. Additionally, a microgravity flight was conducted where three copper test articles were frozen continuously during microgravity and 2-g periods and individual water droplets were frozen during microgravity.
Continued Water-Based Phase Change Material Heat Exchanger Development
Hansen, Scott W.; Sheth, Rubik B.; Poynot, Joe; Giglio, Tony; Ungar, Gene K.
In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to meet the full heat rejection demands. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HX's do not use a consumable, thereby leading to reduced launch mass and volume requirements. In continued pursuit of water PCM HX development two full-scale, Orion sized water-based PCM HX's were constructed by Mezzo Technologies. These HX's were designed by applying prior research on freeze front propagation to a full-scale design. Design options considered included bladder restraint and clamping mechanisms, bladder manufacturing, tube patterns, fill/drain methods, manifold dimensions, weight optimization, and midplate designs. Two units, Units A and B, were constructed and differed only in their midplate design. Both units failed multiple times during testing. This report highlights learning outcomes from these tests and are applied to a final sub-scale PCM HX which is slated to be tested on the ISS in early 2017.
Phase Change Material (PCM) Heat Exchanger Development Project
National Aeronautics and Space Administration — Project has identified two PCM HX concepts that will be designed, developed and demonstrated on-board the International Space Station (ISS):The first heat exchanger...
International Nuclear Information System (INIS)
A heat exchanger having primary and secondary conduits in heat-exchanging relationship is described comprising: at least one serpentine tube having parallel sections connected by reverse bends, the serpentine tube constituting one of the conduits; a group of open-ended tubes disposed adjacent to the parallel sections, the open-ended tubes constituting the other of the conduits, and forming a continuous mass of contacting tubes extending between and surrounding the serpentine tube sections; and means securing the mass of tubes together to form a predetermined cross-section of the entirety of the mass of open-ended tubes and tube sections
Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann
A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.
Heat Transfer Modeling of Phase Change Materials in Multiple Plates Heat Exchanger
Directory of Open Access Journals (Sweden)
M. Alipanah
Full Text Available Nowadays, given the increasing importance of energy sources, the possibility of energy storage in the heat exchangers through the Phase Change Materials (PCM and releasing it when needed have been extremely essential. This study seeks to model the domestic water heat system in which the paraffin is as the phase change material and it stores the solar energy. The behavior of a PCM plate was studied by writing the governing equations and solving them as the one-dimensional, implicit method and through numerical calculation of the method equations. Given the confirmed accuracy of performed modeling by the results of similar studies for the complete melting and solidification of PCM, the application of this system seems appropriate for the solar domestic water heaters.
Experimental Investigation of Phase Change inside a Finned-Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
M. Rahimi
Full Text Available An experimental study is conducted in order to investigate melting and solidification processes of paraffin RT35 as phase change materials in a finned-tube. Therefore the effect of using fins in this study as well as some operational parameters is considered. The motivation of this study is to design and construct a novel storage unit and to compare it with a finless heat exchanger. A series of experiments are conducted to investigate the effect of increasing the inlet temperature and flow rate on the charging and discharging processes of the phase change material. It is shown that, using fins in phase change process enhances melting and solidification procedures. The trend of this variation is different for the heat exchangers; increasing the inlet temperature for the bare tube heat exchanger more effectively lowers melting time. Similarly, flow rate variation varies the solidification time more intensely for the bare tube heat exchanger.
The Gravitational Heat Exchanger
De Aquino, Fran
The heat exchangers are present in many sectors of the economy. They are widely used in Refrigerators, Air-conditioners, Engines, Refineries, etc. Here we show a heat exchanger that works based on the gravity control. This type of heat exchanger can be much more economic than the conventional heat exchangers.
Long-Term Changes in a Heat Exchanger Steel
International Nuclear Information System (INIS)
The steel ASTM A213 P22 is used for superheater outlet header in power plants. During duty cycles lasting over tens of years the temperature is of the order of 545 deg. C and the pressure 125 atm. The microscopic changes in these steels are hard to analyze under working conditions, but they are believed to be responsible for the appearance of creeps in such devices. Investigation of the microscopic modifications will help to predict future failures due to creeps, increasing the reliability and saving a lot of money.We report the investigation of such changes in ASTM A213 P22 steel in use for 30 years as a Superheater header at Haifa power station. The analysis has been carried out using Moessbauer Spectroscopy, X-ray diffraction and optical microscopy. As a result it seems that the morphology and phase change of the carbide phases M3C/M7C3 and M23C6 are the most prominent changes leading to the material failures.
Loukota, Martin
This bachelor thesis solves design of a heat exchanger for hot water boiler with gasification chamber for preheating the combustion air with the heat of the combustion products. Calculation values were experimentally measured. Thesis contains brief description of the shell and tube heat exchanger, stoichiometric combustion calculation, geometrical dimensions design of the heat exchanger, pressure loss and thermal performance calculation. It also includes drawings of the designed exchanger.
Testing and Failure Mechanisms of Ice Phase Change Material Heat Exchangers
Leimkuehler, Thomas O.; Stephan, Ryan A.; Hawkins-Reynolds, Ebony
Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as specific spacecraft orientations in Low Earth Orbit (LEO) and low beta angle Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM s have over evaporators in this scenario is that they do not use a consumable. The use of water as a PCM rather than the more traditional paraffin wax has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. A number of ice PCM heat exchangers were fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion were investigated. This paper presents the results of testing that occurred from March through September of 2010 and builds on testing that occurred during the previous year.
Development, Testing, and Failure Mechanisms of a Replicative Ice Phase Change Material Heat Exchanger
Leimkuehler, Thomas O.; Hansen, Scott; Stephan, Ryan A.
Phase change materials (PCM) may be useful for thermal control systems that involve cyclical heat loads or cyclical thermal environments such as Low Earth Orbit (LEO) and Low Lunar Orbit (LLO). Thermal energy can be stored in the PCM during peak heat loads or in adverse thermal environments. The stored thermal energy can then be released later during minimum heat loads or in more favorable thermal environments. One advantage that PCM's have over evaporators in this scenario is that they do not use a consumable. Wax PCM units have been baselined for the Orion thermal control system and also provide risk mitigation for the Altair Lander. However, the use of water as a PCM has the potential for significant mass reduction since the latent heat of formation of water is approximately 70% greater than that of wax. One of the potential drawbacks of using ice as a PCM is its potential to rupture its container as water expands upon freezing. In order to develop a space qualified ice PCM heat exchanger, failure mechanisms must first be understood. Therefore, a methodical experimental investigation has been undertaken to demonstrate and document specific failure mechanisms due to ice expansion in the PCM. An ice PCM heat exchanger that replicates the thermal energy storage capacity of an existing wax PCM unit was fabricated and tested. Additionally, methods for controlling void location in order to reduce the risk of damage due to ice expansion are investigated. This paper presents the results to date of this investigation. Nomenclature
Microplate Heat Exchanger Project
National Aeronautics and Space Administration — We propose a microplate heat exchanger for cryogenic cooling systems used for continuous flow distributed cooling systems, large focal plane arrays, multiple...
Barnes, George
Discusses the heat-transfer systems of different animals. Systems include heat conduction into the ground, heat transferred by convection, heat exchange in lizards, fish and polar animals, the carotid rete system, electromagnetic radiation from animals and people, and plant and animal fiber optics. (MDH)
Microscale Regenerative Heat Exchanger
Moran, Matthew E.; Stelter, Stephan; Stelter, Manfred
The device described herein is designed primarily for use as a regenerative heat exchanger in a miniature Stirling engine or Stirling-cycle heat pump. A regenerative heat exchanger (sometimes called, simply, a "regenerator" in the Stirling-engine art) is basically a thermal capacitor: Its role in the Stirling cycle is to alternately accept heat from, then deliver heat to, an oscillating flow of a working fluid between compression and expansion volumes, without introducing an excessive pressure drop. These volumes are at different temperatures, and conduction of heat between these volumes is undesirable because it reduces the energy-conversion efficiency of the Stirling cycle.
Energy Technology Data Exchange (ETDEWEB)
Lowenstein, Andrew (Princeton, NJ); Sibilia, Marc J. (Princeton, NJ); Miller, Jeffrey A. (Hopewell, NJ); Tonon, Thomas (Princeton, NJ)
A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.
Melting of Nanoprticle-Enhanced Phase Change Material inside Shell and Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
Seiyed Mohammad Javad Hosseini
Full Text Available This paper presents a numerical study of melting of Nanoprticle-Enhanced phase change material (NEPCM inside a shell and tube heat exchanger using RT50 and copper particles as base material and nanoparticle, respectively. In this study, the effects of nanoparticles dispersion (, 0.03, and 0.05 on melting time, liquid fraction, and penetration length are investigated. The results show that the melting time decreases to 14.6% and the penetration length increases to 146% with increasing volume fraction of nanoparticle up to .
Thermoelectric heat exchange element
Callas, James J.; Taher, Mahmoud A.
A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.
Mapping temperature-induced conformational changes in the Escherichia coli heat shock transcription factor sigma 32 by amide hydrogen exchange
DEFF Research Database (Denmark)
Rist, Wolfgang; Jørgensen, Thomas J D; Roepstorff, Peter;
Stress conditions such as heat shock alter the transcriptional profile in all organisms. In Escherichia coli the heat shock transcription factor, sigma 32, out-competes upon temperature up-shift the housekeeping sigma-factor, sigma 70, for binding to core RNA polymerase and initiates heat shock...... gene transcription. To investigate possible heat-induced conformational changes in sigma 32 we performed amide hydrogen (H/D) exchange experiments under optimal growth and heat shock conditions combined with mass spectrometry. We found a rapid exchange of around 220 of the 294 amide hydrogens at 37...
Heat exchanger design handbook
Thulukkanam, Kuppan
Completely revised and updated to reflect current advances in heat exchanger technology, Heat Exchanger Design Handbook, Second Edition includes enhanced figures and thermal effectiveness charts, tables, new chapter, and additional topics--all while keeping the qualities that made the first edition a centerpiece of information for practicing engineers, research, engineers, academicians, designers, and manufacturers involved in heat exchange between two or more fluids.See What's New in the Second Edition: Updated information on pressure vessel codes, manufacturer's association standards A new c
Counterflow Regolith Heat Exchanger
Zubrin, Robert; Jonscher, Peter
A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.
Heat exchanger restart evaluation
Energy Technology Data Exchange (ETDEWEB)
Morrison, J.M.; Hirst, C.W.; Lentz, T.F.
On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4kA was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized herein.
Microgravity condensing heat exchanger
Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)
A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.
Warburton, Robert E. (Inventor); Cuva, William J. (Inventor)
The present invention relates to a heat exchanger panel which has broad utility in high temperature environments. The heat exchanger panel has a first panel, a second panel, and at least one fluid containment device positioned intermediate the first and second panels. At least one of the first panel and the second panel have at least one feature on an interior surface to accommodate the at least one fluid containment device. In a preferred embodiment, each of the first and second panels is formed from a high conductivity, high temperature composite material. Also, in a preferred embodiment, the first and second panels are joined together by one or more composite fasteners.
Water Phase Change Heat Exchanger System Level Analysis for Low Lunar Orbit
Navarro, Moses; Ungar, Eugene; Sheth, Rubik; Hansen, Scott
In low Lunar orbit (LLO) the thermal environment is cyclic - extremely cold in the eclipse and as warm as room temperature near the subsolar point. Phase change material heat exchangers (PCHXs) are the best option for long term missions in these environments. The Orion spacecraft will use a n-pentadecane wax PCHX for its envisioned mission to LLO. Using water as a PCM material is attractive because its higher heat of fusion and greater density result in a lighter, more compact PCHX. To assess the use of a water PCHX for a human spacecraft in a circular LLO, a system level analysis was performed for the Orion spacecraft. Three cases were evaluated: 1) A one-to-one replacement of the wax PCHX on the internal thermal control loop with a water PCHX (including the appropriate control modifications), 2) reducing the radiator return setpoint temperature below Orion's value to enhance PCHX freezing, and 3) placing the water PCM on the external loop. The model showed that the water PCHX could not be used as a drop-in replacement for the wax PCHX. It did not freeze fully during the eclipse owing to its low freezing point. To obtain equivalent performance, 40% more radiator area than the Orion baseline was required. The study shows that, although water PCHXs are attractive at a component level, system level effects mean that they are not the best choice for LLO.
Optimization of heat exchanger for indirectly heated water heater
Kaduchová Katarína; Lenhard Richard; Jandačka Jozef
Due to the optimization of geometrical parameters of the heat exchanger in indirect heated water heaters created a mathematical model of heating hot water, by which I have subsequently made the simulation of the device to change its geometrical parameters. Based on these results, the impacts of the geometrical parameters affect the performance of the heat exchanger. The results of the optimization to create a CFD model which watched at the behavior of optimized heat exchanger for indirect hea...
International Nuclear Information System (INIS)
The invention concerns a heat exchanger of which the tubes, placed in a long casing, cross the casing cover in a sealed manner. These tubes are fixed to the tube plate forming this cover or to the branch tubes it comprises by means of compression joints. These joints make it possible to do away with welds that are sources of defects and to improve the operational safety of the apparatus. An advantageous form of the heat exchanger under the invention includes a manifold for each thermal exchange fluid, and one end of each tube is connected to this manifold by a pipe that is itself connected to the tube by a threaded connection. The latter provides for easy disconnection of the pipe in order to introduce a probe for inspecting the state of the tubes
Modelling of Multistream LNG Heat Exchangers
Soler Fossas, Joan
The main goal of this thesis is to find out if a liquefied natural gas multistream heat exchanger numerical model is achievable. This should include several features usually neglected in nowadays available heat exchanger models, such as flow maldistribution, changes in fluid properties and heat exchanger dynamic behaviour. In order to accomplish that objective a simpler case is modelled. Efforts are put in achieving numerical stability.A counter flow natural gas and mixed refrigerant heat exc...
Heat exchanger with removable orifice
International Nuclear Information System (INIS)
A nuclear reactor steam generator heat exchanger is described which has orifices in the entrance openings of the heat exchange tubes which, although securely fastened to the tubes, can be easily removed by remote handling equipment. (U.K.)
Aarnes, Sofie Marie
Reduction of the energy used to acclimatise buildings is a huge challenge simultaneously with the implementation of air tight low energy buildings. In residential buildings with several living units centralised air handling units are the most energy efficient system. However, in a centralised system there is important to avoid leakages of pollutions between the exhaust air and the supply air. This leads to that flat plate heat exchangers are used instead of the more energy efficient rotary he...
Podobeková, Veronika; Peráčková, Jana
The article discusses utilization of heat from waste water in sewage. During the year, temperature of water in sewage ranges between 10 °C and 20 °C and the heat from sewage could be used for heating, cooling and hot water preparation in building. The heat is extracted through a transfer surface area of the heat exchanger into the heat pump, which is able to utilize the low–potential energy. Different design and types of the heat exchangers in sewage are dealt with: heat exchangers embedded i...
International Nuclear Information System (INIS)
The plate exchanger described includes a series of individual modules joined together, communicating in pairs to delimit two flow circuits separated by two fluids mutually exchanging calories. Each module includes at least one flat frame around a central cavity, at least two apertures made in the frame respectively for the inlet and oulet of the fluids crossing the cavity and at least one opening in the frame for the fluids to pass to a neighbouring module. The frames of the modules form a stack plane upon plane and are isolated by a thin leak-tight sheet parallel to the plane of the frames and separating the fluid substances in two superimposed frames. The heat transfer between these fluids occurs through this thin sheet from one module to the next in the stack
Compact cryocooler heat exchangers
International Nuclear Information System (INIS)
Compact heat exchangers are subject to different constraints as a room temperature gas is cooled down by a cold stream returning from a JT valve (or a similar cryoprocess component). In particular, the optimization of exchangers for liquid helium systems has to cover a wide range in temperature and density of the fluid. In the present work we address the following thermodynamic questions: 1. The optimization of intermediate temperatures which optimize stage operation (a stage is assumed to have a constant cross section); 2. The optimum temperature difference available for best overall economic performance values. The results are viewed in the context of porous media concepts applied to rather low speeds of fluid flow in narrow passages. In this paper examples of fluid/solid constraints imposed in this non-classical low temperature area are presented
Izenson, Michael G.; Crowley, Christopher J.
A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.
Counterflow Regolith Heat Exchanger Project
National Aeronautics and Space Administration — The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat...
Cryogenic regenerative heat exchangers
Ackermann, Robert A
An in-depth survey of regenerative heat exchangers, this book chronicles the development and recent commercialization of regenerative devices for cryogenic applications. Chapters cover historical background, concepts, practical applications, design data, and numerical solutions, providing the latest information for engineers to develop advanced cryogenic machines. The discussions include insights into the operation of a regenerator; descriptions of the cyclic and fluid temperature distributions in a regenerator; data for various matrix geometries and materials, including coarse and fine bronze, stainless steel-woven wire mesh screens, and lead spheres; and unique operating features of cryocoolers that produce deviations from ideal regenerator theory.
Tu, Jianping Gene; Shih, Wei
A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C-C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements. In order to maximize thermal conductivity, the majority of carbon fiber is aligned in the fin direction resulting in 300 W/m.K or higher conductivity in the fin directions. As a result of this fiber orientation, the coefficient of thermal expansion (CTE) of the C-C composite in both non-fiber directions matches well with the CTE of various high-temperature metal alloys. This allows the joining of fins and parting sheets by using high-temperature braze alloys.
Quasi-steady-state model of a counter flow air-to-air heat exchanger with phase change
DEFF Research Database (Denmark)
Rose, Jørgen; Nielsen, Toke Rammer; Kragh, Jesper;
-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes...... European and arctic climate conditions. (C) 2007 Elsevier Ltd. All rights reserved....
International Nuclear Information System (INIS)
In a plate heat exchanger required to handle corrosive, toxic or radioactive fluids, wherein each plate has a peripheral recess or like formation adapted for receiving an elastomeric gasket, the plates are welded together in pairs by the method comprising the steps of inserting into the gasket recess of a first plate of said pair a metal packing piece and welding the second place (e.g. by a laser or electron beam weld running along the base of the recess) superimposing a second plate on to the first in contact with the packing piece and welding the second plate to the packing piece (e.g. by a laser or electron beam weld). The packing piece may be of hollow or solid cross section and is preferably of the same material (e.g. titanium or stainless steel) as the plates. In use a service fluid in heat exchange with the said corrosive etc. fluid is confined by peripheral and normally elastomeric gaskets. (author)
Heat exchangers for waste heat recovery
Energy Technology Data Exchange (ETDEWEB)
Al-Rabghi, O.M.; Akyurt, M.; Najjar, Y.S.H.; Alp, T. (King Abdulaziz Univ., Jeddah (Saudi Arabia). College of Engineering)
A survey is made of the equipment used for heat recovery and utilization. Types and merits of commonly employed heat exchangers are presented, and criteria for selecting heat exchangers are summarized. Applications for waste heat recovery are emphasized. It is concluded that careful selection and operation of such equipment would be expected to result in energy savings as well as problem-free operation. (author)
Numerical research of heat transfer in gas heat exchanger
Khomutov Eugene O.; Gil Andrey V.
The article presents a numerical study of heat and mass transfer based on the finite volume method. Researched by installing a tubular heat exchanger for heating of natural gas. The results according to changes in temperature of the natural gas depend on the initial temperature of the heating flow. The results can be used in the analysis of further effective combustion.
International Nuclear Information System (INIS)
There are two ways to rapir heater tubes in tubular heat exchangers, partial replacement of tubes and a technique called sleeving. In the former case, the defective tube section is cut out, removed, and replaced by a new section butt welded to the old piece of tube which remained in place. In the sleeving technique, a tube sleeve is slid into the defective tube and, after expansion, welded to the original tube. In this case, the welding technique employed is not laser welding, as is often maintained in the literature, but TIG pulsation welding. The results of preliminary tests and the qualification of both processes are outlined in the article; an account is given also of the replacement of the tube sections when repairing condensate coolers. (orig.)
Next Generation Microchannel Heat Exchangers
Ohadi, Michael; Dessiatoun, Serguei; Cetegen, Edvin
In Next Generation Microchannel Heat Exchangers, the authors' focus on the new generation highly efficient heat exchangers and presentation of novel data and technical expertise not available in the open literature. Next generation micro channels offer record high heat transfer coefficients with pressure drops much less than conventional micro channel heat exchangers. These inherent features promise fast penetration into many mew markets, including high heat flux cooling of electronics, waste heat recovery and energy efficiency enhancement applications, alternative energy systems, as well as applications in mass exchangers and chemical reactor systems. The combination of up to the minute research findings and technical know-how make this book very timely as the search for high performance heat and mass exchangers that can cut costs in materials consumption intensifies.
Quasi-steady-state model of a counter-flow air-to-air heat-exchanger with phase change
Energy Technology Data Exchange (ETDEWEB)
Rose, Joergen; Nielsen, Toke Rammer; Kragh, Jesper; Svendsen, Svend [Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, DK-2800 Kgs. Lyngby (Denmark)
Using mechanical ventilation with highly efficient heat-recovery in northern European or arctic climates is a very efficient way of reducing the energy use for heating in buildings. However, it also presents a series of problems concerning condensation and frost formation in the heat-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes into account the effects of condensation and frost formation. The model is developed as an Excel spreadsheet, and specific results are compared with laboratory measurements. As an example, the model is used to determine the most energy-efficient control strategy for a specific heat-exchanger under northern European and arctic climate conditions. (author)
Heat exchanger leakage problem location
Directory of Open Access Journals (Sweden)
Jícha Miroslav
Full Text Available Recent compact heat exchangers are very often assembled from numerous parts joined together to separate heat transfer fluids and to form the required heat exchanger arrangement. Therefore, the leak tightness is very important property of the compact heat exchangers. Although, the compact heat exchangers have been produced for many years, there are still technological problems associated with manufacturing of the ideal connection between the individual parts, mainly encountered with special purpose heat exchangers, e.g. gas turbine recuperators. This paper describes a procedure used to identify the leakage location inside the prime surface gas turbine recuperator. For this purpose, an analytical model of the leaky gas turbine recuperator was created to assess its performance. The results obtained are compared with the experimental data which were acquired during the recuperator thermal performance analysis. The differences between these two data sets are used to indicate possible leakage areas.
Heat exchanger leakage problem location
Hejčík, Jiří; Jícha, Miroslav
Recent compact heat exchangers are very often assembled from numerous parts joined together to separate heat transfer fluids and to form the required heat exchanger arrangement. Therefore, the leak tightness is very important property of the compact heat exchangers. Although, the compact heat exchangers have been produced for many years, there are still technological problems associated with manufacturing of the ideal connection between the individual parts, mainly encountered with special purpose heat exchangers, e.g. gas turbine recuperators. This paper describes a procedure used to identify the leakage location inside the prime surface gas turbine recuperator. For this purpose, an analytical model of the leaky gas turbine recuperator was created to assess its performance. The results obtained are compared with the experimental data which were acquired during the recuperator thermal performance analysis. The differences between these two data sets are used to indicate possible leakage areas.
Heat pipes in modern heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Vasiliev, L.L. [Academy of Science, Minsk (Russian Federation). A.V. Luikov Heat and Mass Transfer Institute
Heat pipes are very flexible systems with regard to effective thermal control. They can easily be implemented as heat exchangers inside sorption and vapour-compression heat pumps, refrigerators and other types of heat transfer devices. Their heat transfer coefficient in the evaporator and condenser zones is 10{sup 3}-10{sup 5} W/m{sup 2} K, heat pipe thermal resistance is 0.01-0.03 K/W, therefore leading to smaller area and mass of heat exchangers. Miniature and micro heat pipes are welcomed for electronic components cooling and space two-phase thermal control systems. Loop heat pipes, pulsating heat pipes and sorption heat pipes are the novelty for modern heat exchangers. Heat pipe air preheaters are used in thermal power plants to preheat the secondary-primary air required for combustion of fuel in the boiler using the energy available in exhaust gases. Heat pipe solar collectors are promising for domestic use. This paper reviews mainly heat pipe developments in the Former Soviet Union Countries. Some new results obtained in USA and Europe are also included. (author)
Experimental research on heat transfer in a coupled heat exchanger
Liu Yin; Ma Jing; Zhou Guang-Hui; Guan Ren-Bo
The heat exchanger is a devise used for transferring thermal energy between two or more different temperatures. The widespreadly used heat exchanger can only achieve heat exchange between two substances. In this paper, a coupled heat exchanger is proposed, which includes a finned heat exchanger and a double pipe heat exchanger, for multiple heat exchange simultaneously. An experiment is conducted, showing that the average heating capacity increases more tha...
High Temperature Heat Exchanger Project
Energy Technology Data Exchange (ETDEWEB)
Anthony E. Hechanova, Ph.D.
The UNLV Research Foundation assembled a research consortium for high temperature heat exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature heat exchanger componets in hydrogen production processes and design and perform prototypical testing of heat exchangers. The initial research of the consortium focused on the intermediate heat exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These heat exchanger components were deemed the most challenging from a materials performance and compatibility perspective
Experimental and numerical analyses on a plate heat exchanger with phase change for waste heat recovery at off-design conditions
Cipollone, Roberto; Bianchi, Giuseppe; Di Battista, Davide; Fatigati, Fabio
This paper analyzes the performances of an evaporator for small scale waste heat recovery applications based on bottoming Organic Rankine Cycles with net output power in the range 2-5 kW. The heat recovery steam generator is a plate heat exchanger with oil as hot stream and an organic fluid on the cold side. An experimental characterization of the heat exchanger was carried out at different operating points measuring temperatures, pressures and flow rates on both sides. The measurement data further allowed to validate a numerical model of the evaporator whereas heat transfer coefficients were evaluated comparing several literature correlations, especially for the phase-change of the organic fluid. With reference to a waste heat recovery application in industrial compressed air systems, multiple off-design conditions were simulated considering the effects of oil mass flow rate and temperature on the superheating of the organic fluid, a key parameter to ensure a proper operation of the expansion machine, thus of the energy recovery process.
Materials for gasifier heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Kilgallon, P.; Simms, N.J.; Norton, J.F.; Oakey, J.E. [Power Generation Technology Centre, Cranfield Univ. (United Kingdom)
Gasification systems were originally developed to be fired on coal, but there is now interest in co-firing coal with waste or biomass or using low-grade coals and heavy fuel oils in order to reduce environmental impact and fuel costs. All gasification technologies require a heat exchanger between the gasifier and the gas cleaning system. However, gasifier hot gas path environments are potentially very aggressive for materials both during plant operation and downtime periods. The potential corrosive effects of deposits formed on coal-fired and co-fired gasifier heat exchangers in ABGC and IGCC systems have been assessed. Data on the formation of deposits on gasifier heat exchangers have been gathered and a literature survey of downtime corrosion testing relating to gasifier heat exchangers carried out. Laboratory studies have been carried out to investigate the potential response of current and candidate gasifier heat exchanger materials (such as Alloy 800 and Sanicro 28) to such deposits. Electrochemical tests in aqueous solutions are being used to give a ranking of the materials in typical environments anticipated for ABGC and IGCC heat exchangers. A modified EPRI downtime corrosion test has been employed which involves exposing candidate materials covered with a simulated deposit to a humid atmosphere. Preliminary results from baseline tests are given. This work is leading towards the identification of combinations of fuels, operating conditions and materials that could produce rapid heat exchanger failures due to interactions with the deposits formed during operation. (orig.)
Compact heat exchangers modeling: Condensation
Energy Technology Data Exchange (ETDEWEB)
Garcia-Cascales, J.R.; Vera-Garcia, F. [Technical University of Cartagena, Thermal and Fluid Engineering Department, C/Dr. Fleming, s/n 30202 Cartagena, Murcia (Spain); Gonzalvez-Macia, J.; Corberan-Salvador, J.M. [Technical University of Valencia, Applied Thermodynamic Department, Valencia (Spain); Johnson, M.W.; Kohler, G.T. [Modine Manufacturing Company, Commercial Products Group, Racine, WI (United States)
A model for the analysis of compact heat exchangers working as either evaporators or condensers is presented. This paper will focus exclusively on condensation modeling. The model is based on cell discretization of the heat exchanger in such a way that cells are analyzed following the path imposed by the refrigerant flowing through the tubes. It has been implemented in a robust code developed for assisting with the design of compact heat exchangers and refrigeration systems. These heat exchangers consist of serpentine fins that are brazed to multi-port tubes with internal microchannels. This paper also investigates a number of correlations used for the calculation of the refrigerant side heat transfer coefficient. They are evaluated comparing the predicted data with the experimental data. The working fluids used in the experiments are R134a and R410A, and the secondary fluid is air. The experimental facility is briefly described and some conclusions are finally drawn. (author)
Heat exchanger using graphite foam
Campagna, Michael Joseph; Callas, James John
A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.
Materials for gasifier heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Kilgallon, P.; Simms, N.J.; Oakey, J.E. [Cranfield University, Cranfield (United Kingdom). Power Generation Technology Centre
The project has assessed the potential corrosive effects of deposits formed on coal-fired and coal/waste co-fired gasifier fuel-gas/syngas heat exchangers in ABGC and IGCC systems. This has included determining the ranges of deposit compositions formed on heat exchangers with different fuels and quantitatively assessing the effects of such deposits on downtime corrosion (including the effects of potential preventative measures) and synergistic interactions. These activities have lead to the identification of combinations of fuels, operating conditions and materials that could produce rapid heat exchanger failures due to interactions with the deposits formed during the heat exchanger operation. The following candidate gasifier heat exchanger alloys were investigated: AISI 316L, AISI 310, AISI 347H, Alloy 800, Sanicro 28, Haynes 160, Esshete 1250, Haynes 556, IN625, and T23. In terms of cost and performance Sanicro 28 appears to be the best choice for evaporative heat exchangers in the range of test conditions investigated. 48 refs., 59 figs., 28 tabs.
Indoor Solar Thermal Energy Saving Time with Phase Change Material in a Horizontal Shell and Finned-Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
S. Paria
Full Text Available An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF. The focus of this study was on the behavior of PCM for storage (charging or melting and removal (discharging or solidification, as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises.
Indoor solar thermal energy saving time with phase change material in a horizontal shell and finned-tube heat exchanger.
Paria, S; Sarhan, A A D; Goodarzi, M S; Baradaran, S; Rahmanian, B; Yarmand, H; Alavi, M A; Kazi, S N; Metselaar, H S C
An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises. PMID:25879052
Experimental research on heat transfer in a coupled heat exchanger
Directory of Open Access Journals (Sweden)
Liu Yin
Full Text Available The heat exchanger is a devise used for transferring thermal energy between two or more different temperatures. The widespreadly used heat exchanger can only achieve heat exchange between two substances. In this paper, a coupled heat exchanger is proposed, which includes a finned heat exchanger and a double pipe heat exchanger, for multiple heat exchange simultaneously. An experiment is conducted, showing that the average heating capacity increases more than 35%, and the average heating efficiency increases more than 55%, compared with the ordinary air-source heat pump.
A Review of the Experimental and Modeling Development of a Water Phase Change Heat Exchanger for Future Exploration Support Vehicles
Cognata, Thomas; Leimkuehler, Thomas; Ramaswamy, Balasubramaniam; Nayagam, Vedha; Hasan, Mohammad; Stephan, Ryan
Water affords manifold benefits for human space exploration. Its properties make it useful for the storage of thermal energy as a Phase Change Material (PCM) in thermal control systems, in radiation shielding against Solar Particle Events (SPE) for the protection of crew members, and it is indisputably necessary for human life support. This paper envisions a single application for water which addresses these benefits for future exploration support vehicles and it describes recent experimental and modeling work that has been performed in order to arrive at a description of the thermal behavior of such a system. Experimental units have been developed and tested which permit the evaluation of the many parameters of design for such a system with emphasis on the latent energy content, temperature rise, mass, and interstitial material geometry. The experimental results are used to develop a robust and well correlated model which is intended to guide future design efforts toward the multi-purposed water PCM heat exchanger envisioned.
Numerical Study of Solidification in a Plate Heat Exchange Device with a Zigzag Configuration Containing Multiple Phase-Change-Materials
Directory of Open Access Journals (Sweden)
Peilun Wang
Full Text Available Latent heat thermal energy storage (TES plays an important role in the advocation of TES in contrast to sensible energy storage because of the large storage energy densities per unit mass/volume possible at a nearly constant thermal energy. In the current study, a heat exchange device with a zigzag configuration containing multiple phase-change-materials (m-PCMs was considered, and an experimental system was built to validate the model for a single PCM. A two-dimensional numerical model was developed using the ANSYS Fluent 14.0 software program. The energy fractions method was put forward to calculate the average Ste number and the influence of Re and Ste numbers on the discharge process were studied. The influence of phase change temperature among m-PCMs on the solidification process has also been studied. A new boundary condition was defined to determine the combined effect of the Re and Ste numbers on the discharging process. The modelling results show that for a given input power, the Ste (or Re number has a significant impact on the discharging process; however, the period value of inlet velocity has almost no impact on it. Besides, the zigzag plate with m-PCMs has a good impact on the temperature shock as "filter action" in the discharging process.
Didik Wahjudi
Heat exchanger effectiveness is affected by some factors such as pipe shape, temperature, cold and hot air direction and velocity entering the heat exchanger. Research about heat exchanger has been done but the significance level of the heat exchanger effectiveness resulted is unknown. A designed experiment should be done to optimize the performance of concentric tube heat exchanger with measured significance level. From the analysis of result of previous experiment, factors that seem to affe...
Membrane and plastic heat exchangers performance
Masud Behnia; Mohammad Shakir Nasif; Graham L. Morrison
The performance of a membrane-based heat exchanger utilizing porous paper as the heat and moisture transfer media is presented. The measured performance is compared with a plastic film heat exchanger. This novel heat exchanger is used in ventilation energy recovery systems. The results show that the sensible effectiveness is higher than the latent effectiveness. When a similar experiment was conducted using a plastic film heat exchanger surface instead of paper, where only heat is transferred...
Heat exchanger demonstration expert system
Bagby, D. G.; Cormier, R. A.
A real-time expert system intended for detecting and diagnosing faults in a 20 kW microwave transmitter heat exchanger is described. The expert system was developed on a LISP machine, Incorporated (LMI), Lambda Plus computer using Process Intelligent Control (PICON) software. The Heat Exhanger Expert System was tested and debugged. Future applications and extensions of the expert system to transmitters, masers, and antenna subassemblies are discussed.
Heat exchanger with oscillating flow
Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)
Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.
Experimental study on heat exchange of several types of exchangers
Institute of Scientific and Technical Information of China (English)
周志华; 赵振华; 于洋
Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.
Cryogenic Heat Exchanger with Turbulent Flows
Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard
An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…
Optimal design of the separate type heat pipe heat exchanger
Institute of Scientific and Technical Information of China (English)
YU Zi-tao; HU Ya-cai; CEN Ke-fa
Separate type heat pipe heat exchangers are often used for large-scale heat exchanging. The arrangement of such a heat exchanger conveniently allows heat input to and output from the heat exchanger at remote locations. The traditional method of designing an ordinary HPHE (heat pipe heat exchanger) is commonly applied in the separate type exchanger design, but the calculations have to be carried out separately, which makes it very complicated. In this work, the ε-NTU (effectiveness-Number of Transfer Units) method was applied for optimization analysis of single- or multi-level separate type heat pipe heat exchangers. An optimizing formula for single-level separate type heat pipe heat exchangers was obtained. The optimizing principles of effectiveness-NTU and heat transfer rate by the equal distribution method for multi-level separate type heat pipe heat exchanger are presented. The design of separate type heat pipe heat exchangers by the optimizing method is more convenient and faster than by the traditional method.
Fluidized bed heat exchanger utilizing angularly extending heat exchange tubes
Talmud, Fred M.; Garcia-Mallol, Juan-Antonio
A fluidized bed heat exchanger in which air is passed through a bed of particulate material containing fuel disposed in a housing. A steam/water natural circulation system is provided and includes a steam drum disposed adjacent the fluidized bed and a series of tubes connected at one end to the steam drum. A portion of the tubes are connected to a water drum and in the path of the air and the gaseous products of combustion exiting from the bed. Another portion of the tubes pass through the bed and extend at an angle to the upper surface of the bed.
BASIMO - Borehole Heat Exchanger Array Simulation and Optimization Tool
Schulte, Daniel; Rühaak, Wolfram; Welsch, Bastian; Bär, Kristian; Sass, Ingo
Borehole heat exchangers represent a well-established technology, which pushes for new fields of applications and novel modifications. Current simulation tools cannot - or only to some extent - describe features like inclined or partly insulated boreholes unless they run fully discretized models of the borehole heat exchangers. However, fully discretized models often come at a high computational cost, especially for large arrays of borehole heat exchangers. We present a tool, which uses one dimensional thermal resistance and capacity models for the borehole heat exchangers coupled with a numerical finite element model for the subsurface heat transport. An unstructured tetrahedral mesh bypasses the limitations of structured grids for borehole path geometries, while the thermal resistance and capacity model is improved to account for borehole heat exchanger properties changing with depth. The presented tool benefits from the fast analytical solution of the thermal interactions within the boreholes while still allowing for a detailed consideration of the borehole heat exchanger properties.
Mathematical simulation of heat exchanger working conditions
Gavlas Stanislav; Ďurčanský Peter; Lenhard Richard; Jandačka Jozef
One of the When designing a new heat exchanger it is necessary to consider all the conditions imposed on the exchanger and its desired properties. Most often the investigation of heat transfer is to find heat surface. When applying exchanger for proposed hot air engine, it will be a counter-flow heat exchanger of gas - gas type. Gas, which transfers the heat will be exhaust gas from the combustion of biomass. An important step in the design and verification is to analyze exchanger designed us...
A core alternative[Heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Weaver, R.H. [Chart Heat Exchangers, Wisconsin (United States)
The development of the efficient Core-in-kettle heat exchangers by Chart Heat Exchangers as an alternative to shell and tube exchangers is reported, and its use as condensers and reboilers in ethylene plants and refrigerant condensers and chillers in natural gas processing and liquid natural gas (LNG) plants are discussed. The novel technology is described with details given of the replacement of the tube bundle with a Chart brazed aluminium plate-fin heat exchanger core, the operation of the exchanger, the savings achieved by installing these heat exchangers in new or existing plants, and Core-in-Kettle retrofits of existing shell and tube heat exchangers. The limitations of the use of Core-in-Kettle heat exchangers to clean fluids typical of hydrocarbon processing, and temperature and pressure limitations are noted.
Comparison of a Conventional Heat Exchangers with a New Designed Heat Exchanger Experimentally
Directory of Open Access Journals (Sweden)
Tansel Koyun
Full Text Available In this study, the air-water heat exchanger designed have been experimentally compared to conventional heat exchangers with and without fin. The same parameters for the three heat exchangers (pump flow, heating power, etc... have been used. In the experiments, speed-flow adjustment has been made to supply heat transfer at an optimum. As a result, during the circulation of water in pipe of the air-water heat exchanger, the corrosion fouling factor has not been formed. In addition, the efficiency of the new designed heat exchanger has been found between fin and finless heat exchanger efficiencies. The results have been shown in the diagrams.
Rational Efficiency of a Heat Exchanger
McGovern, Jim; Smyth, Brian P.
The authors propose a new and unique definition for the rational efficiency of a heat exchanger. This new rational efficiency is defined in terms of its sub-rational efficiencies: a heat transfer rational efficiency and a friction rational efficiency for each of the fluid systems comprising the heat exchanger. The heat transfer rational efficiency is based on the definition of a mean temperature for the heat source and a mean temperature for the heat sink and reflects the exergy supplied and ...
Discontinuous Operation of Geothermal Heat Exchangers
Institute of Scientific and Technical Information of China (English)
方肇洪; 刁乃仁; 崔萍
Ground-source heat pump (GSHP) systems for HVAC have aroused more and more interest in China in recent years because of their higher energy efficiency compared with conventional systems. The design and performance simulation of the geothermal heat exchangers is vital to the success of this technology. In GSHP systems, the load of the geothermal heat exchanger varies greatly and is usually discontinuous even during a heating or cooling season. This paper outlines a heat transfer model for geothermal heat exchangers. The model was used to study the influence of the discontinuous operation of the heat pumps on the performance of the geothermal heat exchangers. A simple and practical approach is presented for sizing the geothermal heat exchangers.
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.
Testing and analysis of immersed heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Farrington, R.B.; Bingham, C.E.
The objectives were to determine the performance of four immersed, ''supply-side'' heat exchangers used in solar domestic-hot-water systems; to examine the effects of flow rate, temperature difference, and coil configuration on performance; and to develop a simple model to predict the performance of immersed heat exchangers. We tested four immersed heat exchangers: a smooth coil, a finned spiral, a single-wall bayonet, and a double-wall bayonet. We developed two analyticl models and a simple finite difference model. We experimentally verified that the performance of these heat exchangers depends on the flow rate through them; we also showed that the temperature difference between the heat exchanger's inlet and the storage tank can strongly affect a heat exchanger's performance. We also compared the effects of the heat exchanger's configuration and correlated Nusselt and Rayleigh numbers for each heat exchanger tested. The smooth coil had a higher effectiveness than the others, while the double-wall bayonet had a very low effectiveness. We still do not know the long-term effectiveness of heat exchangers regarding scale accumulation, nor do we know the effects of very low flow rates on a heat exchanger's performance.
Design and Development of a Sub-Zero Fluid System for Demonstration of Orion's Phase Change Material Heat Exchangers on ISS
Sheth, Rubik B.; Ahlstrom, Thomas D.; Le, Hung V.
NASA's Orion Multipurpose Crew Vehicle's Exploration Mission 2 is expected to loiter in Lunar orbit for a relatively long period of time. In low Lunar orbit (LLO) the thermal environment is cyclic - extremely cold in the eclipse and relatively hot near the subsolar point. Phase change material heat exchangers (PCM HXs) are the best option for long term missions in these environments. A PCM HX allows a vehicle to store excess waste energy by thawing a phase change material such as n-pentadecane wax. During portions of the orbit that are extremely cold, the excess energy is rejected, resolidifying the wax. Due to the inherent risk of compromising the heat exchanger during multiple freeze and thaw cycles, a unique payload was designed for the International Space Station to test and demonstration the functions of a PCM HX. The payload incorporates the use of a pumped fluid system and a thermoelectric heat exchanger to promote the freezing and thawing of the PCM HX. This paper shall review the design and development undertaken to build such a system.
Comparison of heat transfer efficiency between heat pipe and tube bundles heat exchanger
Wu Zhao-Chun; Zhu Xiang-Ping
A comparison of heat transfer efficiency between the heat pipe and tube bundles heat exchanger is made based on heat transfer principle and the analysis of thermal characteristics. This paper argues that although heat pipe has the feature of high axial thermal conductivity, to those cases where this special function of heat transfer is unnecessary, heat pipe exchanger is not a high efficient heat exchanger when it is just used as a conventional heat exchang...
Micro tube heat exchangers for Space Project
National Aeronautics and Space Administration — Mezzo fabricates micro tube heat exchangers for a variety of applications, including aerospace, automotive racing, Department of Defense ground vehicles,...
High temperature heat exchange: nuclear process heat applications
International Nuclear Information System (INIS)
The unique element of the HTGR system is the high-temperature operation and the need for heat exchanger equipment to transfer nuclear heat from the reactor to the process application. This paper discusses the potential applications of the HTGR in both synthetic fuel production and nuclear steel making and presents the design considerations for the high-temperature heat exchanger equipment
Probe Measures Fouling As In Heat Exchangers
Marner, Wilbur J.; Macdavid, Kenton S.
Combustion deposits reduce transfer of heat. Instrument measures fouling like that on gas side of heat exchanger in direct-fired boiler or heat-recovery system. Heat-flux probe includes tube with embedded meter in outer shell. Combustion gases flow over probe, and fouling accumulates on it, just as fouling would on heat exchanger. Embedded heat-flow meter is sandwich structure in which thin Chromel layers and middle alloy form thermopile. Users determine when fouling approaches unacceptable levels so they schedule cleaning and avoid decreased transfer of heat and increased drop in pressure fouling causes. Avoids cost of premature, unnecessary maintenance.
Conjugate heat and mass transfer in heat mass exchanger ducts
Zhang, Li-Zhi
Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi
Heat exchanger network retrofit through heat transfer enhancement
Wang, Yufei
Heat exchanger network retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often results in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. These probl...
Optimization of parameters of heat exchangers vehicles
Directory of Open Access Journals (Sweden)
Andrei MELEKHIN
Full Text Available The relevance of the topic due to the decision of problems of the economy of resources in heating systems of vehicles. To solve this problem we have developed an integrated method of research, which allows to solve tasks on optimization of parameters of heat exchangers vehicles. This method decides multicriteria optimization problem with the program nonlinear optimization on the basis of software with the introduction of an array of temperatures obtained using thermography. The authors have developed a mathematical model of process of heat exchange in heat exchange surfaces of apparatuses with the solution of multicriteria optimization problem and check its adequacy to the experimental stand in the visualization of thermal fields, an optimal range of managed parameters influencing the process of heat exchange with minimal metal consumption and the maximum heat output fin heat exchanger, the regularities of heat exchange process with getting generalizing dependencies distribution of temperature on the heat-release surface of the heat exchanger vehicles, defined convergence of the results of research in the calculation on the basis of theoretical dependencies and solving mathematical model.
Heat Exchanger Lab for Chemical Engineering Undergraduates
Rajala, Jonathan W.; Evans, Edward A.; Chase, George G.
Third year chemical engineering undergraduate students at The University of Akron designed and fabricated a heat exchanger for a stirred tank as part of a Chemical Engineering Laboratory course. The heat exchanger portion of this course was three weeks of the fifteen week long semester. Students applied concepts of scale-up and dimensional…
Research of characteristics slot-hole heat exchanger with the developed surface of heat exchange
Malkin E. C.; Nikolaenko Yu. E.; Djachkov M. I.; Nikolaienko T. Yu.
Thermal characteristics of multichannel slot-hole heat exchanger with the developed surface of heat exchange inside the opened-cycle water cooling system are experimentally investigated. Graphic dependences of average value of temperature of the simulator of a heat current and temperatures of the heat exchanger base are presented on tapped-off power. Dependences of tapped-off power and hydraulic losses on the of water consumption are given. It is shown, that use of developed slot-hole heat ex...
Applications of artificial neural networks for thermal analysis of heat exchangers - A review
International Nuclear Information System (INIS)
Artificial neural networks (ANN) have been widely used for thermal analysis of heat exchangers during the last two decades. In this paper, the applications of ANN for thermal analysis of heat exchangers are reviewed. The reported investigations on thermal analysis of heat exchangers are categorized into four major groups, namely (i) modeling of heat exchangers, (ii) estimation of heat exchanger parameters, (iii) estimation of phase change characteristics in heat exchangers and (iv) control of heat exchangers. Most of the papers related to the applications of ANN for thermal analysis of heat exchangers are discussed. The limitations of ANN for thermal analysis of heat exchangers and its further research needs in this field are highlighted. ANN is gaining popularity as a tool, which can be successfully used for the thermal analysis of heat exchangers with acceptable accuracy. (authors)
A Review on Heat Transfer Improvent of Plate Heat Exchanger
Abhishek Nandan; Gurpreet Singh Sokhal
Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a la...
Testing and plugging power plant heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Sutor, F. [Expando Seal Tools, Inc., Montgomeryville, PA (United States)
Heat Exchanger tubes fail for any number of reasons including but certainly not limited to the cumulative effects of corrosion, erosion, thermal stress and fatigue. This presentation will attempt to identify the most common techniques for determining which tubes are leaking and then introduce the products in use to plug the leaking tubes. For the sake of time I will limit the scope of this presentation to include feedwater heaters and secondary system heat exchangers such as Hydrogen Coolers, Lube Oil Coolers, and nuclear Component Cooling Water, Emergency Cooling Water, Regenerative Heat Recovery heat exchangers.
Experimental Evaluation of a Paraffin as Phase Change Material for Thermal Energy Storage in Laboratory Equipment and in a Shell-and-Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
Jaume Gasia
Full Text Available The thermal behavior of a commercial paraffin with a melting temperature of 58 °C is analyzed as a phase change material (PCM candidate for industrial waste heat recovery and domestic hot water applications. A full and complete characterization of this PCM is performed based on two different approaches: a laboratory characterization (mass range of milligrams and an analysis in a pilot plant (mass range of kilograms. In the laboratory characterization, its thermal and cycling stability, its health hazard as well as its phase change thermal range, enthalpy and specific heat are analyzed using a differential scanning calorimeter, thermogravimetric analysis, thermocycling and infrared spectroscopy. Laboratory analyses showed its suitability up to 80 °C and for 1200 cycles. In the pilot plant analysis, its thermal behavior was analyzed in a shell-and-tube heat exchanger under different heat transfer fluid mass flow rates in terms of temperature, power and energy rates. Results from the pilot plant analysis allowed understanding the different methods of heat transfer in real charging and discharging processes as well as the influence of the geometry of the tank on the energy transferred and required time for charging and discharging processes.
Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger
Directory of Open Access Journals (Sweden)
Pavel Neuberger
Full Text Available Temperature changes and heat flows in soils that host "slinky"-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity of the thermal energy content of the soil to regenerate when the heat exchangers are not operating. Analysis of specific heat flows and the specific thermal energy regime within the soil, including that captured by the heat-exchangers, has been characterised by meticulous measurements. These reveal that high concentrations of antifreeze mix in the heat-transfer fluid of the heat exchanger have an adverse impact on heat flows discharged into the soil.
Synthesis of Heat Exchanger Network Considering Multipass Exchangers
Institute of Scientific and Technical Information of China (English)
李绍军; 姚平经
Many methods have been proposed for synthesis of heat exchanger networks in recent years, most of which consider single pass exchangers. In this study some evolutionary rules have been proposed for synthesis of multipass exchanger networks. The method is based on the heuristic that optimal networks should feature maximum energy recovery and have the minimum number of shells. The effectiveness of the developed evolutionary rules is demonstrated through some literature examples.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
40 CFR 63.1409 - Heat exchange system provisions.
... locations where the cooling water enters and exits each heat exchanger or any combination of heat exchangers.... (iii) For samples taken at the entrance and exit of each heat exchanger or any combination of heat exchangers, the entrance is the point at which the cooling water enters the individual heat exchanger...
Comparison of a Conventional Heat Exchangers with a New Designed Heat Exchanger Experimentally
Tansel Koyun; Semih Avcı
In this study, the air-water heat exchanger designed have been experimentally compared to conventional heat exchangers with and without fin. The same parameters for the three heat exchangers (pump flow, heating power, etc...) have been used. In the experiments, speed-flow adjustment has been made to supply heat transfer at an optimum. As a result, during the circulation of water in pipe of the air-water heat exchanger, the corrosion fouling factor has not been formed. In addition, the efficie...
Sleeving repair of heat exchanger tubes
International Nuclear Information System (INIS)
Defective heat exchanger tubes can be repaired using techniques that do not involve the cost and schedule penalties of component replacement. FTI's years of experience repairing steam generator tubes have been successfully applied to heat exchangers. Framatome Technologies heat exchanger sleeves can bridge defective areas of the heat exchanger tubes, sleeves have been designed to repair typical heat exchanger tube defects caused by excessive tube vibration, stress corrosion cracking, pitting or erosion. By installing a sleeve, the majority of the tube's heat transfer and flow capacity is maintained and the need to replace the heat exchanger can be delayed or eliminated. Both performance and reliability are improved. FTI typically installs heat exchanger tube sleeves using either a roll expansion or hydraulic expansion process. While roll expansion of a sleeve can be accomplished very quickly, hydraulic expansion allows sleeves to be installed deep within a tube where a roll expander cannot reach. Benefits of FTI's heat exchanger tube sleeving techniques include: - Sleeves can be positioned any where along the tube length, and for precise positioning of the sleeve eddy current techniques can be employed. - Varying sleeve lengths can be used. - Both the roll and hydraulic expansion processes are rapid and both produce joints that do not require stress relief. - Because of low leak rates and speed of installations, sleeves can be used to preventatively repair likely-to-fail tubes. - Sleeves can be used for tube stiffening and to limit leakage through tube defects. - Because of installation speed, there is minimal impact on outage schedules and budgets. FTI's recently installed heat exchanger sleeving at the Kori-3 Nuclear Power Station in conjunction with Korea Plant Service and Engineering Co., Ltd. The sleeves were installed in the 3A and 3B component cooling water heat exchangers. A total of 859 tubesheet and 68 freespan sleeves were installed in the 3A heat
Analysis of a Flooded Heat Exchanger
Fink, Aaron H.; Luyben, William L.
Flooded heat exchangers are often used in industry to reduce the required heat-transfer area and the size of utility control valves. These units involve a condensing vapor on the hot side that accumulates as a liquid phase in the lower part of the vessel. The heat transfer occurs mostly in the vapor space, but the condensate becomes somewhat…
Thermodynamic Optimization of GSHPS Heat Exchangers
Directory of Open Access Journals (Sweden)
Ahmad Kahrobaeian
Full Text Available
In this paper, a new method for determining the optimized dimensions of a ground source heat pump system (GSHPS heat exchanger is presented. Using the GSHPS is one of the ways for utilization of infinite, clean and renewable energies in the environment. In recent years, due to limitation of physical space for installing the heat exchangers and avoiding the environmental effects on heat exchanger operation, vertical GSHP systems are used more than the other ones. Determination of optimum heat exchanger size is one of the most important parameters in the optimization of the heat exchanger design. In this study, optimum length and diameter for the heat exchanger is determined for different mass flows by using the second law of thermodynamics. The optimal length and diameter minimize entropy generation and therefore result in increased efficiency of the heat pump.
Vibration isolation of dimple plate heat exchangers / Pieter Vergeer
Vergeer, Pieter
Dimple plate heat exchangers are a new type of welded compact plate heat exchangers. The dimple plates increase the turbulence of the fluid flowing over the plate, increasing the efficiency of the heat exchanger without increasing pressure drop over the heat exchanger. The compact design of the heat exchanger makes it possible to install the heat exchanger at the top of condenser columns, reducing the footprint area of the column by replacing standard shell and tube condense...
Lightweight Thermal Storage Heat Exchangers Project
National Aeronautics and Space Administration — This SBIR proposal aims to develop thermal energy storage heat exchangers that are significantly lighter and higher conductance than the present art which involves...
Heat exchanger tube inspection using ultrasonic arrays
International Nuclear Information System (INIS)
Tubing used in industrial heat exchangers is often subject to failure caused by corrosion and cracking. Technical conferences are used as a forum in the steam generator industry to ensure that the failure mechanisms are well understood and that the quality of the heat exchanger is maintained. The quality of a heat exchanger can be thought of as its ability to operate to design specifications over its intended life. This is the motivation to inspect and evaluate these devices periodically. Inspection, however, normally requires shutdown of the heat exchanger which is costly but is much more acceptable than an unscheduled shutdown due to failure of a tube. Therefore, the degree of inspection is established by balancing the cost of inspection with the risk of a tube failure. Any method of reducing the cost of inspection will permit a higher degree of inspection and, therefore, improve heat exchanger quality. This paper reviews the design and performance of an improved method of ultrasonic inspection of heat exchanger tubing with emphasis on applications in the nuclear industry
Heat transfer from oriented heat exchange areas
Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej
This paper deals with the transfer of heat-driven heat transfer surface area in relation to the construction of the criterion equation for "n" horizontal pipe one about another. On the bases of theoretical models have been developed for calculating the thermal performance of natural convection by Churilla and Morgan, for various pipe diameters and temperatures. These models were compared with models created in CFD-Fluent Ansys the same boundary conditions. The aim of the analyse of heat and fluxional pipe fields "n" pipes one about another at natural convection is the creation of criterion equation on the basis of which the heat output of heat transfer from pipe oriented areas one above another with given spacing could be quantified. At presence a sum of criterion equations exists for simple geometrical shapes of individual oriented geometrical areas but the criterion equation which would consider interaction of fluxional field generated by free convection from multiple oriented areas is not mentioned in standardly accessible technical literature and other magazine publications.
Flow and heat transfer enhancement in tube heat exchangers
Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Ekadewi Anggraini Handoyo
In a heat exchanger, there is heat transferred either from the surrounding or to the surrounding, which is not expected. A thermal insulator is used to reduce this heat transfer. The effectiveness of a heat exchanger will increase if the heat loss to surrounding can be reduced. Theoretically, the thicker the insulator the smaller the heat loss in a plate heat exchanger. A research is carried on to study the effect of an insulator thickness on heat exchanger effectiveness. The insulators used ...
Near Field Investigation of Borehole Heat Exchangers
Erol, Selcuk
As an alternative and renewable energy source, the shallow geothermal energy evolving as one of the most popular energy source due to its easy accessibility and availability worldwide, and the ground source heat pump (GSHP) systems are the most frequent applications for extracting the energy from the shallow subsurface. As the heat extraction capacity of the GSHP system applications arises, the design of the borehole heat exchangers (BHE), which is the connected part of the system in the grou...
The dry heat exchanger calorimeter system
International Nuclear Information System (INIS)
A radiometric isothermal heat flow calorimeter and preconditioner system that uses air instead of water as the heat exchange medium has been developed at Mound. The dry heat exchanger calorimeter is 42 inches high by 18 inches in diameter and the preconditioner is a 22 inch cube, making it extremely compact compared to existing units. The new system is ideally suited for transportable, stand-alone, or glovebox applications. Preliminary tests of the system have produced sample measurements with standard deviations less than 0.25% and sample errors less than 0.50%. These tests have shown that the dry heat exchanger system will yield acceptance data with an accuracy comparable to those of Mound water bath systems now in use. 4 figs., 1 tab
Performance Investigation of Plate Type Heat Exchanger (A Case Study)
Simarpreet Singh; Sanjeev Jakhar
Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness ...
Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger
Pavel Neuberger; Radomír Adamovský; Michaela Šeďová
Temperature changes and heat flows in soils that host "slinky†-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity of the thermal energy content of the soil to regenerate when the heat exchangers are not operating. Analysis of specific heat flows and the specific thermal energy regime within the soil, including that captured by ...
14 CFR 29.1125 - Exhaust heat exchangers.
... exchangers. For reciprocating engine powered rotorcraft the following apply: (a) Each exhaust heat exchanger... is subject to contact with exhaust gases; and (4) No exhaust heat exchanger or muff may have stagnant... an exhaust heat exchanger is used for heating ventilating air used by personnel— (1) There must be...
21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass heat exchanger. 870.4240... bypass heat exchanger. (a) Identification. A cardiopulmonary bypass heat exchanger is a device, consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...
14 CFR 25.1125 - Exhaust heat exchangers.
... exchangers. For reciprocating engine powered airplanes, the following apply: (a) Each exhaust heat exchanger... provisions wherever it is subject to contact with exhaust gases; and (4) No exhaust heat exchanger or muff... carrying flammable fluids. (b) If an exhaust heat exchanger is used for heating ventilating air— (1)...
Simulation of induction heating process with radiative heat exchange
Directory of Open Access Journals (Sweden)
A. Kachel
Full Text Available Purpose: Numerical modelling of induction heating process is a complex issue. It needs analysis of coupled electromagnetic and thermal fields. Calculation models for electromagnetic field analysis as well as thermal field analysis need simplifications. In case of thermal field calculations, correct modelling of radiative heat exchange between the heated charge and inductor's thermal insulation is essential. Most commercial calculation programs enabling coupled analysis of electromagnetic and thermal fields do not allow taking into consideration radiative heat exchange between calculation model components, which limits thermal calculations only to the charge area. The paper presents a supplementation of the program Flux 2D with radiative heat exchange procedures.Design/methodology/approach: Commercial program Flux 2D designed for coupled electromagnetic and thermal calculation (based on finite element method was supplemented with authors program for radiative heat exchange based on numerical integration of classic equations.Findings: Supplementation EM-T calculations with radiative heat exchange between charge and inductor enables to calculate thermal insulation parameters and increase precision of modelling.Research limitations/implications: Procedures for radiative heat exchange enables calculation of two surfaces (flat or cylindrical with finite dimensions. The surfaces can be displaced relative to each other (charge shorter or longer than thermal insulation of inductor. Material of surfaces is modelled as: flat, diffuse, radiant surfaces absorb energy evenly in the whole spectrum (grey bodies. The whole system is modelled as in a steady thermal state (quasi-steady.Originality/value: Authors program extends Flux 2D features with a possibility for calculating radiative heat transfer. The application of radiative process is possible between all components of the studied model, not only for the boundary conditions.
V.NATARAJAN,; Dr. P. Senthil Kumar
This paper focused on the investigational cram of the recital characteristics of tube-in-tube compact heat exchangers. Experiments are conducted in the compact heat exchangers with R-134a and liquefiedpetroleum gas. The effectiveness of the heat exchangers was calculated using the experiment data and it was found that the effectiveness of heat exchanger-1 is above 75 and heat exchanger-2 is above 84% for R-134a.The effectiveness of heat exchanger-1 is about 60% and heat exchanger-2 is about 8...
Ambient temperature effect on changes in heat exchange and skin and coat thermoisolation induced with nembutal in guinea pigs.
Laszczyńska, J
The experiment was carried out on adult male guinea pigs not adapted to cold at temperatures of 29 degrees, 20 degrees and 12 degrees C. During 150 minutes after nembutal injection the following values were recorded: oxygen consumption, subcutaneous, cutaneous and hair-coat temperatures. Using Hatfield's disc heat loss from the body surface by radiation and convection was measured. Nembutal not only inhibited thermogenetic processes at low ambient temperature, but decreased also heat production in a thermoneutral environment. This effect increased with decreasing ambient temperature. At the same time, there was a reduction in heat loss, although in a lower degree. The final result was a fall of the rectal temperature (even by 10 degrees C in a cold environment). Following nembutal administration skin thermoinsulation decreased slightly but the thermoinsulating activity of the hair-coat increased (the pilomotor response was more pronounced than in waking animals). Thermoregulation disturbances induced by nembutal included mainly thermogenesis impairment. The effect of general anaesthesia on heat loss was without any greater importance for maintenance of thermic homeostasis of the organism. PMID:6675430
PS1 satellite refrigerator heat exchanger: Failure of the LN2 heat exchanger to low pressure helium
International Nuclear Information System (INIS)
The PS1 heat exchanger is one of three prototype heat exchangers built by Atomic Welders before Meyer was given the contract to build the Satellite Refrigerator Heat Exchanger components. This heat exchanger was first put into operation in July 1983. In November 1991, this heat exchanger experienced a failure in the shell of heat exchanger 1 causing nitrogen to contaminate the helium in the refrigerator. The resulting contamination plugged heat exchanger 3. The break occurred at a weld that connects a 0.25 inch thick ring to heat exchanger 1. The failure appears to be a fatigue of the shell due to temperature oscillations. The flow rate through the break was measured to be 1.0 scfm for a pressure drop over the crack of 50 psi. An ANSYS analysis of the failure area indicates that the stress would be 83,000 psi if the metal did not yield. This is based on cooling down the shell to 80K from 300K with the shell side helium on the outside of the shell at 300K. This is the largest change in temperature that occurs during operation. During normal operations, the temperature swings are not nearly this large, however temperatures down to 80K are not unusual (LN2 overflowing pot). The highest temperatures are typically 260K. The analysis makes no attempt to estimate the stress concentration factor at this weld but there is no doubt that it is greater than 1. No estimate as to the number of cycles to cause failure was calculated nor any estimate as to the actual number of cycles was made
PS1 satellite refrigerator heat exchanger: Failure of the LN2 heat exchanger to low pressure helium
Squires, B.
The PS1 heat exchanger is one of three prototype heat exchangers built in support of a contract for Satellite Refrigerator Heat Exchanger components. This heat exchanger was first put into operation in Jul. 1983. In Nov. 1991, this heat exchanger experienced a failure in the shell of heat exchanger 1 causing nitrogen to contaminate the helium in the refrigerator. The resulting contamination plugged heat exchanger 3. The break occurred at a weld that connects a 0.25 inch thick ring to heat exchanger 1. The failure appears to be a fatigue of the shell due to temperature oscillations. The flow rate through the break was measured to be 1.0 scfm for a pressure drop over the crack of 50 psi. An ANSYS analysis of the failure area indicates that the stress would be 83,000 psi if the metal did not yield. This is based on cooling down the shell to 80K from 300K with the shell side helium on the outside of the shell at 300K. This is the largest change in temperature that occurs during operation. During normal operations, the temperature swings are not nearly this large, however temperatures down to 80K are not unusual (LN2 overflowing pot). The highest temperatures are typically 260K. The analysis makes no attempt to estimate the stress concentration factor at this weld, but there is no doubt that it is greater than 1. No estimate as to the number of cycles to cause failure was calculated nor any estimate as to the actual number of cycles was made.
Zhu, W; Gianchandani, Yogesh B.; Nellis, G. F.; Klein, Sanford A.
Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920) International audience This paper describes a lithography-based microfabrication process developed for a recuperative heat exchanger intended for use in a cryosurgical probe. The probe, which uses the Joule-Thomson (JT) cooling cycle, must achieve a temperature < -50°C, with a freeze rate of 25-50°C/min. The heat exchanger must maintain high stream-to-stream thermal conductance while restricting...
Carbon nanotube heat-exchange systems
Hendricks, Terry Joseph; Heben, Michael J.
A carbon nanotube heat-exchange system (10) and method for producing the same. One embodiment of the carbon nanotube heat-exchange system (10) comprises a microchannel structure (24) having an inlet end (30) and an outlet end (32), the inlet end (30) providing a cooling fluid into the microchannel structure (24) and the outlet end (32) discharging the cooling fluid from the microchannel structure (24). At least one flow path (28) is defined in the microchannel structure (24), fluidically connecting the inlet end (30) to the outlet end (32) of the microchannel structure (24). A carbon nanotube structure (26) is provided in thermal contact with the microchannel structure (24), the carbon nanotube structure (26) receiving heat from the cooling fluid in the microchannel structure (24) and dissipating the heat into an external medium (19).
Modelling Heat Exchangers for Domestic Boilers
Directory of Open Access Journals (Sweden)
S. F. C. F. Teixeira
Full Text Available In the present paper the thermal behaviour of fin-tube heat exchangers is modeled. Particular attention has been given to the plate fins. The heat fluxes in the fins are described using a finite volume technique to discretize the energy equation. The thermal interactions with the water in the tubes and the surrounding air are treated as external boundaries, using appropriate relationships for forced convection in pipes and flat plates. The numerical results are presented in terms of dimensionless numbers (Fourier, Biot and geometric ratios which are found to be representative for this particular geometry. Furthermore, the effect of thermal gradients along the fin surface upon the fin efficiency is investigated. Based on a differential model for the heat balances, design charts have been developed for the thermal analysis of heat exchangers.
Compact ground heat exchangers in Sweden
Energy Technology Data Exchange (ETDEWEB)
Hellstroem, G. [Dept. of Mathematical Physics, Lund Univ. (Sweden); Rosen, B. [Swedish Geotechnical Inst., Linkoeping (Sweden)
About 30,000 ground-coupled heat pumps are currently installed each year in Sweden. Of these, 70-80% use vertical boreholes rock, whereas the remaining part uses horizontal loops. Vertical boreholes are considered to be a technically safer installation, since there is little risk of accidental damage to the pipes. The house owners also appreciate that there is less impact of excavation and possible frost heave in their garden. A research project aimed at developing compact shallow ground heat exchangers was started in 2001 as a cooperation between Lund University and the Swedish Geotechnical Institute funded by the Swedish Research Council FORMAS and the Swedish Energy Agency. The purpose is to reduce the ground area and the trench length required for installation of cost-effective ground heat exchangers in soil to be used in Swedish climatic and geological conditions. The project is carried out in cooperation with installers and heat pump manufacturers. (orig.)
Micro-Scale Regenerative Heat Exchanger
Moran, Matthew E.; Stelter, Stephan; Stelter, Manfred
A micro-scale regenerative heat exchanger has been designed, optimized and fabricated for use in a micro-Stirling device. Novel design and fabrication techniques enabled the minimization of axial heat conduction losses and pressure drop, while maximizing thermal regenerative performance. The fabricated prototype is comprised of ten separate assembled layers of alternating metal-dielectric composite. Each layer is offset to minimize conduction losses and maximize heat transfer by boundary layer disruption. A grating pattern of 100 micron square non-contiguous flow passages were formed with a nominal 20 micron wall thickness, and an overall assembled ten-layer thickness of 900 microns. Application of the micro heat exchanger is envisioned in the areas of micro-refrigerators/coolers, micropower devices, and micro-fluidic devices.
Heat transfer study of a two-phase refrigerant with liquid-solid phase change inside a smooth plates heat exchanger; Etude des transferts de chaleur d'un fluide frigoporteur diphasique a changement de phase liquide-solide dans un echangeur a plaques lisses
Energy Technology Data Exchange (ETDEWEB)
Demasles, H.
The purpose of the work is to study two-phase mixture heat exchange composed of water particles suspended in silicone oil circulating in a closed loop. Water, contained in polymer porous matrix, is freezing by successive passages in plane plate heat exchanger. Thermo-hydraulic literature data analysis about these fluids in exchangers shows important blanks in exchange coefficient and pressure drop forecast methods and in experimental data. Experimental results, issued of global energy balance on a test section specifically conceived and made for this study, show doping effect on exchange coefficient. Before phase change, micro-convective effects of rotating particles improve exchange coefficient of 2,3 factor. Supplementary enhancement included between 2 and 16 appeared during phase change. Trial measured discrepancy are certainly induced by bed layer formation due to low flow speed. At the end of particle freezing, when latent heat is not involved anymore in exchange enhancement, important heat transfer reduction is observed. This is attributed to the cooling suspension rheological evolution and the change of flow particle distribution. Modelling results corroborate heat exchange improvement due to phase change: particles act as sources when discharging there latent heat. They stop fluid temperature dropping and enable to keep a high wall temperature gradient. A deepened suspension rheological study is necessary for a better understanding of observed phenomenon, nevertheless these first results show already an important energetic profit brings by particles in range temperature of 0 and -6 deg C. (author)
Exergo-ecological evaluation of heat exchanger
Directory of Open Access Journals (Sweden)
Stanek Wojciech
Full Text Available Thermodynamic optimization of thermal devices requires information about the influence of operational and structural parameters on its behaviour. The interconnections among parameters can be estimated by tools such as CFD, experimental statistic of the deviceetc. Despite precise and comprehensive results obtained by CFD, the time of computations is relatively long. This disadvantage often cannot be accepted in case of optimization as well as online control of thermal devices. As opposed to CFD the neural network or regression is characterized by short computational time, but does not take into account any physical phenomena occurring in the considered process. The CFD model of heat exchanger was built using commercial package Fluent/Ansys. The empirical model of heat exchanger has been assessed by regression and neural networks based on the set of pseudo-measurements generated by the exact CFD model. In the paper, the usage of the developed empirical model of heat exchanger for the minimisation of TEC is presented. The optimisationconcerns operational parameters of heat exchanger. The TEC expresses the cumulative exergy consumption of non-renewable resources. The minimization of the TEC is based on the objective function formulated by Szargut. However, the authors extended the classical TEC by the introduction of the exergy bonus theory proposed by Valero. The TEC objective function fulfils the rules of life cycle analysis because it contains the investment expenditures (measured by the cumulative exergy consumption of non-renewable natural resources, the operation of devices and the final effects of decommissioning the installation.
A Ceramic Heat Exchanger for Solar Receivers
Robertson Jr., C.; Stacy, L.
Design intended for high-temperature service. Proposed ceramic-tube and header heat exchangers used for solar-concentrating collector operating in 25- to 150-KW power range at temperatures between 2,000 degrees and 3,000 degrees F (1,095 degrees and 1,650 degrees C).
Exergy-Economic Criteria for Evaluating Heat Exchanger Performance
Institute of Scientific and Technical Information of China (English)
Wu Shuangying; Li Yourong
Based on the exergy-economic analysis of heat exchanger heat transfer and flow process, two new exergyeconomic criteria which are defined as the total costs per unit heat transfer rate ηt t for heat transfer exchanger and the net profit per unit heat recovery rate ηr for heat recovery exchanger respectively are put forward.Furthermore, the application of criteria is illustrated by the evaluation of down-flow, counter-flow and cross-flow heat exchangers performance. The methods employed and results presented in this paper can serve as a guide for the performance evaluation of heat exchangers.
Geothermal heat exchanger with coaxial flow of fluids
Directory of Open Access Journals (Sweden)
Pejić Dragan M.
Full Text Available The paper deals with a heat exchanger with coaxial flow. Two coaxial pipes of the secondary part were placed directly into a geothermal boring in such a way that geothermal water flows around the outer pipe. Starting from the energy balance of the exchanger formed in this way and the assumption of a study-state operating regime, a mathematical model was formulated. On the basis of the model, the secondary circle output temperature was determined as a function of the exchanger geometry, the coefficient of heat passing through the heat exchange areas, the average mass isobaric specific heats of fluid and mass flows. The input temperature of the exchanger secondary circle and the temperature of the geothermal water at the exit of the boring were taken as known values. Also, an analysis of changes in certain factors influencing the secondary water temperature was carried out. The parameters (flow temperature of the deep boring B-4 in Sijarinska Spa, Serbia were used. The theoretical results obtained indicate the great potential of this boring and the possible application of such an exchanger.
Sandeep S. Samane*, Sudhakar S. Umale
Heat Exchangers are used to transfer heat effectively from one medium to another medium. There are several aspects to study the performance of heat exchanger. This paper is concerned with thermo-mechanical issues i.e. thermal expansion due to high temperature and high pressure conditions of U-tube heat exchanger. Tubesheet is very complex part of heat exchanger which expands at high temperature. Due to high temperature difference between shell side and channel side fluids thermal stress are g...
Teaching Heat Exchanger Network Synthesis Using Interactive Microcomputer Graphics.
Dixon, Anthony G.
Describes the Heat Exchanger Network Synthesis (HENS) program used at Worcester Polytechnic Institute (Massachusetts) as an aid to teaching the energy integration step in process design. Focuses on the benefits of the computer graphics used in the program to increase the speed of generating and changing networks. (TW)
Heat exchangers with several heat exchanger matrices mounted in a common casing for separately conducted media
International Nuclear Information System (INIS)
The heat exchanger is suited for plants with a closed gas cycle such as, e. g., HTR with a helium turbine or drive units for vehicles. It contains heat exchanger matrices running parallel to each other and formed by the folds of a uniformly folded band and by walls covering the saddles of the folds. Two neighbouring matrices each are combined to form a heat exchanger unit and supported between supporting walls. The heat exchanger unit is not firmly connected with these supporting walls and therefore can easily to be inserted or dismounted. For sealing purposes, the fold saddles are contacting the supporting walls because of the high pressure of the meUWIdium, Ior the remaining seals between hp and lp-compartments labyrinth boxes being provided. (UWI)
Air duct heat exchanger; Luftkanal-Waermetauscher
Energy Technology Data Exchange (ETDEWEB)
Huber, H.; Helfenfinger, D. [Berner Fachhochschule, Hochschule fuer Technik und Architektur (HTA), Lucerne (Switzerland); Manz, H. [EMPA Eidgenoessischen Materialpruefungs- und Forschungsanstalt, Duebendorf (Switzerland)
A mechanical building ventilation unit that brings together two functions - fluid transport and heat recovery - is presented. Aluminium fins in the supply air duct and in the adjacent extract air duct increase the heat flow from fluid to fluid. This unit is mainly intended to be used for residential ventilation and was investigated by means of experiments and simulations. Air flow rates, temperatures, air humidities and pressure differences were measured in an experimental set-up. Additionally, using a program for two-dimensional heat conduction analyses and a simple model, the efficiency of the heat recovery was calculated and compared with measurements. Afterwards, the influence of variations of the heat exchanger geometry was investigated by means of simulations. It was shown that by using this concept, it is possible to realise a ventilation unit in which heat is exchanged with high efficiency, e.g. temperature efficiency of 0.7 at a duct length of 6 m. At the same time, low pressure-drops occur, typically 20 Pa, which leads to low rates of electrical energy input. (author)
Investigation of heat exchanger inclination in forced-draught air-cooled heat exchangers
Kennedy, I.J.; Spence, S.W.T.; Spratt, G.R.; Early, J. M.
The purpose of this study is to determine the influence of inclining the heat exchanger relative to the fan in a forced draught air-cooled heat exchanger. Since inclination increases plenum depth, the effect of inclination is also compared with increasing plenum depth without inclination. The experimental study shows that inclination improves thermal performance by only 0.5%, when compared with a baseline non-inclined case with a shallow plenum. Similarly, increasing plenum depth without incl...
F.S. LIPORACE; F.L.P. Pessoa; E.M. Queiroz
Recently, a new software (AtHENS) that automatically synthesizes a heat exchanger network with minima consumption of utilities was developed. This work deals with the next step, which represents the evolution of the initial network. Hence, new procedures to identify and break loops are incorporated, for which a new algorithm is proposed. Also, a heat exchanger design procedure which uses the available pressure drop to determine the film coefficient on the tube side and shell side is added, pr...
Materials, Turbomachinery and Heat Exchangers for Supercritical CO2 Systems
Energy Technology Data Exchange (ETDEWEB)
Anderson, Mark; Nellis, Greg; Corradini, Michael
The objective of this project is to produce the necessary data to evaluate the performance of the supercritical carbon dioxide cycle. The activities include a study of materials compatibility of various alloys at high temperatures, the heat transfer and pressure drop in compact heat exchanger units, and turbomachinery issues, primarily leakage rates through dynamic seals. This experimental work will serve as a test bed for model development and design calculations, and will help define further tests necessary to develop high-efficiency power conversion cycles for use on a variety of reactor designs, including the sodium fast reactor (SFR) and very high-temperature gas reactor (VHTR). The research will be broken into three separate tasks. The first task deals with the analysis of materials related to the high-temperature S-CO{sub 2} Brayton cycle. The most taxing materials issues with regard to the cycle are associated with the high temperatures in the reactor side heat exchanger and in the high-temperature turbine. The system could experience pressures as high as 20MPa and temperatures as high as 650°C. The second task deals with optimization of the heat exchangers required by the S-CO{sub 2} cycle; the S-CO{sub 2} flow passages in these heat exchangers are required whether the cycle is coupled with a VHTR or an SFR. At least three heat exchangers will be required: the pre-cooler before compression, the recuperator, and the heat exchanger that interfaces with the reactor coolant. Each of these heat exchangers is unique and must be optimized separately. The most challenging heat exchanger is likely the pre-cooler, as there is only about a 40°C temperature change but it operates close to the CO{sub 2} critical point, therefore inducing substantial changes in properties. The proposed research will focus on this most challenging component. The third task examines seal leakage through various dynamic seal designs under the conditions expected in the S-CO{sub 2} cycle
Thermal induced flow oscillations in heat exchangers for supercritical fluids
Friedly, J. C.; Manganaro, J. L.; Krueger, P. G.
Analytical model has been developed to predict possible unstable behavior in supercritical heat exchangers. From complete model, greatly simplified stability criterion is derived. As result of this criterion, stability of heat exchanger system can be predicted in advance.
Multi-Purpose Logistics Module (MPLM) Cargo Heat Exchanger
Zampiceni, John J.; Harper, Lon T.
This paper describes the New Shuttle Orbiter's Multi- Purpose Logistics Modulo (MPLM) Cargo Heat Exchanger (HX) and associated MPLM cooling system. This paper presents Heat Exchanger (HX) design and performance characteristics of the system.
Conceptualizations for cleaning OTEC heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Rice, M.S.; Hagel, D.; Conn, A.F.
A critical operating aspect of Ocean Thermal Energy Conversion (OTEC) plants is the maintenance of clean surfaces on the seawater-side of the heat exchangers. The objective of this program was to assess the state of the art of biofouling control techniques and to evaluate the potential of these existing methods for solving the biofouling problems in the OTEC system. The first task of the program involved an in-depth review and discussion of various fouling control methods including water treatment, surface conditioning, and cleaning techniques. The methods considered applicable to OTEC were identified. This volume summarizes the second task of the program. The compatibility of the various cleaning and fouling control techniques with the different proposed heat exchanger designs and materials are discussed. Also provided are conceptual illustrations for adapting and incorporating the methods into an OTEC power plant. These conceptual designs suggest means for overcoming some of the shortcomings of the techniques which are considered suitable, however, detailed designs of the modified systems are beyond the scope of this report. Chlorination, chemical cleaning, Amertap recirculating sponge rubber balls, and MAN flow-driven brushes are the methods considered applicable for tubular heat exchangers with seawater inside the tubes. Water jets are suggested for the open-cycle and the ''trombone'' (Applied Physics Laboratory) heat exchanger designs. Although none of the methods are immediately applicable to OTEC in their present configuration, in several cases only minor developmental efforts should produce designs which can satisfy the stringent OTEC cleanliness requirements. Further research and development appear warranted for a number of other methods which indicate promise for long-range applicability. Specific recommendations are included.
Performance Investigation of Plate Type Heat Exchanger (A Case Study
Directory of Open Access Journals (Sweden)
Simarpreet Singh
Full Text Available Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness factor. In process plants, this type of heat exchange is generally used for recovering heat content of exhaust steam. However, with the flow of fluid for a long period, fouling occurs on the plate surface. Therefore, it is required to investigate the effect of fouling, wherever the heat exchanger is installed. An extensive experimental investigation has been carried out under clean and dirty condition of the said plate type heat exchanger. Heat transfer and flow data were collected in experiment. From collected data heat transfer rate, overall heat transfer coefficient, fouling factor and cleanliness factor were evaluated. Based upon the cleanliness factor data, next date of cleanliness for plate type heat exchanger was predicted. It is felt that the outcome of the present research work may be quite useful for efficient operation of plate type heat exchanger installed in Process plants.
14 CFR 23.1125 - Exhaust heat exchangers.
...) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia, and... cooling provisions wherever it is subject to contact with exhaust gases. (b) Each heat exchanger used for... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Exhaust heat exchangers. 23.1125 Section...
Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors
International Nuclear Information System (INIS)
Highlights: • Compact heat exchanger designs evaluated for advanced nuclear reactor applications. • Wavy channel PCHE compared with offset strip-fin heat exchanger (OSFHE). • 15° pitch angle wavy channel PCHE offers optimum performance characteristics. • OSFHE exhibits higher pressure drop and lower compactness than other options. • Comparison technique applicable for evaluating candidate heat exchangers designs. - Abstract: A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimum combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well
A heat transfer model of a horizontal ground heat exchanger
Mironov, R. E.; Shtern, Yu. I.; Shtern, M. Yu.; Rogachev, M. S.
Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn't any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows that heat transfer rates decreases rapidly with the distance between pipes lower then 2 meters. After the launch of heat pump, heat power of GHX is reduced during the first 20 - 30 days and get steady after that. The obtained results correlate with experimental data. Therefore the proposed mathematical model can be used to design a horizontal GHX with the optimal characteristics, and predict its capability during operation.
The Conduction of Heat through Cryogenic Regenerative Heat Exchangers
Superczynski, W. F.; Green, G. F.
The need for improved regenerative cryocooler efficiency may require the replacement of conventional matrices with ducts. The ducts can not be continuous in the direction of temperature gradient when using conventional materials to prevent unacceptable conduction losses. However, this discontinuity creates a complex geometry to model and determine conduction losses. Chesapeake Cryogenics, Inc. has designed, fabricated and tested an apparatus for measuring the heat conduction through regenerative heat exchangers implementing different matrices. Data is presented for stainless steel photo etched disk, phophorus-bronze embossed ribbon coils and screens made of both stainless steel and phosphorus-bronze. The heat conduction was measured with the regenerators evacuated and pressurized with helium gas. In this test apparatus, helium gas presence increased the heat leak significantly. A description of the test apparatus, instrumentation, experimental methods and data analysis are presented.
A novel compact heat exchanger using gap flow mechanism.
Liang, J S; Zhang, Y; Wang, D Z; Luo, T P; Ren, T Q
A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus. PMID:25725874
Microchannel Heat Exchangers with Carbon Dioxide
Energy Technology Data Exchange (ETDEWEB)
Zhao, Y.; Ohadi, M.M.; Radermacher, R.
The objective of the present study was to determine the performance of CO{sub 2} microchannel evaporators and gas coolers in operational conditions representing those of residential heat pumps. A set of breadboard prototype microchannel evaporators and gas coolers was developed and tested. The refrigerant in the heat exchangers followed a counter cross-flow path with respect to the airflow direction. The test conditions corresponded to the typical operating conditions of residential heat pumps. In addition, a second set of commercial microchannel evaporators and gas coolers was tested for a less comprehensive range of operating conditions. The test results were reduced and a comprehensive data analysis, including comparison with the previous studies in this field, was performed. Capacity and pressure drop of the evaporator and gas cooler for the range of parameters studied were analyzed and are documented in this report. A gas cooler performance prediction model based on non-dimensional parameters was also developed and results are discussed as well. In addition, in the present study, experiments were conducted to evaluate capacities and pressure drops for sub-critical CO{sub 2} flow boiling and transcritical CO{sub 2} gas cooling in microchannel heat exchangers. An extensive review of the literature failed to indicate any previous systematic study in this area, suggesting a lack of fundamental understanding of the phenomena and a lack of comprehensive data that would quantify the performance potential of CO{sub 2} microchannel heat exchangers for the application at hand. All experimental tests were successfully conducted with an energy balance within {+-}3%. The only exceptions to this were experiments at very low saturation temperatures (-23 C), where energy balances were as high as 10%. In the case of evaporators, it was found that a lower saturation temperature (especially when moisture condensation occurs) improves the overall heat transfer coefficient
Heat exchanger life extension via in-situ reconditioning
Holcomb, David E.; Muralidharan, Govindarajan
A method of in-situ reconditioning a heat exchanger includes the steps of: providing an in-service heat exchanger comprising a precipitate-strengthened alloy wherein at least one mechanical property of the heat exchanger is degraded by coarsening of the precipitate, the in-service heat exchanger containing a molten salt working heat exchange fluid; deactivating the heat exchanger from service in-situ; in a solution-annealing step, in-situ heating the heat exchanger and molten salt working heat exchange fluid contained therein to a temperature and for a time period sufficient to dissolve the coarsened precipitate; in a quenching step, flowing the molten salt working heat-exchange fluid through the heat exchanger in-situ to cool the alloy and retain a supersaturated solid solution while preventing formation of large precipitates; and in an aging step, further varying the temperature of the flowing molten salt working heat-exchange fluid to re-precipitate the dissolved precipitate.
Active heat exchange system development for latent heat thermal energy storage
Lefrois, R. T.; Mathur, A. K.
Five tasks to select, design, fabricate, test and evaluate candidate active heat exchanger modules for future applications to solar and conventional utility power plants were discussed. Alternative mechanizations of active heat exchange concepts were analyzed for use with heat of fusion phase change materials (PCMs) in the temperature range of 250 to 350 C. Twenty-six heat exchange concepts were reviewed, and eight were selected for detailed assessment. Two candidates were selected for small-scale experimentation: a coated tube and shell heat exchanger and a direct contact reflux boiler. A dilute eutectic mixture of sodium nitrate and sodium hydroxide was selected as the PCM from over 50 candidate inorganic salt mixtures. Based on a salt screening process, eight major component salts were selected initially for further evaluation. The most attractive major components in the temperature range of 250 to 350 C appeared to be NaNO3, NaNO2, and NaOH. Sketches of the two active heat exchange concepts selected for test are given.
New plates for different types of plate heat exchangers
Fernandes, Carla S.; Dias, Ricardo P.; João M. Maia
The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930's and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950's and initially they were converted dairy models. Brazed plate heat exchange...
Investigation Status of Heat Exchange while Boiling Hydrocarbon Fuel
Directory of Open Access Journals (Sweden)
D. S. Obukhov
Full Text Available The paper contains analysis of heat exchange investigations while boiling hydrocarbon fuel. The obtained data are within the limits of the S.S. Kutateladze dependence proposed in 1939. Heat exchange at non-stationary heat release has not been investigated. The data for hydrocarbon fuel with respect to critical density of heat flow are not available even for stationary conditions.
Automatic evolution of heat exchanger networks with simultaneous heat exchanger design
Energy Technology Data Exchange (ETDEWEB)
Liporace, F.S.; Pessoa, F.L.P.; Queiroz, E.M. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Escola de Quimica. Dept. de Engenharia Quimica]. E-mail: firstname.lastname@example.com; email@example.com
Recently, a new software (AtHENS) that automatically synthesizes a heat exchanger network with minima consumption of utilities was developed. This work deals with the next step, which represents the evolution of the initial network. Hence, new procedures to identify and break loops are incorporated, for which a new algorithm is proposed. Also, a heat exchanger design procedure which uses the available pressure drop to determine the film coefficient on the tube side and shell side is added, providing the utilization of more realistic heat exchangers in the network during its optimization. Results obtained from a case study point to the possibility of equipment design having a strong influence on the network synthesis. (author)
Development of Submersible Corrugated Pipe Sewage Heat Exchanger
Institute of Scientific and Technical Information of China (English)
BAI Li; SHI Yan; TAN Yu-fei
Based on the characteristics of heat transfer for corrugated pipe,a method of calculating and de-sign on the submersible corrugated pipe sewage heat exchanger was put forward theoretically and experimental-ly.The actual movement parameters of air-conditioning system used in this heat exchanger were measured.The experimental result shows that the quantity of heat transfer of the corrugated pipe sewage heat exchanger can satisfy the building's load with the average coefficient of performance 4.55.At the same time.the quantity ot heat transfer of the corrugated pipe sewage heat exchanger was compared with that of the other nonmetallic sewage heat exchangers(i.e.,the plastic-Al pipe sewage heat exchanger and PP-R pipe sewage heat exchanger)experimentally.It is found out that the effect of heat transfer for submersible corrugated pipe sewage heat ex-changer is superior to those of the plastic-Al pipe and the PP-R pipe.The quantity of heat transfer per mile of corrugated pipe sewage heat exchanger is 5.2 times as much as that of the plastic-Al pipe,and it is 8.1 times as much as that of PP-R pipe.
Reliability analysis on a shell and tube heat exchanger
Lingeswara, S.; Omar, R.; Mohd Ghazi, T. I.
A shell and tube heat exchanger reliability was done in this study using past history data from a carbon black manufacturing plant. The heat exchanger reliability study is vital in all related industries as inappropriate maintenance and operation of the heat exchanger will lead to major Process Safety Events (PSE) and loss of production. The overall heat exchanger coefficient/effectiveness (Uo) and Mean Time between Failures (MTBF) were analyzed and calculated. The Aspen and down time data was taken from a typical carbon black shell and tube heat exchanger manufacturing plant. As a result of the Uo calculated and analyzed, it was observed that the Uo declined over a period caused by severe fouling and heat exchanger limitation. This limitation also requires further burn out period which leads to loss of production. The MTBF calculated is 649.35 hours which is very low compared to the standard 6000 hours for the good operation of shell and tube heat exchanger. The guidelines on heat exchanger repair, preventive and predictive maintenance was identified and highlighted for better heat exchanger inspection and repair in the future. The fouling of heat exchanger and the production loss will be continuous if proper heat exchanger operation and repair using standard operating procedure is not followed.
Performance of heat pumps with direct expansion in vertical ground heat exchangers in heating mode
International Nuclear Information System (INIS)
Highlights: • The work focuses on direct expansion ground source heat pumps in heating mode. • The evaporating process of the refrigerant fluid into boreholes is analyzed. • A method to design the direct expansion borehole heat exchangers is presented. • Direct expansion and the common secondary loop heat pumps are compared. • The comparison is carried out in terms of both borehole length and performance. - Abstract: Ground source heat pump systems represent an interesting example of renewable energy technology for heating and cooling of buildings. The connection with the ground is usually done by means of a closed loop where a heat-carrier fluid (pure water or a solution of antifreeze and water) flows and, in heating mode, moves heat from ground to refrigerant fluid of heat pump. A new solution is the direct expansion heat pump. In this case, the heat-carrier fluid inside the ground loop is the same refrigerant fluid of heat pump. This paper focuses on the energy performance of direct expansion ground source heat pump with borehole heat exchangers in heating mode, looking at residential building installations. For this purpose, the evaporating process of the refrigerant fluid inside vertical tubes is investigated in order to analyze the influence of the convective heat transfer coefficient on the global heat transfer with the surrounding ground. Then, an analytical model reported in literature for the design of common borehole heat exchangers has been modified for direct expansion systems. Finally, the direct expansion and common ground source heat pumps have been compared in terms of both total borehole length and thermal performance. Results indicate that the direct expansion system has higher energy performance and requires lower total borehole length compared to the common system. However, when the two systems are compared with the same mean fluid evaporating temperature, the overall length of the ground heat exchanger of the direct expansion heat
Expanded microchannel heat exchanger: design, fabrication and preliminary experimental test
Denkenberger, David C; Pearce, Joshua M; Zhai, John; 10.1177/0957650912442781
This paper first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This paper presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effectiveness. The paper discusses one possible joining method - a new type of laser welding named "forward conduction welding," used to fabricate the prototype. The expanded heat exchanger has the potential to have counter-flow, cross-flow, or parallel-flow configurations, be used for all types of fluids, and be made of polymers, metals, or polymer-ceramic precursors. The cost and ineffectiveness reduction may be an order of magnitude or more, saving a large fraction of primary energy. The measured effectiveness of the prototype with 28 micro...
New counter flow heat exchanger designed for ventilation systems in cold climates
Energy Technology Data Exchange (ETDEWEB)
Kragh, J.; Rose, J.; Nielsen, T.R.; Svendsen, S. [Technical University of Denmark, Lyngby (Denmark). Dept. of Civil Engineering
In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure drop. Preheating the inlet air (outdoor air) to a temperature above zero degrees C before it enters the exchanger is one solution often used to solve the problem, however, this method reduces the energy saving potential significantly. To minimize the energy cost, a more efficient way to solve the freezing problem is therefore desirable. In this paper, the construction and test measurements of a new counter flow heat exchanger designed for cold climates are presented. The developed heat exchanger is capable of continuously defrosting itself without supplementary heating. Other advantages of the developed heat exchanger are low pressure loss, cheap materials, and a simple construction. The disadvantage is that the exchanger is big compared with other heat exchangers. In this paper, the new heat exchanger's efficiency is calculated theoretically and measured experimentally. The experiment shows that the heat exchanger is capable of continuously defrosting itself at outside air temperatures well below the freezing point while still maintaining a very high efficiency. Further analysis and development of a detailed simulation model of a counter flow air-to-air heat exchanger will be described in future articles. (author)
Preliminary Analysis on Heat Removal Capacity of Passive Air-Water Combined Cooling Heat Exchanger Using MARS
Energy Technology Data Exchange (ETDEWEB)
Kim, Seung-Sin; Jeon, Seong-Su; Hong, Soon-Joon [FNC Tech, Yongin (Korea, Republic of); Bae, Sung-Won; Kwon, Tae-Soon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
Current design requirement for working time of PAFS heat exchanger is about 8 hours. Thus, it is not satisfied with the required cooling capability for the long term SBO(Station Black-Out) situation that is required to over 72 hours cooling. Therefore PAFS is needed to change of design for 72 hours cooling. In order to acquirement of long terms cooling using PAFS, heat exchanger tube has to be submerged in water tank for long time. However, water in the tank is evaporated by transferred heat from heat exchanger tubes, so water level is gradually lowered as time goes on. The heat removal capacity of air cooling heat exchanger is core parameter that is used for decision of applicability on passive air-water combined cooling system using PAFS in long term cooling. In this study, the development of MARS input model and plant accident analysis are performed for the prediction of the heat removal capacity of air cooling heat exchanger. From analysis result, it is known that inflow air velocity is the decisive factor of the heat removal capacity and predicted air velocity is lower than required air velocity. But present heat transfer model and predicted air velocity have uncertainty. So, if changed design of PAFS that has over 4.6 kW heat removal capacity in each tube, this type heat exchanger can be applied to long term cooling of the nuclear power plant.
Heat transfer enhancement utilizing chaotic advection in coiled tube heat exchangers
International Nuclear Information System (INIS)
The present study introduced a novel chaotic coil heat exchanger utilizing chaotic advection to enhance heat transfer at low Reynolds numbers. Using Lagrangian tracing of fluid particles and their sensitivity to the initial condition and fluid element calculations, it was shown that mixing was significantly increased due to the chaotic advection. Heat transfer performance in the coil and chaotic configuration was visualized by isotherms contours of temperature in different cross-sections. In order to evaluate the hydraulic-thermal performance of heat exchangers, Nusselt numbers and friction factor were calculated and comparison was made between the two configurations. Numerical calculations revealed that the chaotic coil configuration displayed heat transfer enhancement of 4–26% relative to the fully developed Nusselt numbers in the regular coil with only 5–8% change in the pressure drop. - Highlights: • A novel chaotic coil heat exchanger is introduced in this study. • It is shown that mixing is increased significantly due to the altered chaotic advection mechanism. • By increasing the Reynolds number, results show impressive enhancement in chaotic heat exchanger performance. • Reorientation in chaotic flow leads to higher pressure loss than that in the normal helical coil
Heat Exchanger Anchors for Thermo-active Tunnels
Mimouni, Thomas; Dupray, Fabrice; Minon, Sophie; LALOUI, Lyesse
Shallow geothermal power represents an important energy resource for the heating and cooling of the buildings. Due to relatively low temperature levels encountered at shallow depths in the soil, between 10°C and 20°C, heat pumps are required to process the extracted heat, forming the so called ground source heat pump system. Different types of heat exchangers with the ground were developed in order to optimize the heat exchanges, from simple geothermal loops grouted in boreholes reaching dept...
Directory of Open Access Journals (Sweden)
Full Text Available This paper presents the findings obtained by modeling a Double Pipe Heat Exchanger (DPHE equipped with repeated ribs from the inside for artificial roughing. An analytical procedure was developed to analyze the thermal and hydraulic performance of the DPHE with and without ribbing. The procedure was verified by comparing with experimental reported results and they are in good agreement. Several parameters were investigated in this study including the effect of ribs pitch to height ratios, P/e= 5, 10, 15, and 20, and ribs to hydraulic diameter ratios, e/Dh= 0.0595, 0.0765, and 0.107. These parameters were studied at various operating Reynolds number ranging from 2500 to 150000. Different installation configurations were investigated, too. An enhan-cement of 4 times in the heat transfer in terms of Stanton number was achieved at the expense of 38 times increase of pressure drop across the flow in terms of friction facto values.
Simultaneous derivation of clothing-specific heat exchange coefficients.
Kenney, W L; Mikita, D J; Havenith, G; Puhl, S M; Crosby, P
Clothing adds resistance to heat exchange between the wearer and the environment. If clothing-specific heat exchange coefficients are known, a combined rational/empirical approach can be used to describe thermal exchange between clothed humans and the environment. However, during exercise these coefficients--typically calculated using thermal manikins--change, primarily due to wetting of the fabric during intense sweating and body movement. A procedure is described that allows for the simultaneous determination of both total insulation (IT) and resistance to water vapor permeation (Re) on exercising clothed subjects without the need to directly measure skin water vapor pressure or continuously weigh the subjects. Two tests are performed by each subject in each clothing ensemble. In one test, ambient water vapor pressure (Pa) is systematically increased in stepwise fashion while dry-bulb temperature (Tdb) is held constant; in the second test protocol Pa is held constant while Tdb is increased. Heat exchange data are collected at the time at which core temperature is forced out of equilibrium by the environment (according to the assumption that heat production is balanced by heat loss immediately prior to this critical environmental limit). Previous studies using similar approaches have typically estimated IT a priori and used this value in the subsequent derivation of Re for each clothing ensemble or condition tested. In the proposed method, IT and Re are derived from the solution of two simultaneous equations based on heat balance data from both tests. This paper describes and critiques this methodology via an error analysis, and compares the coefficients obtained with those from similar trials using other physiological and nonphysiological approaches. PMID:8450734
Simulation Studies on A Cross Flow Plate Fin Heat Exchanger
Directory of Open Access Journals (Sweden)
M. Thirumarimurugan
Full Text Available Compact heat exchangers which were initially developed for the aerospace industries in the1940s have been considerably improved in the past few years. The main reasons for the goodperformance of compact heat exchangers are their special design which includes turbulent which inturn use high heat transfer coefficient and resists fouling, and maximum temperature driving forcebetween the hot and cold fluids. Numerous types use special enhancement techniques to achieve therequired heat transfer in smaller plot areas and, in many cases, less initial investment. One such type ofcompact heat exchanger is the Plate-fin heat exchanger. The complexity of compact heat exchangerdesign equations results from the exchangers unique ability to transfer heat between multiple processstreams and a wide array of possible flow configurations. This paper presents the performanceevaluation of cross flow plate fin heat exchanger with several different Gas-Liquid systems.Experimental results such as exchanger effectiveness, overall heat transfer coefficients were calculatedfor the flow systems of Cross flow Heat Exchangers. A steady state model for the outlet temperature ofboth the cold and hot fluid and overall heat transfer coefficient of a plate-fin cross flow heat exchangerwas developed and simulated using MATLAB, which was verified with the experiments conducted.
Design of heat exchanger for heating UF6 feed in nuclear fuel element plant
International Nuclear Information System (INIS)
The process of conversion of UF6 to UO2 through Integrated Dry Route (IDR) is done in a rotary kiln reactor. There are two stages of initial treatment / conditioning before inserting the UF6 in to the reactor: changing UF6 solid into the gas phase at a temperature of 60°C in an evaporator, and then, raising the temperature of UF6 gas from 60°C to 290°C in a Heat Exchanger (HE). Therefore it is necessary to design a HE for heating UF6 gas by determination / calculation of HE specifications as a heater. The steps activities of determining the specifications of HE in the Following sequence: determining the value of the heat load Q, determining the approximate dimensions of the Heat Exchanger, determining the dimensions / specifications corrected Heat Exchanger, HE pressure drop calculation. The result of this design specification is a type of hairpin double pipe HE with a length of 12 ft, 2 x 1 ¼. IPS. Pipe material is Inconel (alloy -600) that is resistant to UF6, HF, and Steam. Annulus material is carbon steel. Pressure drop in annulus is 0.0004 psi, and in inner pipe is 0.042 psi. Heat Exchanger with specs like this can function as UF6 gas heater so that the temperature be 290°C. (author)
Optimization of the Single Staggered Wire and Tube Heat Exchanger
Arsana I Made; Susianto; Budhikarjono Kusno; Altway Ali
Wire and tube heat exchanger consists of a coiled tube, and wire is welded on the two sides of it in normal direction of the tube. Generally,wire and tube heat exchanger uses inline wire arrangement between the two sides, whereas in this study, it used staggered wire arrangement that reduces the restriction of convection heat transfer. This study performed the optimization of single staggered wire and tube heat exchanger to increase the capacity and reduce the mass of the heat exchanger. Opti...
Geothermal direct contact heat exchange. Final report
Energy Technology Data Exchange (ETDEWEB)
Sims, A.V.
A glass direct contact heat exchange column was operated in the laboratory. The column was operated at atmospheric pressure using hot water and normal hexane. Column internals testing included an empty column, sieve trays, disk-and-doughnut trays, and two types of packing. Operation was very smooth in all cases and the minimum temperature approaches varied from less than 1/sup 0/C for packing to 13/sup 0/C for the empty column. High heat transfer rates were obtained in all cases, however, columns should be sized on the basis of liquid and vapor traffic. The solubilities of hydrocarbons were determined for normal hexane, pentane and butane in water and sodium chloride and calcium chloride brines at various temperatures. The values seem to be internally consistent and salt content was found to depress hydrocarbon solubility. Laboratory stripping tests showed that gas stripping can be used to remove hydrocarbon from reject hot water from the direct contact heat exchange column. Although the gas volumes required are small, stripping gas requirements cannot be accurately predicted without testing. A computer program was used to study the effect of operating variables on the thermodynamic cycle efficiencies. Optimum efficiencies for the moderate brine conditions studied were obtained with isopentane as working fluid and relatively low operating pressure. A preliminary design for a 50 MWe plant was prepared and plant capital cost and operating cost were estimated. These costs were combined with previously developed brine production and power transmission costs to provide an estimate of the cost of delivered power for a geothermal field at Heber, California. A pilot plant program is described that would be suitable for continuing the investigation of the direct contact process in the field. The program includes a suggested schedule and the estimated cost.
Entropy resistance minimization: An alternative method for heat exchanger analyses
International Nuclear Information System (INIS)
In this paper, the concept of entropy resistance is proposed based on the entropy generation analyses of heat transfer processes. It is shown that smaller entropy resistance leads to larger heat transfer rate with fixed thermodynamic force difference and smaller thermodynamic force difference with fixed heat transfer rate, respectively. For the discussed two-stream heat exchangers in which the heat transfer rates are not given and the three-stream heat exchanger with prescribed heat capacity flow rates and inlet temperatures of the streams, smaller entropy resistance leads to larger heat transfer rate. For the two-stream heat exchangers with fixed heat transfer rate, smaller entropy resistance leads to larger effectiveness. Furthermore, it is shown that smaller values of the concepts of entropy generation numbers and modified entropy generation number do not always correspond to better performance of the discussed heat exchangers. - Highlights: • The concept of entropy resistance is defined for heat exchangers. • The concepts based on entropy generation are used to analyze heat exchangers. • Smaller entropy resistance leads to better performance of heat exchangers. • The applicability of entropy generation minimization is conditional
40 CFR 63.1435 - Heat exchanger provisions.
...) When the HON heat exchange system requirements in § 63.104 refer to Table 4 of 40 CFR part 63, subpart... 40 Protection of Environment 11 2010-07-01 2010-07-01 true Heat exchanger provisions. 63.1435... Standards for Hazardous Air Pollutant Emissions for Polyether Polyols Production § 63.1435 Heat...
Heat transfer entropy resistance for the analyses of two-stream heat exchangers and two-stream heat exchanger networks
International Nuclear Information System (INIS)
The entropy generation minimization method is often used to analyze heat transfer processes from the thermodynamic viewpoint. In this paper, we analyze common heat transfer processes with the concept of entropy generation, and propose the concept of heat transfer entropy resistance. It is found that smaller heat transfer entropy resistance leads to smaller equivalent thermodynamic force difference with prescribed heat transfer rate and larger heat transfer rate with prescribed equivalent thermodynamic force difference. With the concept of heat transfer entropy resistance, the performance of two-stream heat exchangers (THEs) and two-stream heat exchanger networks (THENs) is analyzed. For the cases discussed in this paper, it is found that smaller heat transfer entropy resistance always leads to better heat transfer performance for THEs and THENs, while smaller values of the entropy generation, entropy generation numbers and revised entropy generation number do not always. -- Highlights: • The concept of entropy resistance is defined. • The minimum entropy resistance principle is developed. • Smaller entropy resistance leads to better heat transfer
Research on ground heat exchanger of Ground Source Heat Pump technique
Institute of Scientific and Technical Information of China (English)
LIU Dong-sheng; SUN You-hong; GAO Ke; WU Xiao-hang
Ground Source Heat Pump technique and its operating principle are described in this paper. Ground heat exchanger is the key technique of ground source heat pump and its pattems are discussed. Software is helpful to design ground heat exchanger. A project of Chinese Ground Source Heat Pump is introduced and its market is more and more extensive.
Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles
Kılıç, Bayram; İpek, Osman
In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.
Magnetic Heat Transfer Enhancements on Fin-Tube Heat Exchangers
Institute of Scientific and Technical Information of China (English)
Yan SU; C.T. HSU
通过DNS方法解耦合的三维非稳态流动和固流体能量方程组,本文研究了两平行磁质平板和圆管所组成的肋片式圆管换热器单元与震荡流体间的传热过程.对不同的磁场频率和振幅的三维动态流热场的模拟结果表明增强磁场频率和振幅能很有效地增加周期平均传热强度达到强化传热的目的.%Two narrowly-gapped magnetic parallel plates embedding a circular disk was considered as a unit-cell to represent the fin-tube heat exchanger where heat from a circular tube was dissipated by a series of parallel equally-spaced thin plates in normal to the tube. The unsteady 3-D continuity,Navier-Stokes and energy equations for fluids and solids describing the convective heat transfer for the unit-cell geometry were solved numerically with DNS method. The present study aims on using oscillating flows and magnetic fields to enhance the heat transfer for various amplitudes and frequencies of the magnetic field. Results from cycle-averaged heat fluxes from the cylinder wall show that the increase in magnetic amplitude and frequency will greatly enhance the heat transfer. The effects of the oscillating magnetic field were discussed and the three dimensional flow and temperature fields were also presented.
Heat exchangers and the performance of heat pumps - Analysis of a heat pump database
International Nuclear Information System (INIS)
Heat pumping is a highly energy-efficient technology that could help reduce energy and environmental problems. The efficiency of a heat pump greatly depends on the individual and integral performance of the components inside. In this study, heat pump performance is investigated with a special focus on heat exchangers. Experimental data obtained from comprehensive heat pump measurements performed at the Austrian Institute of Technology (AIT) were analyzed with the help of thermodynamic models developed for this purpose. The analysis shows that the performance of heat exchangers varies widely resulting in substantial COP differences among the heat pumps. The models and methodology developed in this study are found capable of extracting useful information from measurement data quickly and accurately and could be useful for the industry. - Research highlights: → A heat pump database has been analyzed focussing on the influences of heat exchangers on COP. → It was shown that an empirical equation could excellently correlate experimental COP data with relevant parameters. → It was found that heat exchanger design alone caused 15-20% difference in COP.
Vaibhav Madane; Meeta Vedpathak
This project focuses on Earth Air Heat Exchanger which is reducing energy consumption in a building. The air is passing through the buried tubes and heat exchange takes place between air and surrounding soil. This equipment helps to reduce energy consumption of an air conditioning unit. This project analyses the thermal performance of earth air heat exchanger by using computational fluid dynamics modeling. The model is validated against experimental observations and investigations...
High temperature heat exchanger studies for applications to gas turbines
Min, June Kee; Jeong, Ji Hwan; Ha, Man Yeong; Kim, Kui Soon
Growing demand for environmentally friendly aero gas-turbine engines with lower emissions and improved specific fuel consumption can be met by incorporating heat exchangers into gas turbines. Relevant researches in such areas as the design of a heat exchanger matrix, materials selection, manufacturing technology, and optimization by a variety of researchers have been reviewed in this paper. Based on results reported in previous studies, potential heat exchanger designs for an aero gas turbine recuperator, intercooler, and cooling-air cooler are suggested.
Simultaneous synthesis of work exchange networks with heat integration
Onishi, Viviani C.; Ravagnani, Mauro A.S.S.; Caballero Suárez, José Antonio
The optimal integration of work and its interaction with heat can represent large energy savings in industrial plants. This paper introduces a new optimization model for the simultaneous synthesis of work exchange networks (WENs), with heat integration for the optimal pressure recovery of process gaseous streams. The proposed approach for the WEN synthesis is analogous to the well-known problem of synthesis of heat exchanger networks (HENs). Thus, there is work exchange between high-pressure ...
Heat exchanger and water tank arrangement for passive cooling system
Energy Technology Data Exchange (ETDEWEB)
Gillett, James E. (Greensburg, PA); Johnson, F. Thomas (Baldwin Boro, PA); Orr, Richard S. (Pittsburgh, PA); Schulz, Terry L. (Murrysville Boro, PA)
A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tubesheets mounted to the tank connections so that the tubesheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tubesheets on a square pitch and then on a rectangular pitch therebetween. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight.
Two-phase Flow Distribution in Heat Exchanger Manifolds
Vist, Sivert
The current study has investigated two-phase refrigerant flow distribution in heat exchange manifolds. Experimental data have been acquired in a heat exchanger test rig specially made for measurement of mass flow rate and gas and liquid distribution in the manifolds of compact heat exchangers. Twelve different manifold designs were used in the experiments, and CO2 and HFC-134a were used as refrigerants.
Performance of multiple mini-tube heat exchangers as an internal heat exchanger of a vapor-injection cycle heat pump
Jang, Jin Yong; Jeong, Ji Hwan
A multiple mini-tube (MMT) heat exchanger was considered as an internal heat exchanger of vapor-injection cycle heat pump. Heat transfer and pressure drop in multiple mini-tube heat exchangers were numerically and experimentally investigated. Results show that the best performance of the MMT heat exchanger can be obtained when the intermediate-pressure two-phase refrigerant is supplied to the shell-side and this refrigerant reaches a saturated vapor state at the exit of the heat exchanger.
Polymer spiral film gas-liquid heat exchanger for waste heat recovery in exhaust gases
Breton, Antoine
In this master thesis report the development of an innovative spiral heat exchanger based on polymer materials is described. Building prototypes, erection of a test bench and firsts tests of the heat exchanger are presented. The heat exchanger prototype survived all tests especially several days in contact with aggressive gases. A facility integrating a Diesel exhaust gases production has been developed to test this heat exchanger design. Performance results obtained during the tes...
Inservice inspection of PFR secondary heat exchangers
International Nuclear Information System (INIS)
The author describes the current state of development to meet inservice inspection requirements of secondary heat exchangers of a prototype fast reactor: detection of defects in both the bore and outer surface of the tubes (pitting and cracking in the bore surface and fretting and thinning on the outer), full inspection of bends and straight portions, examination of the tube plate and of the tube/tube plate weld region. He reports the development of an eddy current probe for the in-service inspection (ISI) of the stainless steel tubing in the super-heater and re-heater, describes the influence of sodium concentration on eddy current inspection, and briefly evokes the detection of defects in bends. He describes the eddy current inspection of the evaporator tube bores, the wall thickness measurement in evaporator tubes. Then, he reports the in-service inspection of tube plates: tube bore examination, volumetric examination. He briefly discusses the obtained results
FASTEF Heat exchanger tube rupture CFD simulation
Energy Technology Data Exchange (ETDEWEB)
Moreau, V., E-mail: firstname.lastname@example.com [CRS4, Centre for Advanced Studies, Research and Development in Sardinia, Polaris, Edificio 1, 09010 Pula, CA (Italy)
The aim of this technical note is to present CFD simulations of a tube rupture incidental scenario in a Primary Heat eXchanger (PHX)/Primary Pump (PP) assembly for two design variants of the FAst-Spectrum Transmutation Experimental Facility FASTEF ongoing design, in the framework of the FP7 Central Design Team (CDT) European project. The simulation domain reproduces with some simplification the entire primary coolant loop. The objective is to understand whether it is necessary take some counter-measures to avoid the ingress of steam in the cold plenum. The simulation has been performed on two successive updates of the design and of the nominal operation. The simulations show a good resistance to steam ingress, under the condition that provision is made to avoid an excessive accumulation of steam at the top of the PHX/PP assembly casing.
Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating
Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor)
A multi-layer antimicrobial hydrophilic coating is applied to a substrate of anodized aluminum, although other materials may form the substrate. A silver layer is sputtered onto a thoroughly clean anodized surface of the aluminum to about 400 nm thickness. A layer of crosslinked, silicon-based macromolecular structure about 10 nm thickness overlies the silver layer, and the outermost surface of the layer of crosslinked, silicon-based macromolecular structure is hydroxide terminated to produce a hydrophilic surface with a water drop contact angle of less than 10.degree.. The coated substrate may be one of multiple fins in a condensing heat exchanger for use in the microgravity of space, which has narrow channels defined between angled fins such that the surface tension of condensed water moves water by capillary flow to a central location where it is pumped to storage. The antimicrobial coating prevents obstruction of the capillary passages.
Direct contact droplet heat exchangers for thermal management in space
Bruckner, A. P.; Hertzberg, A.
A liquid droplet heat exchanger for space applications is described which transfers heat between a gas and a liquid metal dispersed into droplets. The ability of the droplet heat exchanger to transfer heat between two media in direct contact over a wide temperature range circumvents many of the material limitations of conventional tube-type heat exchangers and does away with complicated plumbing systems and their tendency toward single point failure. Droplet heat exchangers offer large surface to volume ratios in a compact geometry, very low gas pressure drop, and high effectiveness. The application of the droplet heat exchanger in a high temperature Brayton cycle is discussed to illustrate its performance and operational characteristics.
Overhaul of the heat exchanger in JRR-3
International Nuclear Information System (INIS)
In JRR-3, heat exchangers are installed in the cooling system equipment to remove the heat generated in the nuclear reactor, For the heat exchangers, overhaul inspection based on the JRR-3 reactor facility maintenance plan, as well as the inspection and maintenance based on reactor facility security provisions and JRR-3 operation guidelines are systematically conducted. Considering the results of overhaul inspection, the second overhaul inspection was applied to the primary coolant heat exchanger. The thinning of heat transfer tubes is within judgment standards with little effects of aging, which verified their soundness. From the fact that the effects of corrosion have been confirmed on the inside of the water chamber, repair work through overlay welding or the like is planned in the next overhaul. As for heavy water heat exchanger and the spent fuel pool water heat exchanger, it is planned to conduct the second overhaul inspection in FY2013 to confirm their soundness. (A.O.)
Thermal energy storage heat exchanger: Molten salt heat exchanger design for utility power plants
Ferarra, A.; Yenetchi, G.; Haslett, R.; Kosson, R.
The use of thermal energy storage (TES) in the latent heat of molten salts as a means of conserving fossil fuels and lowering the cost of electric power was evaluated. Public utility systems provided electric power on demand. This demand is generally maximum during late weekday afternoons, with considerably lower overnight and weekend loads. Typically, the average demand is only 60% to 80% of peak load. As peak load increases, the present practice is to purchase power from other grid facilities or to bring older less efficient fossil-fuel plants on line which increase the cost of electric power. The widespread use of oil-fired boilers, gas turbine and diesel equipment to meet peaking loads depletes our oil-based energy resources. Heat exchangers utilizing molten salts can be used to level the energy consumption curve. The study begins with a demand analysis and the consideration of several existing modern fossil-fuel and nuclear power plants for use as models. Salts are evaluated for thermodynamic, economic, corrosive, and safety characteristics. Heat exchanger concepts are explored and heat exchanger designs are conceived. Finally, the economics of TES conversions in existing plants and new construction is analyzed. The study concluded that TES is feasible in electric power generation. Substantial data are presented for TES design, and reference material for further investigation of techniques is included.
Thermal Propulsion Capture System Heat Exchanger Design
Richard, Evan M.
One of the biggest challenges of manned spaceflight beyond low earth orbit and the moon is harmful radiation that astronauts would be exposed to on their long journey to Mars and further destinations. Using nuclear energy has the potential to be a more effective means of propulsion compared to traditional chemical engines (higher specific impulse). An upper stage nuclear engine would allow astronauts to reach their destination faster and more fuel efficiently. Testing these engines poses engineering challenges due to the need to totally capture the engine exhaust. The Thermal Propulsion Capture System is a concept for cost effectively and safely testing Nuclear Thermal Engines. Nominally, hydrogen exhausted from the engine is not radioactive, but is treated as such in case of fuel element failure. The Thermal Propulsion Capture System involves injecting liquid oxygen to convert the hydrogen exhaust into steam. The steam is then cooled and condensed into liquid water to allow for storage. The Thermal Propulsion Capture System concept for ground testing of a nuclear powered engine involves capturing the engine exhaust to be cooled and condensed before being stored. The hydrogen exhaust is injected with liquid oxygen and burned to form steam. That steam must be cooled to saturation temperatures before being condensed into liquid water. A crossflow heat exchanger using water as a working fluid will be designed to accomplish this goal. Design a cross flow heat exchanger for the Thermal Propulsion Capture System testing which: Eliminates the need for water injection cooling, Cools steam from 5800 F to saturation temperature, and Is efficient and minimizes water requirement.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Energy Technology Data Exchange (ETDEWEB)
Koplow, Jeffrey P.
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Liquid-Liquid Heat Exchanger With Zero Interpath Leakage Project
National Aeronautics and Space Administration — Future manned spacecraft will require thermal management systems that effectively and safely control the temperature in inhabited modules. Interface heat exchangers...
Experimental heat exchanger performance in a thermoacoustic prime mover
Castro, Nelson C.
This thesis investigates the experimental heat exchanger performance in a neon filled thermoacoustic prime mover. The experimental approach is to measure the waveform and spectrum of the acoustic oscillations, as well as the relevant temperatures for heat exchangers of 0.257, 0.569, and 0.82 cm in length. A temperature gradient is established across the stack by submerging the cold heat exchanger and cold end tube in liquid nitrogen and keeping the hot heat exchanger and hot end tube at ambie...
Fouling corrosion in aluminum heat exchangers
Directory of Open Access Journals (Sweden)
Su Jingxin
Full Text Available Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum coupons covered with a layer of artificial fouling in a humid atmosphere by their weight loss, Tafel plots, electrochemical impedance spectroscopy (EIS, and scanning electron microscope (SEM observations. The results reveal that chloride is one of the major elements found in the fouling which damages the passive film and initiates corrosion. The galvanic corrosion between the metal and the adjacent carbon particles accelerates the corrosive process. Furthermore, the black carbon favors the moisture uptake, and gives the dissolved oxygen greater chance to migrate through the fouling layer and form a continuous diffusive path. The corrosion rate decreasing over time is conformed to electrochemistry measurements and can be verified by Faraday's law. The EIS results indicate that the mechanism of corrosion can be interpreted by the pitting corrosion evolution mechanism, and that pitting was observed on the coupons by SEM after corrosive exposure.
Optimization for entransy dissipation minimization in heat exchanger
Institute of Scientific and Technical Information of China (English)
XIA ShaoJun; CHEN LinGen; SUN FengRui
A common of two-fluid flow heat exchanger, in which the heat transfer between high-and low-temperature sides obeys Newton's law [q∝△(T)], is studied in this paper. By taking entransy dissipation minimization as optimization objective, the optimum parameter distributions in the heat ex-changer are derived by using optimal control theory under the condition of fixed heat load. The condition corresponding to the minimum entransy dissipation is that corresponding to a constant heat flux density. Three kinds of heat exchangers, including parallel flow, condensing flow and counter-flow, are considered, and the results show that only the counter-flow heat exchanger can realize the entransy dissipation minimization in the heat transfer process. The obtained results for entransy dissipation minimization are also compared with those obtained for entropy generation minimization by numerical examples.
Measurement of flow field and local heat transfer distribution on a scraped heat exchanger crystalliser surface
Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Witkamp, Geert-Jan
In a cylindrical scraped heat exchanger crystallizer geometry the flow field influence on the local heat transfer distribution on an evenly cooled scraped heat exchanger surface has been studied by direct measurements of the heat exchanger surface temperature and the fluid velocity field inside the crystallizer. Liquid Crystal Thermometry revealed that the local heat transfer is higher in the middle area of the scraped surface. Stereoscopic PIV measurements demonstrated that the secondary flo...
Online performance assessment of heat exchanger using artificial neural networks
Directory of Open Access Journals (Sweden)
C. Ahilan, S. Kumanan, N. Sivakumaran
Full Text Available Heat exchanger is a device in which heat is transferred from one medium to another across a solid surface. The performance of heat exchanger deteriorates with time due to fouling on the heat transfer surface. It is necessary to assess periodically the heat exchanger performance, in order to maintain at high efficiency level. Industries follow adopted practices to monitor but it is limited to some degree. Online monitoring has an advantage to understand and improve the heat exchanger performance. In this paper, online performance monitoring system for shell and tube heat exchanger is developed using artificial neural networks (ANNs. Experiments are conducted based on full factorial design of experiments to develop a model using the parameters such as temperatures and flow rates. ANN model for overall heat transfer coefficient of a design/ clean heat exchanger system is developed using a feed forward back propagation neural network and trained. The developed model is validated and tested by comparing the results with the experimental results. This model is used to assess the performance of heat exchanger with the real/fouled system. The performance degradation is expressed using fouling factor (FF, which is derived from the overall heat transfer coefficient of design system and real system. It supports the system to improve the performance by asset utilization, energy efficient and cost reduction interms of production loss.
Experimental performance studies of a plate heat exchanger
Plath, Darren R.
A plate and frame heat exchanger experimental test stand was developed. Using this test stand a performance analysis was conducted. The analysis consisted of evaluating the performance of the heat exchanger at varying flow rates and inlet temperatures, to develop an effectiveness-NTU and Log Mean Temperature Difference relationships, under steady state operation. The measured heat rates were compared to the heat rates provided by the manufacturer and good/bad agreement was found. Standard ope...
Simulation Studies on A Cross Flow Plate Fin Heat Exchanger
M. Thirumarimurugan; T Kannadasan; E. Ramasamy
Compact heat exchangers which were initially developed for the aerospace industries in the1940s have been considerably improved in the past few years. The main reasons for the goodperformance of compact heat exchangers are their special design which includes turbulent which inturn use high heat transfer coefficient and resists fouling, and maximum temperature driving forcebetween the hot and cold fluids. Numerous types use special enhancement techniques to achieve therequired heat transfer in...
Combined Steady-State and Dynamic Heat Exchanger Experiment
Luyben, William L.; Tuzla, Kemal; Bader, Paul N.
This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…
Principle of uniformity of temperature difference field in heat exchanger
Institute of Scientific and Technical Information of China (English)
过增元; 李志信; 周森泉; 熊大曦
A principle of uniformity of temperature difference field (TDF) in heat exchangers is advanced.It states that the more uniform the temperature difference field,the higher the effectiveness of heat exchanger for a given NTU and C,.Analytical and numerical results on the uniformity of TDF and effectiveness of thirteen types of heat exchangers show the validity of the uniformity principle.Its further verification is given by the asymptotical solution of TDF in terms of a recurrence formula of heat transfer area distribution.The analyses of entropy generation caused by heat transfer indicate that the uniformity principle is based on the second law of thermodynamics.Two ways,redistributing heat transfer areas and varying the connection between tubes,are presented for the improvement of the uniformity of TDF and the consequent increase of effectiveness for crossflow heat exchangers.
A Modified Entropy Generation Number for Heat Exchangers
Institute of Scientific and Technical Information of China (English)
This paper demonstrates the difference between the entropy generation number method proposed by Bejian and the method of entropy generation per unit amount of heat transferred in analyzing the ther-modynamic performance of heat exchangers,points out the reason for leading to the above difference.A modified entropy generation number for evaluating the irreversibility of heat exchangers is proposed which is in consistent with the entropy generation per unit amount of heat transferred in entropy generation analysis.The entropy generated by friction is also investigated.Results show that when the entropy generated by friction in heat exchangers in taken into account,there is a minimum total entropy generation number while the NTU and the ratio of heat capacity rates vary.The existence of this minimum is the prerequisite of heat exchanger optimization.
Design Calculation of Heat Exchanger of Reflooding Test
Institute of Scientific and Technical Information of China (English)
DUAN; Ming-hui; LI; Xiang; LI; Wei-qing
The heat exchanger is very important to the major loop of the reflooding test.It can cool the fluid in the loop,so that the fluid temperature can agree with the requirements of the major pump and the preheater.Herein,an evaporative exchanger with U-shape tubes is adopted.The heat transfer calculation
Cyclic high temperature heat storage using borehole heat exchangers
Boockmeyer, Anke; Delfs, Jens-Olaf; Bauer, Sebastian
The transition of the German energy supply towards mainly renewable energy sources like wind or solar power, termed "Energiewende", makes energy storage a requirement in order to compensate their fluctuating production and to ensure a reliable energy and power supply. One option is to store heat in the subsurface using borehole heat exchangers (BHEs). Efficiency of thermal storage is increasing with increasing temperatures, as heat at high temperatures is more easily injected and extracted than at temperatures at ambient levels. This work aims at quantifying achievable storage capacities, storage cycle times, injection and extraction rates as well as thermal and hydraulic effects induced in the subsurface for a BHE storage site in the shallow subsurface. To achieve these aims, simulation of these highly dynamic storage sites is performed. A detailed, high-resolution numerical simulation model was developed, that accounts for all BHE components in geometrical detail and incorporates the governing processes. This model was verified using high quality experimental data and is shown to achieve accurate simulation results with excellent fit to the available experimental data, but also leads to large computational times due to the large numerical meshes required for discretizing the highly transient effects. An approximate numerical model for each type of BHE (single U, double U and coaxial) that reduces the number of elements and the simulation time significantly was therefore developed for use in larger scale simulations. The approximate numerical model still includes all BHE components and represents the temporal and spatial temperature distribution with a deviation of less than 2% from the fully discretized model. Simulation times are reduced by a factor of ~10 for single U-tube BHEs, ~20 for double U-tube BHEs and ~150 for coaxial BHEs. This model is then used to investigate achievable storage capacity, injection and extraction rates as well as induced effects for
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, H. J. H.; Geld, van der, C.W.M.
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall condensation and fog formation are considered in some detail. Separate attention is paid to the heat transfer and condensation of pure steam in the heat exchanger. Finally, the experiments performed...
The heat exchanger of small pellet boiler for phytomass
Mičieta, Jozef; Lenhard, Richard; Jandačka, Jozef
Combustion of pellets from plant biomass (phytomass) causes various troubles. Main problem is slagging ash because of low melting temperature of ash from phytomass. This problem is possible to solve either improving energetic properties of phytomass by additives or modification of boiler construction. A small-scale boiler for phytomass is different in construction of heat exchanger and furnace mainly. We solve major problem - slagging ash, by decreasing combustion temperature via redesign of pellet burner and boiler body. Consequence of lower combustion temperature is also lower temperature gradient of combustion gas. It means that is necessary to design larger heat exchanging surface. We plane to use underfed burner, so we would utilize circle symmetry heat exchanger. Paper deals design of heat exchanger construction with help of CFD simulation. Our purpose is to keep uniform water flux and combustion gas flux in heat exchanger without zone of local overheating and excess cooling.
A concept of PWR using plate and shell heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Freire, Luciano Ondir; Andrade, Delvonei Alves de, E-mail: firstname.lastname@example.com, E-mail: email@example.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
In previous work it was verified the physical possibility of using plate and shell heat exchangers for steam generation in a PWR for merchant ships. This work studies the possibility of using GESMEX commercial of the shelf plate and shell heat exchanger of series XPS. It was found it is feasible for this type of heat exchanger to meet operational and accidental requirements for steam generation in PWR. Additionally, it is proposed an arrangement of such heat exchangers inside the reactor pressure vessel. Such arrangement may avoid ANSI/ANS51.1 nuclear class I requirements on those heat exchangers because they are contained in the reactor coolant pressure barrier and play no role in accidental scenarios. Additionally, those plates work under compression, preventing the risk of rupture. Being considered non-nuclear safety, having a modular architecture and working under compression may turn such architectural choice a must to meet safety objectives with improved economics. (author)
A concept of PWR using plate and shell heat exchangers
International Nuclear Information System (INIS)
In previous work it was verified the physical possibility of using plate and shell heat exchangers for steam generation in a PWR for merchant ships. This work studies the possibility of using GESMEX commercial of the shelf plate and shell heat exchanger of series XPS. It was found it is feasible for this type of heat exchanger to meet operational and accidental requirements for steam generation in PWR. Additionally, it is proposed an arrangement of such heat exchangers inside the reactor pressure vessel. Such arrangement may avoid ANSI/ANS51.1 nuclear class I requirements on those heat exchangers because they are contained in the reactor coolant pressure barrier and play no role in accidental scenarios. Additionally, those plates work under compression, preventing the risk of rupture. Being considered non-nuclear safety, having a modular architecture and working under compression may turn such architectural choice a must to meet safety objectives with improved economics. (author)
Design of Heat Exchanger for Ericsson-Brayton Piston Engine
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Peter Durcansky
Full Text Available Combined power generation or cogeneration is a highly effective technology that produces heat and electricity in one device more efficiently than separate production. Overall effectiveness is growing by use of combined technologies of energy extraction, taking heat from flue gases and coolants of machines. Another problem is the dependence of such devices on fossil fuels as fuel. For the combustion turbine is mostly used as fuel natural gas, kerosene and as fuel for heating power plants is mostly used coal. It is therefore necessary to seek for compensation today, which confirms the assumption in the future. At first glance, the obvious efforts are to restrict the use of largely oil and change the type of energy used in transport. Another significant change is the increase in renewable energy—energy that is produced from renewable sources. Among machines gaining energy by unconventional way belong mainly the steam engine, Stirling engine, and Ericsson engine. In these machines, the energy is obtained by external combustion and engine performs work in a medium that receives and transmits energy from combustion or flue gases indirectly. The paper deals with the principle of hot-air engines, and their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element.
Modeling of Heat Exchange with Developed Nucleate Boiling on Tenons
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A. V. Оvsiannik
Full Text Available The paper proposes a thermal and physical model for heat exchange processes with developed nucleate boiling on the developed surfaces (tenons with various contours of heat transfer surface. Dependences for calculating convective heat exchange factor have been obtained on the basis of modeling representation. Investigations have shown that an intensity of convective heat exchange does not depend on tenon profile when boiling takes place on the tenons. The intensity is determined by operating conditions, thermal and physical properties of liquid, internal characteristics of boiling processes and geometrical characteristics of a tenon.
Valiulin, S.; Shabarov, V.
A calculation procedure for gas-dynamic and thermal characteristics of cross flow heat exchanger has been put forward. Heat carriers have been modeled by a turbulent motion of compressible and incompressible liquids. The problem is solved using the ANSYS CFX software system. Some peculiarities of the problem solution have been considered including the possibility to intensify the heat exchange by installing two systems of annular airfoils in the heat exchanger.
I Using Porous Material for Heat Transfer Enhancement in Heat Exchangers: Review
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M. A. Delavar
Full Text Available The increase in energy cost and energy consumption has required more effective use of energy. The problem of dissipating high heat fluxes has received much attention due to its importance in applications such as heat exchanger. The heat transfer duty of heat exchangers can be improved by heat transfer enhancement techniques. In recent years, Considerable efforts have been made to increase heat transfer rates in heat exchangers by implementing passive enhancement methods that require no direct consumption of external power. On the basis of a theoretical and experimental analysis the conclusion derived was that the best heat transfer enhancement can be reached by the use of porous material as an inexpensive technique to extend the heat transfer area, improve effective thermal conductivity, and mix fluid flow. This paper presents a brief discussion on the application of using porous media to heat exchangers by means of heat transfer enhancement.
CFD Based Evaluation Of Effectiveness Of Counter Flow Heat Exchanger
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Gurpreet Kour
Full Text Available Engineers are continually being asked to improve effectiveness of heat transfer equipments. These requests may arise as a result of the need to increase profitability or accommodate capital limitations. Processes which use heat transfer equipment i.e. heat exchanger must frequently be improved for these reasons. Artifical roughness is important technique for enhancing the effectiveness of heat exchanger. In this work effectiveness of smooth as well as roughened tube in heat exchanger is theoretically investigated by using ring type roughness geometry. The performance obtained is then compared with smooth tube. Ringed tube has a significant effect on effectiveness of heat exchanger. The effectiveness is 3.2 times as compared with plane tube was reported. The effectiveness found to be increased with increasing roughness and decreasing pitch between the rings.
Theoretical evaluation on the impact of heat exchanger in Advanced Adiabatic Compressed Air Energy Storage system
International Nuclear Information System (INIS)
Highlights: • A multi-stage AA-CAES system model is established based on thermodynamic theory. • Four Cases about pressure loss and effectiveness of heat exchanger are investigated. • The impact of pressure loss on conversion of heat energy in TES is more sensitive. • The impact of heat exchanger effectiveness in charge process on system is stronger. • Pressure loss in heat exchanger affects the change trends of system efficiency. - Abstract: Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) is a large-scale energy storage system based on gas turbine technology and thermal energy storage (TES). Electrical energy can be converted into internal energy of air and heat energy in TES during the charge process, while reverse energy conversion proceeds during discharge process. The performance of AA-CAES system requires further improvement in order to increase efficiency. In this paper, a multi-stage AA-CAES system model is established, and the influence of effectiveness and pressure loss in heat exchanger on energy conversion and utilization efficiency of AA-CAES system is analyzed theoretically based on the theory of thermodynamics. Four Cases about effectiveness and pressure loss of heat exchanger are investigated and compared with each other. It is found that effectiveness and pressure loss of heat exchanger are directly related to energy conversion and utilization in AA-CAES system. System efficiency changes with the variation of heat exchanger effectiveness and the impact of pressure loss on conversion of heat energy in TES is more sensitive than that of internal energy of air. Pressure loss can cause the complexity of system efficiency change. With appropriate selection of the values of heat exchanger effectiveness for both charge and discharge processes, an AA-CAES system with a higher efficiency could be expected
Optimized heat exchanger unit in a thermoacoustic refrigerator
El-Fawal, Mawahib Hassan; Mohd-Ghazali, Normah
Due to concern over the environmental impact caused by hazardous refrigerants, the last ten years or so has seen increasing research into thermoacoustic refrigeration. A thermoacoustic refrigerator is a device which uses acoustic power to pump heat. It holds the merits of simple mechanical design, absence of harmful refrigerants and having no or few moving parts. However, the performance of the thermoacoustic refrigerator, particularly the standing wave types, is currently not competitive compared to its counterpart conventional vapor-compression refrigerator. Thermoacoustic refrigeration prototypes, built up-to-date, achieved 0.1-0.2 relative coefficient of performance (COPR) compared with that of 0.33-0.5 for the conventional vapor-compression refrigerators. The poor heat exchanger design is one of the reasons for this poor efficiency. This paper discussed the influence of the thermoacoustic refrigerator heat exchanger's parameters on its design and the optimization of the performance of the system using the Lagrange multiplier method. The results showed that, the dissipated power is less than the published value by about 49% in the cold heat exchanger and about 38.5% in the hot heat exchanger. Furthermore, the increase of the cold heat exchanger effectiveness is found to be 3%. Thus, the decrease in the dissipated power in both heat exchangers with effective cold heat exchanger increases the performance of the thermoacoustic refrigerator.
An experimental study of a pin-fin heat exchanger
Ramthun, David L.
Approved for public release; distribution is unlimited A detailed experimental study has been carried out on the heat transfer and pressure drop characteristics of a compact heat exchanger with pin fins. A modular wind-tunnel with a rectangular cross-section duct-flow area was constructed that would accommodate the heat exchanger test section with varying pin designs. The flow in the tunnel was achieved through a suction-type blower, and a leading entrance length section was added to achie...
Multi-period design of heat exchanger networks
M. I. Ahmad
Heat exchanger networks are an integral part of chemical processes as they recover available heat and reduce utility consumption, thereby improving the overall economics of an industrial plant. This paper focuses on heat exchanger network design for multi-period operation wherein the operating conditions of a process may vary with time. A typical example is the hydrotreating process in petroleum refineries where the operators increase reactor temperature to compensate for catalyst deactivatio...
Principle of equipartition of entransy dissipation for heat exchanger design
Institute of Scientific and Technical Information of China (English)
In the present work,a principle of equipartition of entransy dissipation(EoED) for heat exchanger design is established,which says that for a heat exchanger design with given heat duty and heat transfer area,the total entransy dissipation rate reaches the minimum when the local entransy dissipation rate is uniformly distributed along the heat exchanger.When the heat transfer coefficient is unfixed,the total entransy dissipation obtained by the EoED principle is less than that obtained by the principle of equipartition of temperature difference(EoTD).Furthermore,the exchanger effectiveness obtained by the EoED principle is larger than that obtained by the EoTD principle.When the heat transfer coefficient is fixed,the EoED principle is equivalent to the EoTD principle.We show that the equipartition of entropy production(EoEP) and EoED principles give rise to difference in entropy generation and entransy dissipation for a heat exchanger optimization design.The discrepancies are caused by distinct features of entropy production minimization and entransy dissipation minimization principles,the former is to optimize the design of heat exchanger by making the lost available work minimum,while the latter is not involved with heat-work conversion.It is found that the entropy generation number is not suitable for evaluating heat exchanger performance,since it directly depends on the inlet and outlet temperatures of working fluids.On the contrary,the entransy dissipation number is not directly related to the inlet and outlet temperatures of working fluids.Therefore,the entransy dissipation number is more suitable for serving as a criterion to evaluate heat exchanger performance.
CFD as a Design Tool for a Concentric Heat Exchanger
Oosterhuis, J.P.; Bühler, S.; Wilcox, D.; Meer, Van Der
A concentric gas-to-gas heat exchanger is designed for application as a recuperator in the domestic boiler industry. The recuperator recovers heat from the exhaust gases of a combustion process to preheat the ingoing gaseous fuel mixture resulting in increased fuel efficiency. This applied study shows the use of computational fluid dynamics (CFD) simulations as an efficient design tool for heat exchanger design. An experimental setup is developed and the simulation results are validated.
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Carmen SANDU (TODERASCU
Full Text Available The experience of recentyears showsthat it hasa fundamentalroleformation mechanismof the exchange rateinmacroeconomic stabilization. Global economiccrises, oil shockshave shownthe difficultyoffloatingsustainabilitybyparticipants in the system. EuropeanMonetary System, focused onconcertedfloatingcurrenciestoECU, was formedunder the conditionsin which somecountries have adoptedregional monetaryarrangements(EU countries, with suchbasescurrencyregimeshybridthat combinesspecific mechanismsto those offixedratefree floating. This paperaims to demonstratethe important role thatithasthe choice ofexchange rateregimeas abasic elementin thefoundationofmacroeconomic stabilizationinstruments. Consideredan expression of thestateof the domestic economyandinternationalcompetitiveness, the exchange rate is determined bya complex set ofexternal factorsorinternalstabilityisa prerequisite forthe crisis.
Flat tube heat exchangers – Direct and indirect noise levels in heat pump applications
International Nuclear Information System (INIS)
In the outdoor unit of an air-source heat pump the fan is a major noise source. The noise level from the fan is dependent on its state of operation: high air-flow and high pressure drop often result in higher noise levels. In addition, an evaporator that obstructs an air flow is a noise source in itself, something that may contribute to the total noise level. To be able to reduce the noise level, heat exchanger designs other than the common finned round tubes were investigated in this study. Three types of heat exchanger were evaluated to detect differences in noise level and air-side heat transfer performance at varying air flow. The measured sound power level from all the heat exchangers was low in comparison to the fan sound power level (direct effect). However, the heat exchanger design was shown to have an important influence on the sound power level from the fan (indirect effect). One of the heat exchangers with flat tubes was found to have the lowest sound power level, both direct and indirect, and also the highest heat transfer rate. This type of flat tube heat exchanger has the potential to reduce the overall noise level of a heat pump while maintaining heat transfer efficiency. - Highlights: •The direct noise from a heat exchanger is negligible in heat pump applications. •The design of the heat exchanger highly influences the noise from an outdoor unit. •Flat tube heat exchangers can reduce the noise from the outdoor unit of a heat pump. •Flat tube heat exchangers can increase the energy efficiency of a heat pump
Energy Technology Data Exchange (ETDEWEB)
Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si
International Nuclear Information System (INIS)
Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm-3 (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si
Optimization of the Single Staggered Wire and Tube Heat Exchanger
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Arsana I Made
Full Text Available Wire and tube heat exchanger consists of a coiled tube, and wire is welded on the two sides of it in normal direction of the tube. Generally,wire and tube heat exchanger uses inline wire arrangement between the two sides, whereas in this study, it used staggered wire arrangement that reduces the restriction of convection heat transfer. This study performed the optimization of single staggered wire and tube heat exchanger to increase the capacity and reduce the mass of the heat exchanger. Optimization was conducted with the Hooke-Jeeves method, which aims to optimize the geometry of the heat exchanger, especially on the diameter (dw and the distance between wires (pw. The model developed to present heat transfer correlations on single staggered wire and tube heat exchanger was valid. The maximum optimization factor obtained when the diameter wire was 0.9 mm and the distance between wires (pw was 11 mm with the fref value = 1.5837. It means that the optimized design only using mass of 59,10 % and could transfer heat about 98,5 % from the basis design.
Xenon Recirculation-Purification with a Heat Exchanger
Giboni, K L; Choi, B; Haruyama, T; Lang, R F; Lim, K E; Melgarejo, A J; Plante, G; 10.1088/1748-0221/6/03/P03002
Liquid-xenon based particle detectors have been dramatically growing in size during the last years, and are now exceeding the one-ton scale. The required high xenon purity is usually achieved by continuous recirculation of xenon gas through a high-temperature getter. This challenges the traditional way of cooling these large detectors, since in a thermally well insulated detector, most of the cooling power is spent to compensate losses from recirculation. The phase change during recondensing requires five times more cooling power than cooling the gas from ambient temperature to -100C (173 K). Thus, to reduce the cooling power requirements for large detectors, we propose to use the heat from the purified incoming gas to evaporate the outgoing xenon gas, by means of a heat exchanger. Generally, a heat exchanger would appear to be only of very limited use, since evaporation and liquefaction occur at zero temperature difference. However, the use of a recirculation pump reduces the pressure of the extracted liquid...
Study of Rankine Cycle System With Phase Change Energy Storage Heat Exchanger%带有相变储能换热器的朗肯循环系统研究
Institute of Scientific and Technical Information of China (English)
杨岑玉; 邹景煌; 赵波; 王乐; 金翼; 宋鹏翔; 杨士慧; 徐进良
A Rankine cycle system with the phase change energy storage heat exchanger is proposed, which can be used in energy-excess area where it has surplus wind energy and solar energy, etc. The characteristic of the system is the use of phase change energy storage heat exchanger as evaporative heat exchanger, which reduces the system's exergy loss by reducing the mean temperature difference between the heat source and the working fluid. Taking the organic Rankine cycle which is driven by the medium and low geothermal water as an example, R245fa is selected as working fluid, and the calculation results show that the exergy loss of phase change energy storage heat exchanger in loop decreases by 17.58%, and the geothermal water's required mass flow rate is only 40.33% of the original data, and the required pump power also decreases. By changing the outlet temperature and superheat temperature of the working fluid and the pinch-point temperature difference, the change rule of the geothermal water mass flow rate, outlet temperature and exergy loss is studied, and the results show that the exergy loss and the mass flow rate of the phase change energy storage heat exchanger in loop is smaller, the pump power loss is reduced, and the exergy efficiency of the system is also improved.%提出一种带有相变储能换热器的朗肯循环系统,可用于风能、太阳能等资源过剩的地区。该系统的特点是利用相变储能换热器充当系统蒸发换热器,减小热源和工质的传热平均温差,减小系统火用损。以中低温地热水为热源驱动的有机朗肯循环为例,选取R245fa为工质,计算结果表明:相变储能换热器所在回路的火用损减小17.58%,且地热水所需质量流量仅为原来的40.33%,所需泵功减小。通过改变工质出口温度、过热度及夹点温差,研究地热水质量流量、出口温度及火用损的变化规律,结果表明:相变储能换热器所在回路的质量流�
Exergy Transfer Characteristics on Low Temperature Heat Exchangers
Wu, S. Y.; Yuan, X. F.; Li, Y. R.; Peng, L.
By analyzing exergy transfer process of the low temperature heat exchangers operating below the surrounding temperature, the concept of exergy transfer coefficient is put forward and the expressions which involving relevant variables for the exergy transfer coefficient, the heat transfer units number and the ratio of cold to hot fluids heat capacity rate, etc. are derived. Taking the parallel flow, counter flow and cross flow low temperature heat exchangers as examples, the numerical results of exergy transfer coefficient are given and the comparison of exergy transfer coefficient with heat transfer coefficient is analyzed.
Investigation of Brazed Plate Heat Exchangers With Variable Chevron Angles
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S. Muthuraman
Full Text Available - Experiments to measure the condensation heat transfer coefficient and the pressure drop in brazed plate heat exchangers (BPHEs were performed with the refrigerants R410A and R22. Brazed plate heat exchangers with different chevron angles of 45°, 35°, and 20° were used. Varying the mass flux, the condensation temperature, and the vapor quality of the refrigerant, we measured the condensation heat transfer coefficient and the pressure drops. Both the heat transfer coefficient and the pressure drop increased proportionally with the mass flux and the vapor quality and inversely with the condensation temperature and the chevron angle.
Improvements of U-pipe Borehole Heat Exchangers
Acuña, José
The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the groun...
Effect of size sprinkled heat exchange surface on developing boiling
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Petr Kracík
Full Text Available This article presents research of sprinkled heat exchangers. This type of research has become rather topical in relation to sea water desalination. This process uses sprinkling of exchangers which rapidly separates vapour phase from a liquid phase. Applications help better utilize low-potential heat which is commonly wasted in utility systems. Low-potential heat may increase utilization of primary materials. Our ambition is to analyse and describe the whole sprinkled exchanger. Two heat exchangers were tested with a similar tube pitch: heat exchanger no. 1 had a four-tube bundle and heat exchanger no. 2 had eight-tube bundle. Efforts were made to maintain similar physical characteristics. They were tested at two flow rates (ca 0.07 and 0.11 kg s−1 m−1 and progress of boiling on the bundle was observed. Initial pressure was ca 10 kPa (abs at which no liquid was boiling at any part of the exchanger; the pressure was then lowered. Other input parameters were roughly similar for both flow rates. Temperature of heating water was ca 50°C at a constant flow rate of ca 7.2 L min−1. Results of our experiments provide optimum parameters for the given conditions for both tube bundles.
Physical explosion analysis in heat exchanger network design
Pasha, M.; Zaini, D.; Shariff, A. M.
The failure of shell and tube heat exchangers is being extensively experienced by the chemical process industries. This failure can create a loss of production for long time duration. Moreover, loss of containment through heat exchanger could potentially lead to a credible event such as fire, explosion and toxic release. There is a need to analyse the possible worst case effect originated from the loss of containment of the heat exchanger at the early design stage. Physical explosion analysis during the heat exchanger network design is presented in this work. Baker and Prugh explosion models are deployed for assessing the explosion effect. Microsoft Excel integrated with process design simulator through object linking and embedded (OLE) automation for this analysis. Aspen HYSYS V (8.0) used as a simulation platform in this work. A typical heat exchanger network of steam reforming and shift conversion process was presented as a case study. It is investigated from this analysis that overpressure generated from the physical explosion of each heat exchanger can be estimated in a more precise manner by using Prugh model. The present work could potentially assist the design engineer to identify the critical heat exchanger in the network at the preliminary design stage.
Integrated system of nuclear reactor and heat exchanger
International Nuclear Information System (INIS)
The invention concerns PWRs in which the heat exchanger is associated with a pressure vessel containing the core and from which it can be selectively detached. This structural configuration applies to electric power generating uses based on land or on board ships. An existing reactor of this kind is fitted with a heat exchanger in which the tubes are 'U' shaped. This particular design of heat exchangers requires that the ends of the curved tubes be solidly maintained in a tube plate of great thickness, hence difficult to handle and to fabricate and requiring unconventional fine control systems for the control rods and awkward coolant pump arrangements. These complications limit the thermal power of the system to level below 100 megawatts. On the contrary, the object of this invention is to provide a one-piece PWR reactor capable of reaching power levels of 1500 thermal megawatts at least. For this, a pressure vessel is provided in the cylindrical assembly with not only a transversal separation on a plane located between the reactor and the heat exchanger but also a cover selectively detachable which supports the fine control gear of the control rods. Removing the cover exposes a part of the heat exchanger for easy inspection and maintenance. Further, the heat exchanger can be removed totally from the pressure vessel containing the core by detaching the cylindrical part, which composes the heat exchanger section, from the part that holds the reactor core on a level with the transversal separation
The influence of heat exchanger design on the synthesis of heat exchanger networks
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Liporace F.S.
Full Text Available Heat exchanger network (HEN synthesis has been traditionally performed without accounting for a more detailed unit design, which is important since the final HEN may require unfeasible units. Recently, publications on this matter have appeared, as well as softwares that simultaneously perform synthesis and units design. However, these publications do not clearly show the influence of the new added features on the final HEN. Hence, this work aims at showing that units' design can strongly affect the final HEN. Improvements on heat transfer area and total annual cost estimations, which influence the HEN structural evolution, are the main responsible for that. It is also shown the influence of some design bounds settings, which can indicate an unfeasible unit design and, therefore, the need for a new match search or the maintenance of a loop. An example reported in the literature is used to illustrate the discussion.
Heat Recovery Ventilation for Housing: Air-to-Air Heat Exchangers.
Corbett, Robert J.; Miller, Barbara
The air-to-air heat exchanger (a fan powered ventilation device that recovers heat from stale outgoing air) is explained in this six-part publication. Topic areas addressed are: (1) the nature of air-to-air heat exchangers and how they work; (2) choosing and sizing the system; (3) installation, control, and maintenance of the system; (4) heat…
Hydraulic Validation of the LHC Cold Mass Heat Exchanger Tube
Provenaz, P
The knowledge of the helium mass flow vs. the fraction of the tube wetted by the liquid helium II in the heat exchanger is a crucial input parameter for the heat exchange since the heat flux is direct ly proportional to the wetted surface. In the range of liquid and gas velocities inside the heat exchanger, the liquid flow behaves like in an open channel. Looking at the flow equations for such a s ituation, the velocity depends on the fluid properties only by the friction factor which is a function of the Reynolds number. Thus it was decided to build an experiment with water in order to check t he open channel equations in the heat exchanger geometry. This paper shows the results for water and gives the extrapolation for helium.
The predictive protective control of the heat exchanger
Nevriva, Pavel; Filipova, Blanka; Vilimec, Ladislav
The paper deals with the predictive control applied to flexible cogeneration energy system FES. FES was designed and developed by the VITKOVICE POWER ENGINEERING joint-stock company and represents a new solution of decentralized cogeneration energy sources. In FES, the heating medium is flue gas generated by combustion of a solid fuel. The heated medium is power gas, which is a gas mixture of air and water steam. Power gas is superheated in the main heat exchanger and led to gas turbines. To protect the main heat exchanger against damage by overheating, the novel predictive protective control based on the mathematical model of exchanger was developed. The paper describes the principle, the design and the simulation of the predictive protective method applied to main heat exchanger of FES.
Experimental investigation of thermal conductivity coefficient and heat exchange between fluidized bed and inclined exchange surface
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B. Stojanovic
Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.
Dynamic thermal simulation of ground heat exchangers for renewable heating of buildings
Gan, Guohui
The temperature of deep soil is relatively stable throughout a year and the thermal energy stored in soil can be used to provide renewable heat or coolth for a building. A ground heat exchanger is required to transfer heat between the fluid in the heat exchanger and surrounding soil. The control volume method is used to solve the equations for coupled heat and moisture transfer in soil and the dynamic interactions between the heat exchanger, soil and atmosphere. The method is used for numeric...
Control strategies in a thermal oil - Molten salt heat exchanger
Roca, Lidia; Bonilla, Javier; Rodríguez-García, Margarita M.; Palenzuela, Patricia; de la Calle, Alberto; Valenzuela, Loreto
This paper presents a preliminary control scheme for a molten salt - thermal oil heat exchanger. This controller regulates the molten salt mass flow rate to reach and maintain the desired thermal oil temperature at the outlet of the heat exchanger. The controller architecture has been tested using an object-oriented heat exchanger model that has been validated with data from a molten salt testing facility located at CIEMAT-PSA. Different simulations are presented with three different goals: i) to analyze the controller response in the presence of disturbances, ii) to demonstrate the benefits of designing a setpoint generator and iii) to show the controller potential against electricity price variations.
Heat Exchanger System Piping Design for a Tube Rupture Event
Wakim, Fadi Antoine; Kavcar, Pinar Cakir; Samad, Mustafa
ABSTRACT: Tube-rupture events in shell and tube heat exchangers can result in significantly high surge pressures. Steady state and dynamic methods can be used to assess the impacts of these events on heat exchanger system piping networks. This paper presents the findings of a set of dynamic surge simulations on the impacts of tube-rupture events in a Propane-Feed Gas Heat Exchanger System. Once adjacent piping design is considered, the Joukowsky formulation-based method is not always appropri...
New counter flow heat exchanger designed for ventilation systems in cold climates
DEFF Research Database (Denmark)
Kragh, Jesper; Rose, Jørgen; Nielsen, Toke Rammer;
In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure...... drop. Preheating the inlet air (outdoor air) to a temperature above 0 degrees C before it enters the exchanger is one solution often used to solve the problem, however, this method reduces the energy saving potential significantly. To minimize the energy cost, a more efficient way to solve the freezing...... problem is therefore desirable. In this paper, the construction and test measurements of a new counter flow heat exchanger designed for cold climates are presented. The developed heat exchanger is capable of continuously defrosting itself without using supplementary heating. Other advantages...
Energy Technology Data Exchange (ETDEWEB)
Bacellar, Daniel [University of Maryland, College Park; Ling, Jiazhen [University of Maryland, College Park; Aute, Vikrant [University of Maryland, College Park; Radermacher, Reinhard [University of Maryland, College Park; Abdelaziz, Omar [ORNL
Air-to-refrigerant heat exchangers are very common in air-conditioning, heat pump and refrigeration applications. In these heat exchangers, there is a great benefit in terms of size, weight, refrigerant charge and heat transfer coefficient, by moving from conventional channel sizes (~ 9mm) to smaller channel sizes (< 5mm). This work investigates new designs for air-to-refrigerant heat exchangers with tube outer diameter ranging from 0.5 to 2.0mm. The goal of this research is to develop and optimize the design of these heat exchangers and compare their performance with existing state of the art designs. The air-side performance of various tube bundle configurations are analyzed using a Parallel Parameterized CFD (PPCFD) technique. PPCFD allows for fast-parametric CFD analyses of various geometries with topology change. Approximation techniques drastically reduce the number of CFD evaluations required during optimization. Maximum Entropy Design method is used for sampling and Kriging method is used for metamodeling. Metamodels are developed for the air-side heat transfer coefficients and pressure drop as a function of tube-bundle dimensions and air velocity. The metamodels are then integrated with an air-to-refrigerant heat exchanger design code. This integration allows a multi-scale analysis of air-side performance heat exchangers including air-to-refrigerant heat transfer and phase change. Overall optimization is carried out using a multi-objective genetic algorithm. The optimal designs found can exhibit 50 percent size reduction, 75 percent decrease in air side pressure drop and doubled air heat transfer coefficients compared to a high performance compact micro channel heat exchanger with same capacity and flow rates.
Low Cost Polymer heat Exchangers for Condensing Boilers
Energy Technology Data Exchange (ETDEWEB)
Butcher, Thomas [Brookhaven National Lab. (BNL), Upton, NY (United States); Trojanowski, Rebecca [Brookhaven National Lab. (BNL), Upton, NY (United States); Wei, George [Brookhaven National Lab. (BNL), Upton, NY (United States); Worek, Michael [Brookhaven National Lab. (BNL), Upton, NY (United States)
Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered to be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.
Slotting Fins of Heat Exchangers to Provide Thermal Breaks
Scull, Timothy D.
Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.
Numerical Analysis of Tube-Fin Heat Exchanger using Fluent
Directory of Open Access Journals (Sweden)
M. V. Ghori
Full Text Available Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of two-row plain Tube and Fin heat exchanger using FLUENT software. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created and meshed by using GAMBIT software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models k-, and SST k-omega, with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated value friction factor f and Colburn factor j to experimental results investigate by Wang. Reasonable agreement is found between the simulations and experimental data, and the fluent software has been sufficient for simulating the flow fields in tube-fin heat exchangers.
Analysis of sensible heat exchanges from a thermal manikin.
Quintela, Divo; Gaspar, Adélio; Borges, Carlos
The present work is dedicated to the analysis of dry heat exchanges as measured by a thermal manikin placed in still air. We believe that the understanding of some fundamental aspects governing fluid flow and heat transfer around three-dimensional bodies such as human beings deserves appropriate attention. This should be of great significance for improving physiological models concerned with thermal exposures. The potential interest of such work can be directed towards quite distinct targets such as working conditions, sports, the military, or healthcare personnel and patients. In the present study, we made use of a climate chamber and an articulated thermal manikin of the Pernille type, with 16 body parts. The most common occidental postures (standing, sitting and lying) were studied. In order to separate heat losses due to radiation and convection, the radiative heat losses of the manikin were significantly reduced by means of a shiny aluminium coating, which was carefully applied to the artificial skin. The air temperature within the test chamber was varied between 13 degrees C and 29 degrees C. The corresponding mean differences between the skin and the operative temperatures changed from 3.8 degrees C up to 15.8 degrees C. The whole-body heat transfer coefficients by radiation and convection for both standing and sitting postures are in good agreement with those in the published literature. The lying posture appears to be more efficient for losing heat by convection. This is confirmed when the heat losses of each individual part are considered. The proposed correlations for the whole body suggest that natural convection is mainly laminar.
Directory of Open Access Journals (Sweden)
S. A. Filatau
Full Text Available Unsteady numerical model of borehole heat exchanger heat regime was developed. General numerical modeling results are borehole heat flux, heat carrier inlet temperature and average soil temperature distribution. Proposed model is based on solution of heat conduction equation in transient plane axially symmetric formulation with boundary conditions for borehole heat exchanger and undisturbed soil domain. Solution method is finite difference method. Numerical model is verified with comparisons numerical results and experimental data from developed laboratory installation for simulation unsteady heat regime of horizontal positioned U-shape ground heat exchanger in sand medium.Cooling of water is organized in ground exchanger in experiment. Experiment includes two steps. Thermal properties of sand is determined at the first stage. Thermal conductivity of sand is determined by stationary plate method, thermal diffusivity is determined by regular regime method using cylindrical calorimeter. Determined properties are used further in processing of experimental results at second step for analysis of transient work of ground heat exchanger. Results of four experiments are analyzed with different duration and time behavior of mass flow and heat carrier temperature. Divergences of experimental and simulated results for temperature of heat carrier changes in the range 0,5–1,8 %, for sand temperature in the range 1,0–2,3 %, for heat flux in the range 3,6–5,4 %. Experimental results can be used for validation of other simulation methods of ground heat exchangers. Presented numerical model can be used for analyzing of heat supply systems with heat pumps.
Investigation of Condensation Heat Transfer Correlation of Heat Exchanger Design in Secondary Passive Cooling System
International Nuclear Information System (INIS)
Recently, condensation heat exchangers have been studied for applications to the passive cooling systems of nuclear plants. To design vertical-type condensation heat exchangers in secondary passive cooling systems, TSCON (Thermal Sizing of CONdenser), a thermal sizing program for a condensation heat exchanger, was developed at KAERI (Korea Atomic Energy Research Institute). In this study, the existing condensation heat transfer correlation of TSCON was evaluated using 1,157 collected experimental data points from the heat exchanger of a secondary passive cooling system for the case of pure steam condensation. The investigation showed that the Shah correlation, published in 2009, provided the most satisfactory results for the heat transfer coefficient with a mean absolute error of 34.8%. It is suggested that the Shah correlation is appropriate for designing a condensation heat exchanger in TSCON
Liquid metal heat transfer in heat exchangers under low flow rate conditions
International Nuclear Information System (INIS)
The present paper describes the liquid metal heat transfer in heat exchangers under low flow rate conditions. Measured data from some experiments indicate that heat transfer coefficients of liquid metals at very low Péclet number are much lower than what are predicted by the well-known empirical relations. The cause of this phenomenon was not fully understood for many years. In the present study, one countercurrent-type heat exchanger is analyzed using three, separated countercurrent heat exchanger models: one is a heat exchanger model in the tube bank region, while the upper and lower plena are modeled as two heat exchangers with a single heat transfer tube. In all three heat exchangers, the same empirical correlation is used in the heat transfer calculation on the tube and the shell sides. The Nusselt number, as a function of the Péclet number, calculated from measured temperature and flow rate data in a 50 MW experimental facility was correctly reproduced by the calculation result, when the calculated result is processed in the same way as the experiment. Finally, it is clarified that the deviation is a superficial phenomenon which is caused by the heat transfer in the plena of the heat exchanger. (author)
Process Heat Exchanger Options for Fluoride Salt High Temperature Reactor
Energy Technology Data Exchange (ETDEWEB)
Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson
The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.
Process Heat Exchanger Options for the Advanced High Temperature Reactor
Energy Technology Data Exchange (ETDEWEB)
Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson
The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.
Shell-and-Tube or Plate Heat Exchangers
Kuzma-Kichta, Y; Savelyev, P; Lodvikov, K
The calculations of heat and hydraulic characteristics and influence of apparatus with intensifiers size analysis to heat exchanger potential of equipment were made onto the basis of known experimental data recommendations. Calculations data were received in a range of parameters, that are typical for a heat and water supply systems. It was obtain, that in studied range of Reynolds's number, the most better heat transfer coefficient value is for the tubes with dimpled interface...
Thermal design heat sinks, thermoelectrics, heat pipes, compact heat exchangers, and solar cells
Lee, H S
The proposed is written as a senior undergraduate or the first-year graduate textbook,covering modern thermal devices such as heat sinks, thermoelectric generators and coolers, heat pipes, and heat exchangers as design components in larger systems. These devices are becoming increasingly important and fundamental in thermal design across such diverse areas as microelectronic cooling, green or thermal energy conversion, and thermal control and management in space, etc. However, there is no textbook available covering this range of topics. The proposed book may be used as a capstone design cours
International Nuclear Information System (INIS)
Boiling at microscales is a challenging problem for the computational models as well as the resources. During boiling, the formation and departure of vapor bubbles from the heated surface involves the physics from nano/micro level to the macro level. Therefore, a hierarchical methodology is needed to incorporate the nano/microscale physics with the macroscale system performance. Using micro-fabrication techniques, microstructures (micropin-fins) can be fabricated around the tubes in the heat exchanger of Pressurized Water Reactors (PWRs) to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. Combined with high fidelity simulations of the thermal transport in the entire system, optimal design of microstructure patterns and layouts can be worked out pragmatically. Properly patterned microstructures on the pipe in the steam generation zone should create more nuclei for bubble to form and result in a reduced average bubble size and shorter retention time, i.e. the time for the vapor phase sticking on the pipe surface. The smaller average steam bubble size and shorter bubble retention time will enhance the overall thermal efficiency. As a preliminary step, a periodic arrangement of micropin-fins containing four in-line cylindrical fins was modeled. The governing equations for the mass, momentum and energy transport were solved in the fluid in a conjugate heat transfer mode. In the future, several studies will be conducted to simulate different geometric arrangements, different fin cross-sections, and realistic operating conditions including phase-change with boiling by adding complexities in simple steps
Some extra-high capacity heat exchangers of special design
International Nuclear Information System (INIS)
Recent technical advances in developing high-capacity power generating equipment, in using new heat transfer media, in seawater desalination, and in chemical processing require the development of higher unit-capacity heat exchangers. Up-to-date solutions illustrating the progress made in the development of such heat exchangers is discussed and suggestions are made which may be of interest in this field. Specific heat transfer systems discussed include systems for air-cooled condensing power plants, multiple reheating cycles for steam turbines, and systems using liquid lead as the transfer medium. (U.S.)
On Effectiveness and Entropy Generatioin in Heat Exchanger
Institute of Scientific and Technical Information of China (English)
XiongDaxi; LiZhixin; 等
Some conceptual problems were discussed in the present paper,Firstly,according to the physical meaning of effectiveness,a new expression of effectiveness was developed by using an ideal heat exchnager model and temperature histogram method,in which the non-uniform inlet temperature profile was considered.Secondly,the relation of entropy generation number to effectiveness was studied,it was pointed out that both of them could express the perfect degree of a heat exchanger to the second thermodynamic law.Finally,to describe both quantity and quality of heat transferred in a heat exchanger a criterion named as comperhensive thermal performance coefficient (CTPE) was presented.
Various methods to improve heat transfer in exchangers
Directory of Open Access Journals (Sweden)
Pavel Zitek
Full Text Available The University of West Bohemia in Pilsen (Department of Power System Engineering is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors. For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production. In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
Effect of flow twisting on hydraulic resistance and heat exchange
Suslov, V. Ya.; Makarov, N. A.
On the basis of dimensional analysis through a differentiated approach to the dimensions of length we have obtained formulas for the effect of flow twisting in a circular tube on the hydraulic resistance and exchange of heat.
Experimental and Numerical Comparison of Two Borehole Heat Exchangers
DEFF Research Database (Denmark)
Alberdi Pagola, Maria; Poulsen, Søren Erbs
This report outlines key results from a comparative study of two different pipe borehole heat exchanger (BHE) configurations. The work was carried out by VIA University College and in collaboration with GM Plast A/S....
High Effectiveness Heat Exchanger for Cryogenic Refrigerators Project
National Aeronautics and Space Administration — We propose an innovative high performance cryogenic heat exchanger manufactured of titanium by photo-etching and diffusion bonding. This is a parallel plate design...
1-MWE heat exchangers for OTEC. Final design report
Energy Technology Data Exchange (ETDEWEB)
Sprouse, A.M.
The design of a 1 MWe OTEC heat exchanger is documented, including the designs of the evaporator and associated systems, condenser, instrumentation, and materials for corrosion/erosion control and fabrication processes. (LEW)
Analysis of induced temperature anomalies along borehole heat exchangers
Lindner, Michael; Schelenz, Sophie; Stollberg, Reiner; Gossel, Wolfgang; Dietrich, Peter; Vienken, Thomas
Over the last years, the thermal use of the shallow subsurface for heat generation, cooling, and thermal energy storage has increased. However, the injection or extraction of heat potentially drives changes in the subsurface temperature regime; especially in urban areas. The presented case study investigates the intensive use of borehole heat exchangers (BHE) and their potential thermal impacts on subsurface temperatures, as well as thermal interactions between individual BHE's for a residential neighborhood in Cologne, Germany. Based on on-site subsurface parameterization, a 3D subsurface model was designed, using the finite element software FEFLOW (DHI WASY). The model contains five BHE, extracting 8.2 kW, with a maximum BHE depth of 38 m, whereby the thickness of the unsaturated zone is 22 m. The simulated time span is 10 years. This study focusses on two questions: How will different BHE arrangements vary in terms of temperature plume formation and potential system interaction and what is the influence of seasonal subsurface heat storage on soil and ground water temperatures.
Heat pipe heat exchanger and its potential to energy recovery in the tropics
Directory of Open Access Journals (Sweden)
Yau Yat H.
Full Text Available The heat recovery by the heat pipe heat exchangers was studied in the tropics. Heat pipe heat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24°C in this study. The performance of the heat pipe heat exchangers was recorded during the one week of operation (168 hours to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heat pipe heat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heat pipe heat exchanger was also investigated. In addition, heat pipe heat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.
Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage Project
National Aeronautics and Space Administration — Current manned spacecraft heat rejection systems use two heat exchangers and an intermediate fluid loop to provide isolation between the crew compartment air and...
Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage Project
National Aeronautics and Space Administration — Advanced Cooling Technologies, Inc. (ACT), supported by Hamilton Sundstrand, proposes to develop a heat pipe heat exchanger that is low mass and provides two levels...
Thermal performance modeling of cross-flow heat exchangers
Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria
This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges
Controllability and Operability Analysis of Heat Exchanger Networks Including Bypasses
Hernández, S; Balcazar-López, L.; Sánchez-Márquez, J. A.; González-García, G.
In this paper, the influence of bypasses in heat exchanger networks on theoretical control properties and closed-loop behavior was investigated. According to theoretical control properties obtained using the singular value decomposition technique, the presence of bypasses increases flexibility of the heat exchanger network. This result was corroborated using closed-loop dynamic simulations using a proportional integral controller and a proportional integral controller with dynamic estimati...
Theoretical and experimental studies of crossflow minichannel heat exchanger subjected to external heat ingress
International Nuclear Information System (INIS)
The effect of heat in-leak, an unavoidable phenomenon occurring due to the temperature difference between the system and its surroundings, has been studied for two-stream crossflow minichannel heat exchangers with unmixed fluids. Assuming that the amount of heat in-leak is known, an analytical expression for the normalised temperature difference between hot and cold fluids has been derived in terms of dimensionless parameters. The analytical results, in conjugation with the area partitioning of crossflow heat exchanger both in x and y directions, have been used for predicting the outlet fluid temperatures. On the experimental part, one of the end plates in a crossflow-type multistream, minichannel heat exchanger has been subjected to deliberate external heat input given electrically. The variation in the exit fluid temperatures has been recorded as a function of this external heat in-leak entering the exchanger through one of its outer surfaces. Experimental data obtained is employed to validate the fluid exit temperatures predicted by the developed model under the same conditions of external heat ingress. - Highlights: • Theoretical model of crossflow heat exchanger with known ambient heat leak amount. • Numerical technique of partitioning exchanger into smaller segments. • Experimental validation of model by testing of crossflow minichannel heat exchanger
ÖZSOLAK, Onur; ESEN, Mehmet
In the following study, 12 m2 test chamber was heated by solar and ground source heat pump under the physical conditions of Elazığ. In order to place slinky heat exchanger pipes, a hole was dug with 1 meter width, 2 meters depth and 15 meters length. Slinky pipes were put horizontally in the hole and water-antifreeze mixture was circulated with the circulating pump in the slinky heat exchanger. The heat taken from the ground was transferred into the environment to be heated through the heat p...
A fundamentally new approach to air-cooled heat exchangers.
Energy Technology Data Exchange (ETDEWEB)
Koplow, Jeffrey P.
We describe breakthrough results obtained in a feasibility study of a fundamentally new architecture for air-cooled heat exchangers. A longstanding but largely unrealized opportunity in energy efficiency concerns the performance of air-cooled heat exchangers used in air conditioners, heat pumps, and refrigeration equipment. In the case of residential air conditioners, for example, the typical performance of the air cooled heat exchangers used for condensers and evaporators is at best marginal from the standpoint the of achieving maximum the possible coefficient of performance (COP). If by some means it were possible to reduce the thermal resistance of these heat exchangers to a negligible level, a typical energy savings of order 30% could be immediately realized. It has long been known that a several-fold increase in heat exchanger size, in conjunction with the use of much higher volumetric flow rates, provides a straight-forward path to this goal but is not practical from the standpoint of real world applications. The tension in the market place between the need for energy efficiency and logistical considerations such as equipment size, cost and operating noise has resulted in a compromise that is far from ideal. This is the reason that a typical residential air conditioner exhibits significant sensitivity to reductions in fan speed and/or fouling of the heat exchanger surface. The prevailing wisdom is that little can be done to improve this situation; the 'fan-plus-finned-heat-sink' heat exchanger architecture used throughout the energy sector represents an extremely mature technology for which there is little opportunity for further optimization. But the fact remains that conventional fan-plus-finned-heat-sink technology simply doesn't work that well. Their primary physical limitation to performance (i.e. low thermal resistance) is the boundary layer of motionless air that adheres to and envelops all surfaces of the heat exchanger. Within this
Oil Circulation Effects on Evaporation Heat Transfer in Brazed Plate Heat Exchanger using R134A
Jang, Jaekyoo; Chang, Youngsoo; Kang, Byungha
Experimental study was performed for oil circulation effects on evaporation heat transfer in the brazed type plate heat exchangers using R134A. In this study, distribution device was installed to ensure uniform flow distribution in the refrigerant flow passage, which enhances heat transfer performance of plate type heat exchanger. Tests were conducted for three evaporation temperature; 33℃, 37℃, and 41℃ and several oil circulation conditions. The nominal conditions of refrigerant are as follo...
Development of User-Friendly Software to Design Dairy Heat Exchanger and Performance Evaluation
The paper proposes a calculation algorithm and development of a software in Visual Basic(Visual Studio 2012 Express Desktop) used in heat transfer studies when different heat exchangers are involved (e.g. Helical Type Triple Tube Heat Exchanger , Plate Type Heat Exchanger).It includes the easy calculation of heat transfer coefficient and followed by the design and simulation of heat exchanger design parameter by inputting general known parameters of a heat exchanger into the devel...
The fouling in the tubular heat exchanger of Algiers refinery
Harche, Rima; Mouheb, Abdelkader; Absi, Rafik
Crude oil fouling in refinery preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer and pressure drops. In subject of this work is an experimental determination of the thermal fouling resistance in the tubular heat exchanger of the crude oil preheats trains installed in an Algiers refinery. By measuring the inlet and outlet temperatures and mass flows of the two fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the two cells of exchangers studies, showed that the fouling resistance increased with time presented an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the impact between the particles. The bad cleaning of the heat exchangers involved the absence of the induction period and caused consequently, high values of the fouling resistance in a relatively short period of time.
Brazed aluminum, Plate-fin heat exchangers for OTEC
Energy Technology Data Exchange (ETDEWEB)
Foust, H.D.
Brazed aluminum plate-fin heat exchangers have been available for special applications for over thirty years. The performance, compactness, versatility, and low cost of these heat exchangers has been unequaled by other heat exchanger configuration. The application of brazed aluminum has been highly limited because of necessary restrictions for clean non-corrosive atmospheres. Air and gas separation have provided ideal conditions for accepting brazed aluminum and in turn have benefited by the salient features of these plate-fin heat exchangers. In fact, brazed aluminum and cryogenic gas and air separation have become nearly synonymous. Brazed aluminum in its historic form could not be considered for a seawater atmosphere. However, technology presents a new look of significant importance to OTEC in terms of compactness and cost. The significant technological variation made was to include one-piece hollow extensions for the seawater passages. Crevice corrosion sites are thereby entirely eliminated and pitting corrosion attack will be controlled by an integral and sacrificial layer of a zinc-aluminum alloy. This paper on brazed aluminum plate-fin heat exchangers for OTEC will aquaint the reader with the state-of-art and variations suggested to qualify this form of aluminum for seawater use. In order to verify the desirable cost potential for OTEC, Trane teamed with Westinghouse to perform an OTEC system analysis with this heat exchanger. These results are very promising and reported in detail elsewhere.
Tube welding of heat exchange surfaces
International Nuclear Information System (INIS)
Many years experience of exploitation of a great number of butts of similar steels, made by partial fusion and with heating by high-frequency current is analysed. Their high reliability and capability of operation are observed. Taking into account the requirements of ducers of power-generating equipment, it is concluded, that subsequent development of tube butt welding by pressure must follow the way: increase of welded tube nomenclature (by diameter and thickness of the wall); improvement of methods of removing internal fin or the introduction of finless welding methods; wide use of instruments of the process parameters control and application of nondestructive control methods. It is shown, that the increase of reliability of the welded joints of tubes of similar steels (austenitic and perlitic) may be achieved by the change of the joint construction, using special spaciers and tubes of perlitic steel, containing carbide-forming elements, which exclude the softening of perlitic steel near the butt in the process of the steel operation
Active latent heat storage with a screw heat exchanger - experimental results for heat transfer and concept for high pressure steam
Zipf, Verena; Willert, Daniel; Neuhäuser, Anton
An innovative active latent heat storage concept was invented and developed at Fraunhofer ISE. It uses a screw heat exchanger (SHE) for the phase change during the transport of a phase change material (PCM) from a cold to a hot tank or vice versa. This separates heat transfer and storage tank in comparison to existing concepts. A test rig has been built in order to investigate the heat transfer coefficients of the SHE during melting and crystallization of the PCM. The knowledge of these characteristics is crucial in order to assess the performance of the latent heat storage in a thermal system. The test rig contains a double shafted SHE, which is heated or cooled with thermal oil. The overall heat transfer coefficient U and the convective heat transfer coefficient on the PCM side hPCM both for charging and discharging have been calculated based on the measured data. For charging, the overall heat transfer coefficient in the tested SHE was Uch = 308 W/m2K and for discharging Udis = 210 W/m2K. Based on the values for hPCM the overall heat transfer coefficients for a larger SHE with steam as heat transfer fluid and an optimized geometry were calculated with Uch = 320 W/m2K for charging and Udis = 243 W/m2K for discharging. For pressures as high as p = 100 bar, an SHE concept has been developed, which uses an organic fluid inside the flight of the SHE as working media. With this concept, the SHE can also be deployed for very high pressure, e.g. as storage in solar thermal power plants.
Materials for nuclear diffusion-bonded compact heat exchangers
International Nuclear Information System (INIS)
This paper discusses the characteristics of materials used in the manufacture of diffusion bonded compact heat exchangers. Heatric have successfully developed a wide range of alloys tailored to meet process and customer requirements. This paper will focus on two materials of interest to the nuclear industry: dual certified SS316/316L stainless steel and nickel-based alloy Inconel 617. Dual certified SS316/316L is the alloy used most widely in the manufacture of Heatric's compact heat exchangers. Its excellent mechanical and corrosion resistance properties make it a good choice for use with many heat transfer media, including water, carbon dioxide, liquid sodium, and helium. As part of Heatric's continuing product development programme, work has been done to investigate strengthening mechanisms of the alloy; this paper will focus in particular on the effects of nitrogen addition. Another area of Heatric's programme is Alloy 617. This alloy has recently been developed for diffusion bonded compact heat exchanger for high temperature nuclear applications, such as the intermediate heat exchanger (IHX) for the very high temperature nuclear reactors for production of electricity, hydrogen and process heat. This paper will focus on the effects of diffusion bonding process and cooling rate on the properties of alloy 617. This paper also compares the properties and discusses the applications of these two alloys to compact heat exchangers for various nuclear processes. (author)
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, H.J.H.; Geld, van der C.W.M.
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall c
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
Jong, de J.A.; Wijnant, Y.H.; Boer, de A.
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic s
Sprinkled Heat Exchangers in Evaporation Mode
Directory of Open Access Journals (Sweden)
Pospisil J.
Full Text Available The paper presents research on the heat transfer at sprinkled tube bundles situated in a test chamber at atmospheric pressure and low-pressure. Dynamic effects of physical quantities influencing the heat transfer coefficient during boiling are examined experimentally. Experimental results were achieved by means of balance measuring using thermocouple probes and by analysis of thermal diagrams created during operation periods.
Capillary pumped loop body heat exchanger
Swanson, Theodore D. (Inventor); Wren, deceased, Paul (Inventor)
A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.
Heat exchanger selection and design analyses for metal hydride heat pump systems
DEFF Research Database (Denmark)
Mazzucco, Andrea; Voskuilen, Tyler G.; Waters, Essene L.;
the most efficient heat exchanger design and provides outcomes generally valid in a pre-design stage. Heat transfer effectiveness is the principal performance parameter guiding the selection analysis, the results of which appear to be mildly (up to 13%) affected by the specific Nusselt correlation used......This study presents a design analysis for the development of highly efficient heat exchangers within stationary metal hydride heat pumps. The design constraints and selected performance criteria are applied to three representative heat exchangers. The proposed thermal model can be applied to select....... The thermo-physical properties of the heat transfer medium and geometrical parameters are varied in the sensitivity analysis, suggesting that the length of independent tubes is the physical parameter that influences the performance of the heat exchangers the most. The practical operative regions for each...
Entropy resistance analyses of a two-stream parallel flow heat exchanger with viscous heating
Institute of Scientific and Technical Information of China (English)
Cheng Xue-Tao; Liang Xin-Gang
Heat exchangers are widely used in industry,and analyses and optimizations of the performance of heat exchangers are important topics.In this paper,we define the concept of entropy resistance based on the entropy generation analyses of a one-dimensional heat transfer process.With this concept,a two-stream parallel flow heat exchanger with viscous heating is analyzed and discussed.It is found that the minimization of entropy resistance always leads to the maximum heat transfer rate for the discussed two-stream parallel flow heat exchanger,while the minimizations of entropy generation rate,entropy generation numbers,and revised entropy generation number do not always.
A Freezable Heat Exchanger for Space Suit Radiator Systems
Nabity, James A.; Mason, Georgia R.; Copeland, Robert J.; Trevino, Luis a.
During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut s metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Radiators have no moving parts and are thus highly reliable. Past freezable radiators have been too heavy, but the weight can be greatly reduced by placing a small and freeze tolerant heat exchanger between the astronaut and radiator, instead of making the very large radiator freeze tolerant. Therefore, the key technological innovation to improve space suit radiator performance was the development of a lightweight and freezable heat exchanger that accommodates the variable heat load generated by the astronaut. Herein, we present the heat transfer performance of a newly designed heat exchanger that endured several freeze / thaw cycles without any apparent damage. The heat exchanger was also able to continuously turn down or turn up the heat rejection to follow the variable load.
Optimization principle of operating parameters of heat exchanger by using CFD simulation
Directory of Open Access Journals (Sweden)
Mičieta Jozef
Full Text Available Design of effective heat transfer devices and minimizing costs are desired sections in industry and they are important for both engineers and users due to the wide-scale use of heat exchangers. Traditional approach to design is based on iterative process in which is gradually changed design parameters, until a satisfactory solution is achieved. The design process of the heat exchanger is very dependent on the experience of the engineer, thereby the use of computational software is a major advantage in view of time. Determination of operating parameters of the heat exchanger and the subsequent estimation of operating costs have a major impact on the expected profitability of the device. There are on the one hand the material and production costs, which are immediately reflected in the cost of device. But on the other hand, there are somewhat hidden costs in view of economic operation of the heat exchanger. The economic balance of operation significantly affects the technical solution and accompanies the design of the heat exchanger since its inception. Therefore, there is important not underestimate the choice of operating parameters. The article describes an optimization procedure for choice of cost-effective operational parameters for a simple double pipe heat exchanger by using CFD software and the subsequent proposal to modify its design for more economical operation.
Optimization principle of operating parameters of heat exchanger by using CFD simulation
Mičieta, Jozef; Jiří, Vondál; Jandačka, Jozef; Lenhard, Richard
Design of effective heat transfer devices and minimizing costs are desired sections in industry and they are important for both engineers and users due to the wide-scale use of heat exchangers. Traditional approach to design is based on iterative process in which is gradually changed design parameters, until a satisfactory solution is achieved. The design process of the heat exchanger is very dependent on the experience of the engineer, thereby the use of computational software is a major advantage in view of time. Determination of operating parameters of the heat exchanger and the subsequent estimation of operating costs have a major impact on the expected profitability of the device. There are on the one hand the material and production costs, which are immediately reflected in the cost of device. But on the other hand, there are somewhat hidden costs in view of economic operation of the heat exchanger. The economic balance of operation significantly affects the technical solution and accompanies the design of the heat exchanger since its inception. Therefore, there is important not underestimate the choice of operating parameters. The article describes an optimization procedure for choice of cost-effective operational parameters for a simple double pipe heat exchanger by using CFD software and the subsequent proposal to modify its design for more economical operation.
Characteristics of Vertical Mantle Heat Exchangers for Solar Water Heaters
DEFF Research Database (Denmark)
Shah, Louise Jivan; Morrison, G.L.; Behnia, M.
- The flow structure in vertical mantle heat exchangers was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the mantle were measured using a particle Image Velocimetry (PIV) system. A CFD simulation model of vertical mantle heat...
CFD as a Design Tool for a Concentric Heat Exchanger
Oosterhuis, J.P.; Bühler, S.; wilcox, D; Meer, van der T.H.
A concentric gas-to-gas heat exchanger is designed for application as a recuperator in the domestic boiler industry. The recuperator recovers heat from the exhaust gases of a combustion process to preheat the ingoing gaseous fuel mixture resulting in increased fuel efficiency. This applied study sho
Flow mechanism and heat transfer enhancement in longitudinal-flow tube bundle of shell-and-tube heat exchanger
Institute of Scientific and Technical Information of China (English)
LIU Wei; LIU ZhiChun; WANG YingShuang; HUANG SuYi
ormer is superior to that of the latter.Compared with rod baffle heat exchanger,heat transfer coefficient of the heat exchanger under investigation is higher under same pressure drop,especially under the high Reynolds numbers.
Numerical and Experimental Investigation for Heat Transfer Enhancement by Dimpled Surface Heat Exchanger in Thermoelectric Generator
Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi
For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.
Carbon-Fiber Brush Heat Exchangers
Knowles, Timothy R.
Velvetlike and brushlike pads of carbon fibers have been proposed for use as mechanically compliant, highly thermally conductive interfaces for transferring heat. A pad of this type would be formed by attaching short carbon fibers to either or both of two objects that one desires to place in thermal contact with each other. The purpose of using a thermal-contact pad of this or any other type is to reduce the thermal resistance of an interface between a heat source and a heat sink.
Analysis of thermosyphon heat exchangers for use in solar domestic hot water heating systems
Dahl, Scott David
A recent innovation in the solar industry is the use of thermosyphon heat exchangers. Determining the performance of these systems requires knowledge of how thermosyphon flow rate and heat exchanger performance vary with operating conditions. This study demonstrates that several thermosyphon heat exchanger designs operate in the laminar mixed convection regime. Empirical heat transfer and pressure drop correlations are obtained for three tube-in-shell heat exchangers (four, seven, and nine tube). Thermosyphon flow is on the shell side. Correlations are obtained with uniform heat flux on the tube walls and with a mixture of glycol and water circulating inside the tubes. Ranges of Reynolds, Prandtl, and Grashof numbers are 50 to 1800, 2.5 and 6.0, and 4×105 to 1×108, respectively. Nusselt number correlations are presented in a form that combines the contributions of forced and natural convection, Nu4Mixed=Nu4Forced+Nu4Natural. The Nusselt number is influenced by natural convection when the term Raq0.25/(Re0.5Pr0.33) is greater than unity. Pressure drop through these three designs is not significantly affected by mixed convection because most pressure drop losses are at the heat exchanger inlet and outlet. A comparison and discussion of the performance of several other heat exchanger designs (tube-in-shell and coil-in- shell designs) are presented. Generally, the coil-in- shell heat exchangers perform better than the tube-in- shell heat exchangers. Data from all heat exchanger designs is used to develop a new one-dimensional model for thermosyphon heat exchangers in solar water heating systems. The model requires two empirically determined relationships, pressure drop as a function of water mass flow rate and the overall heat transfer coefficient-area product (UA) as a function of Reynolds, Prandtl, and Grashof number. A testing protocol is presented that describes the procedure to obtain the data for the correlations. Two new TRNSYS component models are presented
Renormalized anisotropic exchange for representing heat assisted magnetic recording media
Energy Technology Data Exchange (ETDEWEB)
Jiao, Yipeng; Liu, Zengyuan; Victora, R. H., E-mail: email@example.com [MINT Center, Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.
Renormalized anisotropic exchange for representing heat assisted magnetic recording media
International Nuclear Information System (INIS)
Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation
Performance Prediction of Cross-finned Tube Heat Exchangers
Kondou, Chieko; Senshu, Takao; Matsumura, Kenji; Oguni, Kensaku
An important issue in heat pumps is increasing their efficiency, in order to achieve a significant optimization for heat exchangers. Techniques to simulate the flow length averaged heat transfer coefficient and static pressure drop through the flow passage are presented in this paper. In addition, an analytical evaluation of the cost reduction for a cross-fined tube heat exchanger of outdoor heat pump units is instantiated. The dimensionless factors, Colburn's factor j and Fanning's friction factor f, express the heat transfer performance and frictional characteristics, as a function of Reynolds number. These depend on slit possession, an original parameter used in this study. Further, this paper describes an approximate expression of the fin efficiency, which can be used for to survey the fin parameters. The above three concepts were necessary to forecast the performance on the airside. In the results, the cost minimum point was obtained with a comparable performance.
A three-dimensional numerical analysis of complete crossflow heat exchangers with conjugate heat transfer
Perčić, Marko; Lenić, Kristian; TRP, Anica
In this paper, a three dimensional numerical analysis of turbulent fluid flow and heat transfer on the air-side and water-side of plain fin-and-tube heat exchangers is performed in order to obtain their heat transfer characteristics with non-constant physical properties. Besides convection heat transfer on water and air sides, the heat conduction through pipe walls and fins is also considered in the study. The two types of heat exchangers having cascade and in-line flat tube arrangements are ...
Heat Transfer Analysis of the Passive Residual Heat Removal Heat Exchanger
Energy Technology Data Exchange (ETDEWEB)
Zhang, Wenwen; Tian, Wenxi; Su, Guanghui; Qiu, Suizheng [Jiaotong University, Shaanxi (China)
In the present study, thermal-hydraulics characteristics of AP1000 passive residual heat removal heat exchanger (PRHR-HX) at initial operating stage were analyzed based on the porous media models. The data predicated by RELAP5 under the condition of the station blackout was employed as the inlet flow rate and temperature boundary of CFD calculation. The heat transfer from the primary side coolant to the in-containment refueling water storage tank (IRWST) side fluid was calculated in a three-dimensional geometry during iterations, and the distributed resistances were added into the C-type tube bundle regions. Three-dimensional distributions of velocity and temperature in the IRWST were calculated by the CFD code ANSYS FLUENT. The primary temperature, heat transfer coefficients of two sides and the heat transfer were obtained using the coupled heat transfer between the primary side and the IRWST side. The simulation results indicated that the water temperature rises gradually which leads to a thermal stratification phenomenon in the tank and the heat transfer capability decreases with an increase of water temperature. The present results indicated that the method containing coupled heat transfer from the primary side fluid to IRWST side fluid and porous media model is a suitable approach to study the transient thermal-hydraulics of PRHR/IRWST.
Active heat exchange system development for latent heat thermal energy storage
Energy Technology Data Exchange (ETDEWEB)
Lefrois, R.T.; Knowles, G.R.; Mathur, A.K.; Budimir, J.
The report describes active heat exchange concepts for use with thermal energy storage systems in the temperature range of 250/sup 0/C to 350/sup 0/C, using the heat of fusion of molten salts for storing thermal energy. It identifies over 25 novel techniques for active heat exchange thermal energy storage systems. Salt mixtures that freeze and melt in appropriate ranges are identified and are evaluated for physico-chemical, economic, corrosive and safety characteristics. Eight active heat exchange concepts for heat transfer during solidification are conceived and conceptually designed for use with selected storage media. The concepts are analyzed for their scalability, maintenance, safety, technological development and costs. A model for estimating and scaling storage system costs is developed and is used for economic evaluation of salt mixtures and heat exchange concepts for a large scale application. The importance of comparing salts and heat exchange concepts on a total system cost basis, rather than the component cost basis alone, is pointed out. Comparison of these costs with current state-of-the-art systems should be avoided due to significant differences in developmental status. The heat exchange concepts were sized and compared for 6.5 MPa/281/sup 0/C steam conditions and a 1000 MW(t) heat rate for six hours. A cost sensitivity analysis for other design conditions is also carried out. The study resulted in the selection of a shell and coated-tube heat exchanger concept and a direct contact-reflux boiler heat exchange concept. For the storage medium, a dilute eutectic mixture of 99 wt % NaNO/sub 3/ and 1 wt % NaOH is selected for use in experimenting with the selected heat exchanger concepts in subsequent tasks.
An innovative plate heat exchanger of enhanced compactness
International Nuclear Information System (INIS)
In the framework of CEA R&D program to develop the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID), the present work aims to demonstrate the industrial interest of an innovative compact heat exchanger technology. In fact, one of the main innovations of the ASTRID reactor could be the use of a Brayton Gas-power conversion system, in order to avoid the energetic sodium–water interaction that might occur if a traditional Rankine cycle was used. The present work aims to study the thermal-hydraulic performance of the innovative compact heat exchanger concept. Hence, thanks to a trustful numerical model, friction factor and heat transfer correlations are obtained. Then, a global compactness comparison strategy is proposed, taking into account design constraints. Finally, it is demonstrated that the innovative heat exchanger concept is more compact then other already industrial technologies of interest, showing that is can be considered to warrant serious consideration for future ASTRID design as well as for any industrial application that needs very compact heat exchanger technologies. - Highlights: • We propose a new innovative compact heat exchanger technology. • We provide thermal-hydraulic correlations for designers. • We provide a comparison strategy with existing technologies. • We demonstrate the industrial interest of the innovative concept
Heat Transfer Analysis of Passive Residual Heat Removal Heat Exchanger under Natural Convection Condition in Tank
Directory of Open Access Journals (Sweden)
Qiming Men
Full Text Available Aiming at the heat transfer calculation of the Passive Residual Heat Removal Heat Exchanger (PRHR HX, experiments on the heat transfer of C-shaped tube immerged in a water tank were performed. Comparisons of different correlation in literatures with the experimental data were carried out. It can be concluded that the Dittus-Boelter correlation provides a best-estimate fit with the experimental results. The average error is about 0.35%. For the tube outside, the McAdams correlations for both horizontal and vertical regions are best-estimated. The average errors are about 0.55% for horizontal region and about 3.28% for vertical region. The tank mixing characteristics were also investigated in present work. It can be concluded that the tank fluid rose gradually which leads to a thermal stratification phenomenon.
Heat exchangers selection, rating, and thermal design
Kakaç, Sadik; Pramuanjaroenkij, Anchasa
Praise for the Bestselling Second EditionThe first edition of this work gathered in one place the essence of important information formerly scattered throughout the literature. The second edition adds the following new information: introductory material on heat transfer enhancement; an application of the Bell-Delaware method; new correlation for calculating heat transfer and friction coefficients for chevron-type plates; revision of many of the solved examples and the addition of several new ones.-MEMagazine
Measurement of the thermal performance of a Borehole Heat Exchanger while injecting air bubbles in the groundwater
Calzada i Oliveras, Eduard
The most common way to exchange heat with the ground in Ground Source Heat Pump (GSHP) applications is with borehole heat exchangers (energy col-lectors in vertical wells). These boreholes contain the pipe with the secondary fluid of the GSHP and they are often filled with natural groundwater. It has been recently discovered that injecting air bubbles in the groundwater side of the boreholes increases the efficiency of the heat transfer. The aim of this thesis is to analyze the thermal change...
Evaluation of ORC modules performance adopting commercial plastic heat exchangers
International Nuclear Information System (INIS)
Highlights: • Application of plastic heat exchangers in Organic Rankine Cycle module. • Low temperature heat recovery. • Design of a 20 kW regenerative ORC adopting commercial plastic heat exchangers. • Electricity cost comparable with ORC modules with typical carbon steel components. • Economic benefit from plastic evaporator adoption with corrosive heat source media. - Abstract: In this paper the possible replacement of conventional metallic heat exchangers with plastic components is investigated with reference to low size Organic Rankine Cycles, aiming at a reduction of the plant investment cost. A thermodynamic optimization of a 20 kW regenerative ORC plant, representative of a low temperature (<140 °C) heat recovery application, has been carried out according to the presently available data for plastic shell and tubes heat exchangers offered on the market. N-heptane was selected as the working fluid, thanks to the capability to operate within the pressure limits for evaporation and condensation processes imposed by the adoption of plastic components. Finally, the potential economic benefit of the plastic solution in comparison with conventional heat exchangers made of carbon steel was evaluated for the whole plant; the case of enhanced materials adoption, which is mandatory for the evaporator in presence of corrosive heat source media, was also considered. It turns out that advantages of the proposed solution become appreciable whenever the presence of corrosive heat source media requires the use of materials other than carbon steel. For instance, for a plant availability of 5000 h/year and discount rate of 10%, we obtain a cost of the produced electricity of 94.8 $/MW h, 95.4 $/MW h, 101.5 $/MW h, and 118.9 $/MW h respectively for plastic, carbon steel, stainless steel and titanium solutions
Compact interior heat exchangers for CO{sub 2} mobile heat pumping systems
Energy Technology Data Exchange (ETDEWEB)
Hafner, Armin
The natural refrigerant carbon dioxide (CO{sub 2}) offers new possibilities for design of flexible, efficient and environmentally safe mobile heat pumping systems. As high-efficient car engines with less waste heat are developed, extra heating of the passenger compartment is needed in the cold season. A reversible transcritical CO{sub 2} system with gliding temperature heat rejection can give high air delivery temperature which results in rapid heating of the passenger compartment and rapid defogging or defrosting of windows. When operated in cooling mode, the efficiency of transcritical CO{sub 2} systems is higher compared to common (HFC) air conditioning systems, at most dominant operating conditions. Several issues were identified for the design of compact interior heat exchangers for automotive reversible CO{sub 2} heat pumping systems. Among theses issues are: (1) Refrigerant flow distribution, (2) Heat exchanger fluid flow circuiting, (3) Air temperature uniformity downstream of the heat exchanger, (4) Minimization of temperature approach, (5) Windshield flash fogging due to retained water inside the heat exchanger, (6) Internal beat conduction in heating mode operation, and (7) Refrigerant side pressure drop In order to provide a basis for understanding these issues, the author developed a calculation model and set up a test facility and investigated different prototype heat exchangers experimentally.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Performance restoration technique developed for fouled heat exchanger
International Nuclear Information System (INIS)
Heat exchanger (HE) is one of the important equipments for satisfactory operation of installations like power plants, chemical plants, particle accelerators etc. The performance of HE depends on the material of construction (MOC) as well as good engineering practice adopted, and performance deterioration takes place due to surface deposition, making it a thermal insulator. In Indus Electron Synchrotron Accelerator, RRCAT, Plate Heat Exchangers (PHEs, heat exchangers having corrugated plates) are installed to dissipate heat from primary process coolant (deionised water) to secondary coolant (soft water) through parallel SS 316 corrugated plates. For achieving precise electron beam stability, the process cooling water temperature is maintained within ±1°C. Deposition of scale takes place in secondary coolant side as Saturation Index (SI) of cooling tower water is maintained at + 0.5 to have mild scale of calcium carbonate on pipeline and other wetted parts of the loop to prevent corrosion. This forms scale in HE and affects the heat transfer coefficient, requiring routine cleaning to remove scale of PHE to have designed performance. A hard and sticky scale was formed in PHE and the problem could not be addressed by standard reconditioning techniques available. Samples were systematically analysed in our laboratory to know the content of the deposit so that suitable method could be applied to remove the foulants to clean the HE. About 48.52 % of deposit was found to be acid soluble, whereas approximately 44.14% of deposit dissolves in alkali. The remaining residue (7.43%), neither dissolved in acid nor in alkali, may be mostly dust. The cleaning solution was formulated in-house to remove the scale from heat exchanger plates. Sulfamic acid solution at 80 °C was used to decompose calcium scale to liberate carbon dioxide, whereas sodium hydroxide solution was used to remove remaining scale. The performance of the heat exchangers was restored. The developed formulation
On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers
Energy Technology Data Exchange (ETDEWEB)
Garcia-Hernando, N.; de Vega, M. [Energy System Engineering (ISE), Departamento de Ingenieria Termica y de Fluidos, Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Leganes, Madrid (Spain); Almendros-Ibanez, J.A. [Escuela de Ingenieros Industriales de Albacete, Departamento de Mecanica Aplicada e Ingenieria de Proyectos, Universidad de Castilla La Mancha, Campus Universitario s/n, 02071 Albacete (Spain); Renewable Energy Research Institute, c/de la Investigacion s/n, 02071 Albacete (Spain); Ruiz, G. [Energy Efficiency and Renewables Department, Tecnicas Reunidas S.A., C/Arapiles No. 13, 10a, 28015 Madrid (Spain)
The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr-H{sub 2}O and NH{sub 3}-H{sub 2}O solutions is studied. For the NH{sub 3}-H{sub 2}O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr-H{sub 2}O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed. (author)
Plastic heat exchangers: a state-of-the-art review
Energy Technology Data Exchange (ETDEWEB)
Miller, D; Holtz, R E; Koopman, R N; Marciniak, T J; MacFarlane, D R
Significant increases in energy utilization efficiency can be achieved through the recovery of low-temperature rejected heat. This energy conserving possibility provides incentive for the development of heat exchangers which could be employed in applications where conventional units cannot be used. Some unique anticorrosion and nonstick characteristics of plastics make this material very attractive for heat recovery where condensation, especially sulfuric acid, and fouling occur. Some of the unique characteristics of plastics led to the commercial success of DuPont's heat exchangers utilizing polytetrafluoroethylene (trade name Teflon) tubes. Attributes which were exploited in this application were the extreme chemical inertness of the material and its flexibility, which enabled utilization in odd-shaped spaces. The wide variety of polymeric materials available ensures chemical inertness for almost any application. Lower cost, compoundability with fillers to improve thermal/mechanical properties, and versatile fabrication methods are incentives for many uses. Also, since many plastics resist corrosion, they can be employed in lower temperature applications (< 436 K), where condensation can occur and metal units have been unable to function. It is clear that if application and design can be merged to produce a cost-effective alternate to present methods of handling low-temperature rejected heat, then there is significant incentive for plastic heat exchangers, to replace traditional metallic heat exchangers or to be used in services where metals are totally unsuited.
Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger
Kuznetsov, V. V.; Shamirzaev, A. S.
The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.
On the use of hydration heat for quality management of borehole heat exchanger grouting
Suibert Oskar Seibertz, Klodwig; Händel, Falk; Dietrich, Peter; Vienken, Thomas
The ongoing energy transition from conventional, fossil fuel based energy generation, over to renewable energy sources led to an increase in geothermal energy use. Different systems for extracting heat from the subsurface are in use, whereas a commonly used system is the borehole heat exchanger (BHE). A BHE generally consist of a closed loop pipe system through which a heat exchanging fluid is circulated. The BHE is surrounded by grouting. The grouting, focus of this work, has two main objectives to fulfill: Firstly, to thermally couple the subsurface and the BHE pipes; and, secondly, to protect the pipes and to prevent the heat exchanging fluid from entering the subsurface in case of BHE mechanical failure. Therefore, to provide proper functionality, efficiency, and safety of a BHE, it has to be guaranteed that the grouting does not have defects. The hardening reaction (hydration) of the grouting is exothermic, whereas the grouting is mostly a variant of (thermally enhanced) cement. The hydration temperature depends on the type of grout as well as the possible dilutions (resulting in defects) of the grouting material by water, air or drilling debris, and the thermal transport potential of the subsurface. Therefore the quality of the grouting can be investigated by temperature measurements during the hardening process. To validate this further, tests on field and laboratory scale were conducted. For laboratory testing, different columns were built in which different defects of BHE grouting and pipes were simulated. For defect simulation isolation and mixing with drilling debris were chosen, representing inclusions of water and/or air during cement casting as well as partial collapse of the borehole. The temperature changes during installation and hardening of the grouting are measured by fiber-optic distributed temperature sensing (DTS). This allows for temporal and spatial high resolution, continuous temperature measurements at the interface of pipe to grout
Retrofitting of heat exchanger networks involving streams with variable heat capacity: Application of single and multi-objective optimization
International Nuclear Information System (INIS)
Heat exchanger network (HEN) retrofitting improves the energy efficiency of the current process by reducing external utilities. In this work, HEN retrofitting involving streams having variable heat capacity is studied. For this, enthalpy values of a stream are fitted to a continuous cubic polynomial instead of a stepwise approach employed in the previous studies [1,2]. The former methodology is closer to reality as enthalpy or heat capacity changes gradually instead of step changes. Using the polynomial fitting formulation, single objective optimization (SOO) and multi-objective optimization (MOO) of a HEN retrofit problem are investigated. The results obtained show an improvement in the utility savings, and MOO provides many Pareto-optimal solutions to choose from. Also, Pareto-optimal solutions involving area addition in existing heat exchangers only (but no new exchangers and no structural modifications) are found and provided for comparison with those involving new exchangers and structural modifications as well. - Highlights: • HEN retrofitting involving streams with variable heat capacities is studied. • A continuous approach to handle variable heat capacity is proposed and tested. • Better and practical solutions are obtained for HEN retrofitting in process plants. • Pareto-optimal solutions provide many alternate choices for HEN retrofitting
Intensification of heat and mass transfer by ultrasound: application to heat exchangers and membrane separation processes.
Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E
This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions.
Flow mechanism and heat transfer enhancement in longitudinal-flow tube bundle of shell-and-tube heat exchanger
Institute of Scientific and Technical Information of China (English)
The flow disturbance and heat transfer mechanism in the tube bundle of rod baffle shell-and-tube heat exchanger were analyzed, on the basis of which and combined with the concept of heat transfer enhancement in the core flow, a new type of shell-and-tube heat exchanger with combination of rod and van type spoiler was designed. Corresponding mathematical and physical models on the shell side about the new type heat exchanger were established, and fluid flow and heat transfer characteristics were numerically analyzed. The simulation results showed that heat transfer coefficient of the new type of heat exchanger approximated to that of rod baffle heat exchanger, but flow pressure drop was much less than the latter, indicating that comprehensive performance of the former is superior to that of the latter. Compared with rod baffle heat exchanger, heat transfer coefficient of the heat exchanger under investigation is higher under same pressure drop, especially under the high Reynolds numbers.
Simulated heat-exchanger tubes: DOE Geothermal Test Facility, East Mesa, California
Ellis, P. F., II; Anliker, D. M.
A 103 hr corrosion test was performed of two geothermal heat exchanger materials, Allegheny-Ludlum Alloy 29-4 and Alloy 29-4C. Coupons of the two metals were exposed under conditions simulating flow in a geothermal heat exchanger tube. Continuous flow and cyclic exposure tests were made. No signs of localized corrosion were observed in either the base metal, tube weld seam, or heat affected zone. Most coupons show statistically insignificant weight change. A corrosion rate of less than 0.5 mil/yr is indicated. No significant difference in the performance of the two alloys is reported.
Liquid Salt Heat Exchanger Technology for VHTR Based Applications
Energy Technology Data Exchange (ETDEWEB)
Anderson, Mark; Sridhara, Kumar; Allen, Todd; Peterson, Per
The objective of this research is to evaluate performance of liquid salt fluids for use as a heat carrier for transferring high-temperature process heat from the very high-temperature reactor (VHTR) to chemical process plants. Currently, helium is being considered as the heat transfer fluid; however, the tube size requirements and the power associated with pumping helium may not be economical. Recent work on liquid salts has shown tremendous potential to transport high-temperature heat efficiently at low pressures over long distances. This project has two broad objectives: To investigate the compatibility of Incoloy 617 and coated and uncoated SiC ceramic composite with MgCl2-KCl molten salt to determine component lifetimes and aid in the design of heat exchangers and piping; and, To conduct the necessary research on the development of metallic and ceramic heat exchangers, which are needed for both the helium-to-salt side and salt-to-process side, with the goal of making these heat exchangers technologically viable. The research will consist of three separate tasks. The first task deals with material compatibility issues with liquid salt and the development of techniques for on-line measurement of corrosion products, which can be used to measure material loss in heat exchangers. Researchers will examine static corrosion of candidate materials in specific high-temperature heat transfer salt systems and develop an in situ electrochemical probe to measure metallic species concentrations dissolved in the liquid salt. The second task deals with the design of both the intermediate and process side heat exchanger systems. Researchers will optimize heat exchanger design and study issues related to corrosion, fabrication, and thermal stresses using commercial and in-house codes. The third task focuses integral testing of flowing liquid salts in a heat transfer/materials loop to determine potential issues of using the salts and to capture realistic behavior of the salts in a
CFD analysis of the plate heat exchanger - Mathematical modelling of mass and heat transfer in serial connection with tubular heat exchanger
Bojko, Marian; Kocich, Radim
Application of numerical simulations based on the CFD calculation when the mass and heat transfer between the fluid flows is essential component of thermal calculation. In this article the mathematical model of the heat exchanger is defined, which is subsequently applied to the plate heat exchanger, which is connected in series with the other heat exchanger (tubular heat exchanger). The present contribution deals with the possibility to use the waste heat of the flue gas produced by small micro turbine. Inlet boundary conditions to the mathematical model of the plate heat exchanger are obtained from the results of numerical simulation of the tubular heat exchanger. Required parameters such for example inlet temperature was evaluated from temperature field, which was subsequently imported to the inlet boundary condition to the simulation of plate heat exchanger. From the results of 3D numerical simulations are evaluated basic flow variables including the evaluation of dimensionless parameters such as Colburn j-factor and friction ft factor. Numerical simulation is realized by software ANSYS Fluent15.0.
Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers
Directory of Open Access Journals (Sweden)
Hanuszkiewicz-Drapała Małgorzata
Full Text Available A cross-flow, tube and fin heat exchanger of the water – air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.
Numerical evaluation of plate heat exchanger performance in geothermal district heating systems
Energy Technology Data Exchange (ETDEWEB)
Karlsson, T. [Iceland Univ., Reykjavik (Iceland)
This paper describes the performance of plate heat exchangers in residential water radiator heating systems receiving their heat from geothermal resources. Radiator theory is reviewed and determination of annual hot water requirements for space heating is discussed. Performance evaluation is made of plate heat exchangers and results obtained by means of two equations commonly used for this purpose, the Sieder-Tate and the Dittus-Boelter equations, compared to results obtained with a simplified equation where heat transfer in the heat exchanger is assumed to depend only on the fluid mass flow on both sides. It is found that for prevailing temperature ranges in Icelandic geothermal systems the mass pow approximation gives results very close to those determined by the more complicated conventional equations. (UK)
Active heat exchange system development for latent heat thermal energy storage
Alario, J.; Haslett, R.
Various active heat exchange concepts were identified from among three generic categories: scrapers, agitators/vibrators and slurries. The more practical ones were given a more detailed technical evaluation and an economic comparison with a passive tube-shell design for a reference application. Two concepts selected for hardware development are a direct contact heat exchanger in which molten salt droplets are injected into a cooler counterflowing stream of liquid metal carrier fluid, and a rotating drum scraper in which molten salt is sprayed onto the circumference of a rotating drum, which contains the fluid heat sink in an internal annulus near the surface. A fixed scraper blade removes the solidified salt from the surface which has been nickel plated to decrease adhesion forces. Suitable phase change material (PCM) storage media with melting points in the temperature range of interest (250 C to 400 C) were investigated. The specific salt recommended for laboratory tests was a chloride eutectic (20.5KCl-24/5 NaCl-55.0MgCl 2% by wt.), with a nominal melting point of 385 C.
Air-side Particulate Fouling of Microchannel Heat Exchangers: Experimental Comparison of Air-Side Pressure Drop and Heat Transfer with Plate-Fin Heat Exchanger
Bell, Ian; Groll, Eckhard
In this study, the air-side pressure drop and heat transfer performance of plate-fin and microchannel coils were tested under clean and fouled conditions. The heat exchangers were tested with two different types of dust, ASHRAE Standard Dust and Arizona Road Test Dust. The ASHRAE Standard Dust was found to have a very significant impact on the pressure drop of the microchannel heat exchanger, increasing the air-side pressure drop of the microchannel heat exchanger over 200% for a dust injec...
Nanorod near-field radiative heat exchange analysis
International Nuclear Information System (INIS)
A theoretical method for cylinder-to-cylinder radiative heat exchange is formulated. The method utilized was a modified version of a previously published numerical method for near-field sphere-to-sphere radiative exchange. Modifications were made to the numerical procedure to make it applicable to cylindrical geometry of nanorods. Nanorods investigated had length to diameter ratios of 3:1 and 7:1. The heat exchange of nanorods is plotted vs. gap to assess the impact of near-field radiative transfer as gap decreases. Graphical results of energy vs. nanorod radii are also presented. A nanorod-to-plane configuration is estimated utilizing a nanorod asymptotic method. The nanorod-to-nanorod method approximates a nanorod-to-plane geometric configuration when one nanorod radii is held constant, and the second nanorod radii is iteratively increased until the corresponding radiative exchange converges.
Thermal behavior of a heat exchanger module for seasonal heat storage
DEFF Research Database (Denmark)
Fan, Jianhua; Furbo, Simon; Andersen, Elsa;
are theoretically investigated by Computational Fluid Dynamics (CFD) calculations. The heat transfer rates between the PCM storage and the heating fluid/cooling fluid in the plate heat exchangers are determined. The CFD calculated temperatures are compared to measured temperatures. Based on the studies...
A prototype heat pipe heat exchanger for the capillary pumped loop flight experiment
Ku, Jentung; Yun, Seokgeun; Kroliczek, Edward J.
A Capillary Pumped Two-Phase Heat Transport Loop (CAPL) Flight Experiment, currently planned for 1993, will provide microgravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. CAPL employs a heat pipe heat exchanger (HPHX) to couple the condenser section of the CPL to the radiator assembly. A prototype HPHX consisting of a heat exchanger (HX), a header heat pipe (HHP), a spreader heat pipe (SHP), and a flow regulator has been designed and tested. The HX transmits heat from the CPL condenser to the HHP, while the HHP and SHP transport heat to the radiator assembly. The flow regulator controls flow distribution among multiple parallel HPHX's. Test results indicated that the prototype HPHX could transport up to 800 watts with an overall heat transfer coefficient of more than 6000 watts/sq m-deg C. Flow regulation among parallel HPHX's was also demonstrated.
Dynamic tube/support interaction in heat exchanger tubes
Energy Technology Data Exchange (ETDEWEB)
Chen, S.S.
The supports for heat exchanger tubes are usually plates with drilled holes; other types of supports also have been used. To facilitate manufacture and to allow for thermal expansion of the tubes, small clearances are used between tubes and tube supports. The dynamics of tube/support interaction in heat exchangers is fairly complicated. Understanding tube dynamics and its effects is important for heat exchangers. This paper summarizes the current state of the art on this subject and to identify future research needs. Specifically, the following topics are discussed: dynamics of loosely supported tubes, tube/support gap dynamics, tube response in flow, tube damage and wear, design considerations, and future research needs. 55 refs., 1 fig.
Mill Scale Corrosion and Prevention in Carbon Steel Heat Exchanger
Sharma, Pankaj; Roy, Himadri
The cause of material degradation of an ASTM A-124 grade carbon steel tube belonging to a heat exchanger has been investigated. Visual examination, followed by an in-depth microstructural characterization using optical microscopy, energy dispersive X-ray, and scanning electron microscopy, was carried out for understanding the primary cause of material degradation. Based on the results of an extensive examination as well as the background information provided on the heat exchanger, it was determined that the steel tubes were predominantly damaged by the mechanism of crevice corrosion facilitated by the presence of mill scale. It is concluded that the heat exchanger tubes were not properly investigated for defects after their fabrication. Based on the situation, the proper cleaning method was selected for preventing further corrosion in the system. A chemical cleaning process was designed using acid pickling along with an inhibitor and a surfactant.
Heat exchanger analysis on a Microvax II/GPX
Haught, Alan F.
The finite element code FIDAP was used to examine the fluid flow path within a flat plate tube/fin heat exchanger and the resulting heat transfer from the fins and tube walls. The mathematical formulation, mesh development and analysis procedure are presented, and the results obtained are compared with experimental observations of the fluid flow and measurements of the fluid heating. This problem illustrates the capabilities of finite element techniques for analyzing complex three-dimensional convection-dominated heat transfer, and demonstrates the scope of problems which can be addressed on a Micro VAX II/GPX workstation.
Diffusion Welding of Compact Heat Exchangers for Nuclear Applications
Energy Technology Data Exchange (ETDEWEB)
Denis Clark; Ron Mizia; Dr. Michael V. Glazoff; Mr. Michael W. Patterson
The next--generation nuclear plant (NGNP) is designed to be a flexible source of energy, producing various mixes of electrical energy and process heat (for example, for hydrogen generation) on demand. Compact heat exchangers provide an attractive way to move energy from the helium primary reactor coolant to process heat uses. For process heat efficiency, reactor outlet temperatures of 750--900°C are desirable. There are minor but deleterious components in the primary coolant; the number of alloys that can handle this environment is small. The present work concentrates on Alloys 800H and 617.
Efficiency of Vertical Geothermal Heat Exchangers in the Ground Source Heat Pump System
Institute of Scientific and Technical Information of China (English)
Heyi Zeng; Nairen Diao; Zhaohong Fang
Taking the fluid temperature distribution along the borehole depth into account, a new quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchangers. On this basis the efficiency of the borehole has been defined and its analytical expression derived. Comparison with the previous two-dimensional model shows that the quasi-three-dimensional model is more rational and more accurate to depict the practical feature of the conduction of geothermal heat exchanger, and the efficiency notion can be easily used to determine the inlet and outlet temperature of the circulating fluid inside the heat exchanger.
Comparative design evaluation of plate fin heat exchanger and coiled finned tube heat exchanger for helium liquefier in the temperature range of 300-80 K
International Nuclear Information System (INIS)
Present indigenous helium liquefaction system at RRCAT uses the cross-counter flow coiled-finned tube heat exchangers developed completely from Indian resources. These coiled-finned tube heat exchangers are mainly suitable up to medium capacity helium liquefiers. For large capacity helium liquefier, plate fin heat exchangers are more suitable options. This paper presents the comparative evaluation of the design of both types of heat exchangers in the temperature range of 300-80 K for helium liquefier. (author)
Numerical Study of Condensation Heat Exchanger Design in a Saturated Pool: Correlation Investigation
Energy Technology Data Exchange (ETDEWEB)
Lee, Hee Joon [Kookmin University, Seoul (Korea, Republic of); Lee, Tae Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
Generally the condensation heat exchanger has higher heat transfer coefficient compared to the single phase heat exchanger, so has been widely applied to the cooling systems of fissile power plant. Recently vertical or horizontal type condensation heat exchangers are being studied for the application to secondary passive cooling system of nuclear plants. To design vertical condensation heat exchanger in a saturated water pool, a thermal sizing program of condensation heat exchanger, TSCON(Thermal Sizing of CONdenser) was developed. In this study, condensing heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without noncondensable gas effect (pure steam condensation)
Development of User-Friendly Software to Design Dairy Heat Exchanger and Performance Evaluation
Directory of Open Access Journals (Sweden)
Full Text Available The paper proposes a calculation algorithm and development of a software in Visual Basic(Visual Studio 2012 Express Desktop used in heat transfer studies when different heat exchangers are involved (e.g. Helical Type Triple Tube Heat Exchanger , Plate Type Heat Exchanger.It includes the easy calculation of heat transfer coefficient and followed by the design and simulation of heat exchanger design parameter by inputting general known parameters of a heat exchanger into the developed software—-―DAIRY –HE ―. A parametric study is conducted using the software interface to determine the length of tubes or dimensions of heat exchanger.
Performance of a Thermoelectric Device with Integrated Heat Exchangers
Barry, Matthew M.; Agbim, Kenechi A.; Chyu, Minking K.
Thermoelectric devices (TEDs) convert heat directly into electrical energy, making them well suited for waste heat recovery applications. An integrated thermoelectric device (iTED) is a restructured TED that allows more heat to enter the p-n junctions, thus producing a greater power output . An iTED has heat exchangers incorporated into the hot-side interconnectors with flow channels directing the working fluid through the heat exchangers. The iTED was constructed of p- and n-type bismuth-telluride semiconductors and copper interconnectors and rectangular heat exchangers. The performance of the iTED in terms of , produced voltage and current , heat input and conversion efficiency for various flow rates (), inlet temperatures (C) ) and load resistances () with a constant cold-side temperature ( = 0C) was conducted experimentally. An increase in had a greater effect on the performance than did an increase in . A 3-fold increase in resulted in a 3.2-, 3.1-, 9.7-, 3.5- and 2.8-fold increase in and respectively. For a constant of 50C, a 3-fold increase in from 3300 to 9920 resulted in 1.6-, 1.6-, 2.6-, 1.5- and 1.9-fold increases in , , , and respectively.
В.О. Когут; В.В. Мінєнков; М.Г. Хмельнюк
This paper describes the use of a heat-exchanger ejector device for air humidification in a refrigeration treatment camera of meat half-carcasses, and the possibility of its application for artificial snow. The system of a two-step meat moistening in the isolated compartment by treating meat with a mixture of cooled air and the fine crystal ice particles is represented in this article. The design scheme and the principle of the heat exchanger ejector is shown. The ice crystals formed at the o...
Performance of a liquid flow ultra-compact heat exchanger
Sammataro, Michael A.
A numerical analysis of the performance of compact pin-fin array heat exchangers was carried out using water and JP-4 fuel as the working fluids. Three different configurations were used with hydraulic diameters ranging from 0.137 to 0.777 mm, and volumetric area densities varying between 4.5 and 14.5 mm2/mm3. Numerical simulations were carried out to determine the performance of each heat exchanger over a series of Reynolds numbers in both the laminar and turbulent flow regimes. It was found...
Heat exchange equipment for the Sizewell 'B' turbine generators
International Nuclear Information System (INIS)
The Heat Exchange Equipment associated with the Sizewell 'B' Turbine Generators embodies features specific to the wet steam cycle of the PWR. In comparison with fossil fuelled plant, steam conditions are considerably lower and so for a given electrical output, steam and feed water flows are of necessity much higher. In addition, the plant must embody measures to combat wet steam erosion and to accommodate substantial quantities of draining separated condensate. The paper describes key features of design, layout and materials selection on the Sizewell 'B' heat exchange equipment which address these problems. (author)
Internal dust recirculation system for a fluidized bed heat exchanger
Gamble, Robert L.; Garcia-Mallol, Juan A.
A fluidized bed heat exchanger in which air is passed through a bed of particulate material containing fuel disposed in a housing. A steam/water natural circulation system is provided in a heat exchange relation to the bed and includes a steam drum disposed adjacent the bed and a tube bank extending between the steam drum and a water drum. The tube bank is located in the path of the effluent gases exiting from the bed and a baffle system is provided to separate the solid particulate matter from the effluent gases. The particulate matter is collected and injected back into the fluidized bed.
Multiphysics Numerical Modeling of a Fin and Tube Heat Exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM). For the ......In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM...
Simulation on Thermal Integrity of the Fin/Tube Brazed Joint of Heat Exchangers
Institute of Scientific and Technical Information of China (English)
Yiyu QIAN; Feng GAO; Fengjiang WANG; Hui ZHAO
In the applications of heat exchangers, the fin efficiency of heat transfer is the key issue. Thermal distribution withinthe brazed joints in heat exchanger under loading conditions is investigated in this paper. Simulated results showedthat the therma
Experimental investigation of a reticulated porous alumina heat exchanger for high temperature gas heat recovery
International Nuclear Information System (INIS)
The present study presents an experimental study of a prototype counter-flow heat exchanger designed to recover sensible heat from inert and reactive gases flowing through a high temperature solar reactor for splitting CO2. The tube-in-tube heat exchanger is comprised of two concentric alumina tubes, each filled with reticulated porous alumina with a nominal porosity of 80% and pore density of 5 pores per inch (ppi). The RPC provides high heat transfer surface area per unit volume (917 m−1) with low pressure drop. Measurements include the permeability, inertial coefficient, overall heat transfer coefficient, effectiveness and pressure drop. For laminar flow and an inlet gas temperature of 1240 K, the overall heat transfer coefficients are 36–41 W m−2 K−1. The measured performance is in good agreement with a prior CFD model of the heat exchanger. - Highlights: • A ceramic heat exchanger provides gas-phase heat recuperation for a solar thermochemical reactor. • Alumina reticulated porous ceramic (RPC) provides high surface area and low pressure drop. • Heat transfer and pressure drop are measured at temperatures up to 1240 K. • RPC provides a 9-fold increase in heat transfer compared to bare tubes
Fuel type impact at heat exchanger performance
Durčanský, Peter; Patsch, Marek; Jandačka, Jozef
Possible solution to the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration in combination with increasing energy effectiveness. The use of renewable sources, such as biomass, represents an important contribution to possible solution of this problem. When designing a new heat source it is required to follow a number of technical regulations and recommendations. The proposed combustion furnace is intended for combustion of biomass, either piece, or in the form of wood biomass. But the combustion is not only affected by design of furnace, but also by fuel and its properties.
Optimization of the Heat Exchangers of a Thermoelectric Generation System
Martínez, A.; Vián, J. G.; Astrain, D.; Rodríguez, A.; Berrio, I.
The thermal resistances of the heat exchangers have a strong influence on the electric power produced by a thermoelectric generator. In this work, the heat exchangers of a thermoelectric generator have been optimized in order to maximize the electric power generated. This thermoelectric generator harnesses heat from the exhaust gas of a domestic gas boiler. Statistical design of experiments was used to assess the influence of five factors on both the electric power generated and the pressure drop in the chimney: height of the generator, number of modules per meter of generator height, length of the fins of the hot-side heat exchanger (HSHE), length of the gap between fins of the HSHE, and base thickness of the HSHE. The electric power has been calculated using a computational model, whereas Fluent computational fluid dynamics (CFD) has been used to obtain the thermal resistances of the heat exchangers and the pressure drop. Finally, the thermoelectric generator has been optimized, taking into account the restrictions on the pressure drop.
Directory of Open Access Journals (Sweden)
María Fernanda Laborde
Full Text Available With the objective to aboard one of the challenges in Engineering teaching: It´s the application in professional practice?, along with attending to the actual requirements of achieve energetic efficiency in industrial process and to reuse wastes of food industry, this work, presents the application of heat exchange networks for the resolution of a real case: pre-treatment of waste cooking oils (WCO withacid catalysis for biodiesel production. Different methods and software are applied to obtain the minimum amounts of heat and the heat exchange network for a processing capacity of 0,19 kg/s of WCO. A minimum temperature difference (Tmin of 10°C is considered and the minimum requirements of heating and cooling result 4629,87 W and 10066,30 W, respectively. If this exchange network is not considered, this values increase to 26838,33 W and 21958,33 W, respectively. Applying heat exchange network, decrease 78,92% the required steam service in the process and water cooling service decreases 62,48%, demonstrating that integration reduces energetic requirements respect the non-integrated process.
Heat exchanger identification by using iterative fuzzy observers
Lalot, Sylvain; Guðmundsson, Oddgeir; Pálsson, Halldór; Pálsson, Ólafur Pétur
The principle of fuzzy observers is first illustrated on a general example: the determination of the two parameters of second order systems using a step response. The set of equations describing the system are presented and it is shown that accurate results are obtained, even for a high level of noise. The heat exchanger model is then introduced. It is based on a spatial division of a counter flow heat exchanger into multiple sections. The governing equations are rewritten as a state space representation. The number of sections needed to get accurate results is determined by comparing estimated values to experimental data. Based on the mean value of the root mean squared errors, it is shown that 80 sections is an appropriate value for this heat exchanger. It is then shown that the iterative fuzzy observers can be used to determine the main parameters of the counter flow heat exchanger, i.e. the convection heat transfer coefficients, when in transient state. The final values of these parameters are steady state.
Fouling detection in heat exchangers by Takagi-Sugeno observers
International Nuclear Information System (INIS)
The phenomenon of fouling in heat exchangers is currently an important topic. Indeed, the fouling is a costly issue that increases the energy loss (directly or indirectly through an over-sizing of the equipment), and therefore increases the water consumption. As a side effect, fouling increases CO2 consumption that leads to environmental consequences. Fouling can be detected either on local scale, using expensive and specific sensors or on global scale. Global estimation of fouling can be done by measuring the variation of the mass of the exchanger, or by estimating the efficiency of the exchanger through the transfer coefficient. These two methods require very restricting conditions: a powered exchanger to measure mass variation and a steady state exchanger to estimate the efficiency. The work introduced in this thesis deals with the development of non-linear observers that detect fouling early enough to start an efficient cleaning process. As a beginning, a finite element model of a counter current tubular exchanger was proposed. Then three approaches, based on non-linear Takagi-Sugeno observers, were suggested to detect early fouling in heat exchangers. First approach consisted in a set of observers that estimated the parameters of fouling effect through an interpolation method. The second approach proposed a polynomial Takagi-Sugeno observer, using the theory of sums of squares. Finally, a observer of Takagi-Sugeno type with unknown inputs was developed. As a conclusion, a comparison between those different methods was done. (author)
Characterization of a mini-channel heat exchanger for a heat pump system
International Nuclear Information System (INIS)
In this paper a mini-channel aluminum heat exchanger used in a reversible heat pump is presented. Mini-channel finned heat exchangers are getting more and more interest for refrigeration systems, especially when compactness and low refrigerant charge are desired. Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator in terms of heat transfer performance and to study the refrigerant distribution in the manifold. The heat exchanger characterization was performed experimentally by means of a test rig built up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and internal air circulation arranged in a closed loop, measurement sensors and an acquisition system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the present design and to identify possible solutions for the future improvement of the manifold design.
The influence of a radiated heat exchanger surface on heat transfer
Directory of Open Access Journals (Sweden)
Morel Sławomir
Full Text Available The experiment leads to establish the influence of radiated surface development heat exchangers on the values of heat flux transferred with water flowing through the exchangers and placed in electric furnace chamber. The values of emissivity coefficients are given for the investigated metal and ceramic coatings. Analytical calculations have been made for the effect of the heating medium (flame – uncoated wall and then heating medium (flame – coated wall reciprocal emissivity coefficients. Analysis of the values of exchanged heat flux were also realized. Based on the measurement results for the base coating properties, these most suitable for spraying the walls of furnaces and heat exchangers were selected, and determined by the intensification of heat exchange effect. These coatings were used to spray the walls of a laboratory waste-heat boiler, and then measurements of fluxes of heat absorbed by the cooling water flowing through the boiler tubes covered with different type coatings were made. Laboratory tests and calculations were also confirmed by the results of full-scale operation on the metallurgical equipment.
Ground Source Heat Pump Sub-Slab Heat Exchange Loop Performance in a Cold Climate
Energy Technology Data Exchange (ETDEWEB)
Mittereder, N.; Poerschke, A.
This report presents a cold-climate project that examines an alternative approach to ground source heat pump (GSHP) ground loop design. The innovative ground loop design is an attempt to reduce the installed cost of the ground loop heat exchange portion of the system by containing the entire ground loop within the excavated location beneath the basement slab. Prior to the installation and operation of the sub-slab heat exchanger, energy modeling using TRNSYS software and concurrent design efforts were performed to determine the size and orientation of the system. One key parameter in the design is the installation of the GSHP in a low-load home, which considerably reduces the needed capacity of the ground loop heat exchanger. This report analyzes data from two cooling seasons and one heating season. Upon completion of the monitoring phase, measurements revealed that the initial TRNSYS simulated horizontal sub-slab ground loop heat exchanger fluid temperatures and heat transfer rates differed from the measured values. To determine the cause of this discrepancy, an updated model was developed utilizing a new TRNSYS subroutine for simulating sub-slab heat exchangers. Measurements of fluid temperature, soil temperature, and heat transfer were used to validate the updated model.
Characterization of a mini-channel heat exchanger for a heat pump system
Arteconi, A.; Giuliani, G.; Tartuferi, M.; Polonara, F.
In this paper a mini-channel aluminum heat exchanger used in a reversible heat pump is presented. Mini-channel finned heat exchangers are getting more and more interest for refrigeration systems, especially when compactness and low refrigerant charge are desired. Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator in terms of heat transfer performance and to study the refrigerant distribution in the manifold. The heat exchanger characterization was performed experimentally by means of a test rig built up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and internal air circulation arranged in a closed loop, measurement sensors and an acquisition system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the present design and to identify possible solutions for the future improvement of the manifold design.
The influence of a radiated heat exchanger surface on heat transfer
Morel, Sławomir
The experiment leads to establish the influence of radiated surface development heat exchangers on the values of heat flux transferred with water flowing through the exchangers and placed in electric furnace chamber. The values of emissivity coefficients are given for the investigated metal and ceramic coatings. Analytical calculations have been made for the effect of the heating medium (flame) - uncoated wall and then heating medium (flame) - coated wall reciprocal emissivity coefficients. Analysis of the values of exchanged heat flux were also realized. Based on the measurement results for the base coating properties, these most suitable for spraying the walls of furnaces and heat exchangers were selected, and determined by the intensification of heat exchange effect. These coatings were used to spray the walls of a laboratory waste-heat boiler, and then measurements of fluxes of heat absorbed by the cooling water flowing through the boiler tubes covered with different type coatings were made. Laboratory tests and calculations were also confirmed by the results of full-scale operation on the metallurgical equipment.
Computer aided optimal design of heat exchanger networks
International Nuclear Information System (INIS)
A method for finding the best (optimal) operating layout of heat exchangers in complicated thermal networks is developed in this paper. Computer algorithms are developed that take advantage of pinch technology and economic considerations, and exergetic constraints as well as conventional heat and mass balances. The authors goals were to achieve minimum loss of exergy between hot and cold streams subject to practical system constraints. Furthermore, resulting networks should be limited to no more units than the theoretical minimum. The ultimate goal was to minimize investment and operating costs for a set of fixed overall system constraints. The influence of the minimum temperature difference on capital cost, heat transfer area, exergetic losses and second law efficiency of various heat exchangers in the network is presented
Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger
Ungar, Eugene K.; Schunk, Richard G.
An active thermal control system architecture has been modified to include a regenerative heat exchanger (regenerator) inboard of the radiator. Rather than using a radiator bypass valve a regenerative heat exchanger is placed inboard of the radiators. A regenerator cold side bypass valve is used to set the return temperature. During operation, the regenerator bypass flow is varied, mixing cold radiator return fluid and warm regenerator outlet fluid to maintain the system setpoint. At the lowest heat load for stable operation, the bypass flow is closed off, sending all of the flow through the regenerator. This lowers the radiator inlet temperature well below the system set-point while maintaining full flow through the radiators. By using a regenerator bypass flow control to maintain system setpoint, the required minimum heat load to avoid radiator freezing can be reduced by more than half compared to a radiator bypass system.
Numerical simulation of heat exchangers elliptical tubes and corrugated fins
International Nuclear Information System (INIS)
The intensified heat exchangers fins are widely used in the automotive and domestic industry. The low heat transfer coefficients on the air side are the main reason why these fins of heat exchangers need to be intensified. In this paper, the numerical simulation of a wavy fin type is made with elliptical tubes. The dimensions of the fin is in the range of those used in air conditioning equipment. The friction factor and the mass transfer coefficient as a function of the Reynolds number for this type of fin, always within the laminar regime is determined. The numerical model against experimental results published in the literature is validated. In addition the mechanisms that produce intensified heat transfer fin in such occur. (full text)
Intensification of heat transfer between heat exchange surfaces at low RE values
Directory of Open Access Journals (Sweden)
Cernecky Jozef
Full Text Available This contribution deals with the heat transfer parameters and pressure losses in heat exchange sets with six geometrical arrangements at low Re values (Re from 476 to 2926. Geometrical arrangements were characterised by the h/H ratio ranging from 0.2 to 1.0. The experiments used the holographic interferometry method in real time. This method enables visible and quantitative evaluations of images of temperature fields in the examined heat exchange. These images are used to determine the local and mean heat transfer parameters. The obtained data were used to determine the Colburn j-factor and the friction coefficient f. The measured values show that by using the profiled heat exchange surfaces and inserting regulating tubes, an intensification of heat transfer (increase of Num, and/or j was achieved. However, pressure losses recorded a significant increase (increase of f.
Effect of Corrugation Angle on Heat Transfer Studies of Viscous Fluids in Corrugated Plate Heat Exchangers
Directory of Open Access Journals (Sweden)
B Sreedhara Rao
Full Text Available In the present investigation heat transfer studies are conducted in corrugated plate heat exchangers (PHEs having three different corrugation angles of 300, 400 and 500. The plate heat exchangers have a length of 30 cm and a width of 10 cm with a spacing of 5 mm. Water and 20% glycerol solution are taken as test fluids and hot fluid is considered as heating medium. The wall temperatures are measured along the length of exchanger at seven different locations by means of thermocouples. The inlet and outlet temperatures of test fluid and hot fluid are measured by means of four more thermocouples. The experiments are conducted at a flowrate ranging from 0.5 lpm to 6 lpm with the test fluid. Film heat transfer coefficient and Nusselt number are determined from the experimental data. These values are compared with different corrugation angles. The effects of corrugation angles on heat transfer rates are discussed.
ASME code considerations for the compact heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Nestell, James [MPR Associates Inc., Alexandria, VA (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
The mission of the U.S. Department of Energy (DOE), Office of Nuclear Energy is to advance nuclear power in order to meet the nation's energy, environmental, and energy security needs. Advanced high temperature reactor systems such as sodium fast reactors and high and very high temperature gas-cooled reactors are being considered for the next generation of nuclear reactor plant designs. The coolants for these high temperature reactor systems include liquid sodium and helium gas. Supercritical carbon dioxide (sCO₂), a fluid at a temperature and pressure above the supercritical point of CO₂, is currently being investigated by DOE as a working fluid for a nuclear or fossil-heated recompression closed Brayton cycle energy conversion system that operates at 550°C (1022°F) at 200 bar (2900 psi). Higher operating temperatures are envisioned in future developments. All of these design concepts require a highly effective heat exchanger that transfers heat from the nuclear or chemical reactor to the chemical process fluid or the to the power cycle. In the nuclear designs described above, heat is transferred from the primary to the secondary loop via an intermediate heat exchanger (IHX) and then from the intermediate loop to either a working process or a power cycle via a secondary heat exchanger (SHX). The IHX is a component in the primary coolant loop which will be classified as "safety related." The intermediate loop will likely be classified as "not safety related but important to safety." These safety classifications have a direct bearing on heat exchanger design approaches for the IHX and SHX. The very high temperatures being considered for the VHTR will require the use of very high temperature alloys for the IHX and SHX. Material cost considerations alone will dictate that the IHX and SHX be highly effective; that is, provide high heat transfer area in a small volume. This feature must be accompanied by low pressure drop and mechanical reliability and
Heat transfer in borehole heat exchangers and the contribution of groundwater flow
Liuzzo Scorpo, Alberto
The exploitation of geothermal heat by ground source heat pumps is presently growing throughout Europe and the world. In Italy, at the end of 2010, borehole heat exchangers covered most of the 30% of the total energy used for space conditioning, showing an increase of 50%compared to 2005. The forecasts for 2015 suggest a further increase in the direct uses of the geothermal heat exceeding 50% compared to 2010 and a corresponding increase in the geothermal energy consumption. The possibilit...
Double tube heat exchanger with novel enhancement: Part II - single phase convective heat transfer
Energy Technology Data Exchange (ETDEWEB)
Tiruselvam, R.; Chin, W.M.; Raghavan, Vijay R. [OYL Sdn. Bhd., Research and Application Department, Kuala Lumpur (Malaysia)
The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction. (orig.)
A heat exchanger analogy of automotive paint ovens
International Nuclear Information System (INIS)
Computational prediction of vehicle temperatures in an automotive paint oven is essential to predict paint quality and manufacturability. The complex geometry of vehicles, varying scales in the flow, transient nature of the process, and the tightly coupled conjugate heat transfer render the numerical models computationally very expensive. Here, a novel, simplified model of the oven is developed using an analogy to a three-stream cross flow heat exchanger that transfers heat from air to a series of moving bodies and supporting carriers. The analogous heat exchanger equations are developed and solved numerically. Steady state Computational Fluid Dynamics (CFD) simulations are carried out to model the flow field and to extract the heat transfer coefficients around the body and carriers. The air temperature distribution from the CFD models is used as a boundary condition in the analogous model. Correction coefficients are used in the analogy to take care of various assumptions. These are determined from existing test data. The same corrections are used to predict air temperatures for a modified configuration of the oven and a different vehicle. The method can be used to conduct control volume analysis of ovens to determine energy efficiency, and to study new vehicle or oven designs. -- Highlights: • Analogy of an automotive paint oven as a three stream cross flow heat exchanger. • The three streams are vehicle bodies, carriers and hot air. • Convection coefficients and inlet air stream temperatures from steady CFD simulations. • Analogy useful for overall energy efficiency analysis of conveyor ovens in general
Investigation of Condensing Ice Heat Exchangers for MTSA Technology Development
Padilla, Sebastian; Powers, Aaron; Ball, Tyler; Lacomini, Christie; Paul, Heather L.
Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal, carbon dioxide (CO2) and humidity control for a Portable Life Support Subsystem (PLSS). Metabolically-produced CO2 present in the ventilation gas of a PLSS is collected using a CO2-selective adsorbent via temperature swing adsorption. The temperature swing is initiated through cooling to well below metabolic temperatures. Cooling is achieved with a sublimation heat exchanger using water or liquid carbon dioxide (L CO2) expanded below sublimation temperature when exposed to low pressure or vacuum. Subsequent super heated vapor, as well as additional coolant, is used to further cool the astronaut. The temperature swing on the adsorbent is then completed by warming the adsorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. The water condensation from the ventilation gas represents a significant source of potential energy for the warming of the adsorbent bed as it represents as much as half of the energy potential in the moist ventilation gas. Designing a heat exchanger to efficiently transfer this energy to the adsorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210K to 280K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously.
Experimental analysis of an air–water heat pump with micro-channel heat exchanger
International Nuclear Information System (INIS)
A multi-port extruded (MPE) aluminium flat tube air heat exchanger was compared to a round tube finned coil (FC). The MPE heat exchanger has parallel flow vertical tube configuration with headers in horizontal position and conventional folded louvred fins. The two heat exchangers were mounted on a 10 kW cooling capacity R410A packaged air heat pump. They were sized to approximately obtain the same cooling and heating capacities in chiller and heating mode, respectively. Climatic room steady state tests without frosting phenomena occurring during heat pump operation, demonstrated that the round tube and the flat tube heat exchanger performance are comparable. The MPE heat exchanger was tested with different refrigerant inlet distributor/outlet tubes configurations to investigate the effect of liquid refrigerant distribution. Cycling frosting/defrosting operations were tested with two equivalent machines placed in parallel outdoor and working at full load condition, one of the units was equipped with the MPE heat exchanger while the other mounted a standard finned coil. Penalization factors were analytically introduced to evaluate frosting associated heating energy and energy efficiency degradation. Test results indicate that both the heat pumps are penalized by frost formation but both the penalization factors are higher for the MPE-unit than the FC-unit one in the −6 to 4 °C air dry bulb temperature range. For the two units, a roughly linear dependence of the heating energy penalization factor and of the energy efficiency factor from the difference between outdoor air and saturated air at the evaporation temperature humidity ratio can be pointed out. - Highlights: ► A multi-port aluminium flat tube heat exchanger was compared to a round tube finned one in a heat pump application. ► In steady state tests without frosting the round and the flat tube heat exchanger are comparable. ► Different inlet distributor/outlet tubes configurations were tested to
Comparisons of Heat Transfer Performance of a Closed-looped Oscillating Heat Pipe and Closed-looped Oscillating Heat Pipe with Check Valves Heat Exchangers
Directory of Open Access Journals (Sweden)
P. Meena
Full Text Available This research was to study the comparisons of heat transfer performance of closed-looped oscillating heat pipe and closed-looped oscillating heat pipe with check valves heat exchangers with R134a, Ethanol and water were used as the working fluids. A set of heat pipe heat exchanger (CLOHP and CLOHP/CV were made of copper tubes in combination of following dimension: 2.03 mm inside diameter: 40 turns, with 20, 10 and 20 cm for evaporator, adiabatic and condenser sections lengths. The working fluid was filled in the tube at the filling ratio of 50%. The evaporator section was given heat by heater while the condenser section was cooled by air. The adiabatic section was properly insulated. In the test operation, it could be concluded as follows. It indicated that the heat transfer performance of closed-looped oscillating heat pipe with check valves heat exchanger better than closed-looped oscillating heat exchanger.
Active heat exchange system development for latent heat thermal energy storage
Lefrois, R. T.; Knowles, G. R.; Mathur, A. K.; Budimir, J.
Active heat exchange concepts for use with thermal energy storage systems in the temperature range of 250 C to 350 C, using the heat of fusion of molten salts for storing thermal energy are described. Salt mixtures that freeze and melt in appropriate ranges are identified and are evaluated for physico-chemical, economic, corrosive and safety characteristics. Eight active heat exchange concepts for heat transfer during solidification are conceived and conceptually designed for use with selected storage media. The concepts are analyzed for their scalability, maintenance, safety, technological development and costs. A model for estimating and scaling storage system costs is developed and is used for economic evaluation of salt mixtures and heat exchange concepts for a large scale application. The importance of comparing salts and heat exchange concepts on a total system cost basis, rather than the component cost basis alone, is pointed out. The heat exchange concepts were sized and compared for 6.5 MPa/281 C steam conditions and a 1000 MW(t) heat rate for six hours. A cost sensitivity analysis for other design conditions is also carried out.
Compact/micro heat exchangers – Their role in heat pumping equipment
Kew, PA; Reay, DA; 2nd Micro and Nano Flows Conference (MNF2009)
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. Compact and micro-heat exchangers have many advantages over their larger ...
Fouling characteristics of compact heat exchangers and enhanced tubes.
Energy Technology Data Exchange (ETDEWEB)
Panchal, C. B.; Rabas, T. J.
Fouling is a complex phenomenon that (1) encompasses formation and transportation of precursors, and (2) attachment and possible removal of foulants. A basic understanding of fouling mechanisms should guide the development of effective mitigation techniques. The literature on fouling in complex flow passages of compact heat exchangers is limited; however, significant progress has been made with enhanced tubes.
40 CFR 63.654 - Heat exchange systems.
..., Sampling Procedures Manual, Appendix P: Cooling Tower Monitoring, prepared by Texas Commission on..., dated January 2003, Sampling Procedures Manual, Appendix P: Cooling Tower Monitoring, prepared by Texas... the convenience of the user, the revised text is set forth as follows: § 63.654 Heat exchange...
40 CFR 63.104 - Heat exchange system requirements.
... subpart shall monitor each heat exchange system used to cool process equipment in a chemical manufacturing process unit meeting the conditions of § 63.100 (b)(1) through (b)(3) of this subpart, except for chemical... prior to being returned to the process equipment and the exit is the point at which the cooling water...
Micro heat exchanger by using MEMS impinging jets
Wu, S.; Mai, J; Tai, Y. C.; Ho, C. M.
A micro impinging-jet heat exchanger is presented here. Heat transfer is studied for single jet, slot arrays and jet arrays. In order to facilitate micro heat transfer measurements with these devices, a MEMS sensor chip, which has an 8 x 8 temperature-sensor array on one side, and an integrated heater on the other side has been designed and fabricated. This sensor chip allows 2-D surface temperature measurement with various jets impinging on it. It is found that micro impinging jets can...
Ground Source Heat Pump Sub-Slab Heat Exchange Loop Performance in a Cold Climate
Energy Technology Data Exchange (ETDEWEB)
Mittereder, Nick [IBACOS, Inc., Pittsburgh, PA (United States); Poerschke, Andrew [IBACOS, Inc., Pittsburgh, PA (United States)
This report presents a cold-climate project that examines an alternative approach to ground source heat pump (GSHP) ground loop design. The innovative ground loop design is an attempt to reduce the installed cost of the ground loop heat exchange portion of the system by containing the entire ground loop within the excavated location beneath the basement slab. Prior to the installation and operation of the sub-slab heat exchanger, energy modeling using TRNSYS software and concurrent design efforts were performed to determine the size and orientation of the system. One key parameter in the design is the installation of the GSHP in a low-load home, which considerably reduces the needed capacity of the ground loop heat exchanger. This report analyzes data from two cooling seasons and one heating season.
Assessment of thermoelectric module with nanofluid heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Nnanna, A.G. Agwu [Micro- and Nano-scale Heat Transfer Laboratory, Department of Mechanical Engineering, Purdue University Calumet, 2200 169th Street, Hammond, IN 46323-2094 (United States)], E-mail: email@example.com; Rutherford, William; Elomar, Wessam; Sankowski, Brian [Micro- and Nano-scale Heat Transfer Laboratory, Department of Mechanical Engineering, Purdue University Calumet, 2200 169th Street, Hammond, IN 46323-2094 (United States)
For applications such as cooling of electronic devices, it is a common practice to sandwich the thermoelectric module between an integrated chip and a heat exchanger, with the cold-side of the module attached to the chip. This configuration results thermal contact resistances in series between the chip, module, and heat exchanger. In this paper, an appraisal of thermal augmentation of thermoelectric module using nanofluid-based heat exchanger is presented. The system under consideration uses commercially available thermoelectric module, 27 nm Al{sub 2}O{sub 3}-H{sub 2}O nanofluid, and a heat source to replicate the chip. The volume fraction of nanofluid is varied between 0% and 2%. At optimum input current conditions, experimental simulations were performed to measure the transient and steady-state thermal response of the module to imposed isoflux conditions. Data collected from the nanofluid-based exchanger is compared with that of deionized water. Results show that there exist a lag-time in thermal response between the module and the heat exchanger. This is attributed to thermal contact resistance between the two components. A comparison of nanofluid and deionized water data reveals that the temperature difference between the hot- and cold-side, {delta}T = T{sub h} - T{sub c} {approx} 0, is almost zero for nanofluid whereas {delta}T > 0 for water. When {delta}T {approx} 0, the contribution of Fourier effect to the overall heating is approximately zero hence enhancing the module cooling capacity. Experimental evidence further shows that temperature gradient across the thermal paste that bonds the chip and heat exchanger is much lower for the nanofluid than for deionized water. Low temperature gradient results in low resistance to the flow of heat across the thermal paste. The average thermal contact resistance, R = {delta}T/Q, is 0.18 and 0.12 deg. C/W, respectively for the deionized water and nanofluid. For the range of optimum current, 1.2 {<=} current {<=} 4
Novel Power Electronics Three-Dimensional Heat Exchanger: Preprint
Energy Technology Data Exchange (ETDEWEB)
Bennion, K.; Cousineau, J.; Lustbader, J.; Narumanchi, S.
Electric drive systems for vehicle propulsion enable technologies critical to meeting challenges for energy, environmental, and economic security. Enabling cost-effective electric drive systems requires reductions in inverter power semiconductor area. As critical components of the electric drive system are made smaller, heat removal becomes an increasing challenge. In this paper, we demonstrate an integrated approach to the design of thermal management systems for power semiconductors that matches the passive thermal resistance of the packaging with the active convective cooling performance of the heat exchanger. The heat exchanger concept builds on existing semiconductor thermal management improvements described in literature and patents, which include improved bonded interface materials, direct cooling of the semiconductor packages, and double-sided cooling. The key difference in the described concept is the achievement of high heat transfer performance with less aggressive cooling techniques by optimizing the passive and active heat transfer paths. An extruded aluminum design was selected because of its lower tooling cost, higher performance, and scalability in comparison to cast aluminum. Results demonstrated a heat flux improvement of a factor of two, and a package heat density improvement over 30%, which achieved the thermal performance targets.
The computational optimization of heat exchange efficiency in stack chimneys
Energy Technology Data Exchange (ETDEWEB)
Van Goch, T.A.J.
For many industrial processes, the chimney is the final step before hot fumes, with high thermal energy content, are discharged into the atmosphere. Tapping into this energy and utilizing it for heating or cooling applications, could improve sustainability, efficiency and/or reduce operational costs. Alternatively, an unused chimney, like the monumental chimney at the Eindhoven University of Technology, could serve as an 'energy channeler' once more; it can enhance free cooling by exploiting the stack effect. This study aims to identify design parameters that influence annual heat exchange in such stack chimney applications and optimize these parameters for specific scenarios to maximize the performance. Performance is defined by annual heat exchange, system efficiency and costs. The energy required for the water pump as compared to the energy exchanged, defines the system efficiency, which is expressed in an efficiency coefficient (EC). This study is an example of applying building performance simulation (BPS) tools for decision support in the early phase of the design process. In this study, BPS tools are used to provide design guidance, performance evaluation and optimization. A general method for optimization of simulation models will be studied, and applied in two case studies with different applications (heating/cooling), namely; (1) CERES case: 'Eindhoven University of Technology monumental stack chimney equipped with a heat exchanger, rejects heat to load the cold source of the aquifer system on the campus of the university and/or provides free cooling to the CERES building'; and (2) Industrial case: 'Heat exchanger in an industrial stack chimney, which recoups heat for use in e.g. absorption cooling'. The main research question, addressing the concerns of both cases, is expressed as follows: 'what is the optimal set of design parameters so heat exchange in stack chimneys is optimized annually for the cases in which a
VHTR engineering design study: intermediate heat exchanger program. Final report
Energy Technology Data Exchange (ETDEWEB)
The work reported is the result of a follow-on program to earlier Very High Temperature Reactor (VHTR) studies. The primary use of the VHTR is to provide heat for various industrial processes, such as hydrocarbon reforming and coal gasification. For many processes the use of an intermediate heat transfer barrier between the reactor coolant and the process is desirable; for some processes it is mandatory. Various intermediate heat exchanger (IHX) concepts for the VHTR were investigated with respect to safety, cost, and engineering design considerations. The reference processes chosen were steam-hydrocarbon reforming, with emphasis on the chemical heat pipe, and steam gasification of coal. The study investigates the critically important area of heat transfer between the reactor coolant, helium, and the various chemical processes.
VHTR engineering design study: intermediate heat exchanger program. Final report
International Nuclear Information System (INIS)
The work reported is the result of a follow-on program to earlier Very High Temperature Reactor (VHTR) studies. The primary use of the VHTR is to provide heat for various industrial processes, such as hydrocarbon reforming and coal gasification. For many processes the use of an intermediate heat transfer barrier between the reactor coolant and the process is desirable; for some processes it is mandatory. Various intermediate heat exchanger (IHX) concepts for the VHTR were investigated with respect to safety, cost, and engineering design considerations. The reference processes chosen were steam-hydrocarbon reforming, with emphasis on the chemical heat pipe, and steam gasification of coal. The study investigates the critically important area of heat transfer between the reactor coolant, helium, and the various chemical processes
Dual Expander Cycle Rocket Engine with an Intermediate, Closed-cycle Heat Exchanger
Greene, William D. (Inventor)
A dual expander cycle (DEC) rocket engine with an intermediate closed-cycle heat exchanger is provided. A conventional DEC rocket engine has a closed-cycle heat exchanger thermally coupled thereto. The heat exchanger utilizes heat extracted from the engine's fuel circuit to drive the engine's oxidizer turbomachinery.
Highly Integrated Heat Exchangers for Automotive Thermoelectric Generators (TEG) - Methodical functional integration and numerical analysis of TEG heat exchangers
Kober, Martin; Friedrich, Horst E.
•Functional integration by using the module structure of VDI Guidline 2221 •Comparison of three approaches to homogenise contact pressure •Multilayer fins is the only approach that achieve the requirements: •Homogeneous contact pressure •Low mechanical stress at TEM •Successful integration of thermal/mechanical functions within heat exchangers
Entropy generation extremum and entransy dissipation extremum for heat exchanger optimization
Institute of Scientific and Technical Information of China (English)
LIU XiongBin; MENG JiAn; GUO ZengYuan
The applicability of the extremum principles of entropy generation and entransy dissipation is studied for heat exchanger optimization. The extremum principle of entransy dissipation gives better optimization results when heat exchanger is only for the purpose of heating and cooling, while the extremum principle of entropy generation is better for the heat exchanger optimization when it works in the Brayton cycle. The two optimization principles are approximately equivalent when the temperature drops of the streams in a heat exchanger are small.
Studi Eksperimen Analisa Performa Compact Heat Exchanger Louvered Fin Flat Tube untuk pemanfaatan Waste Energy
Directory of Open Access Journals (Sweden)
Taqwim Ismail
Full Text Available Waste Heat Recovery merupakan instalasi yang digunakan untuk memanfaatkan kembali waste energy seperti exhaust gas. Penelitian dilakukan pada compact heat exchanger tipe louvered fin flat tube sebagai salah satu komponen penyusun waste heat recovery system. Eksperimen dilakukan dengan mendesain compact heat exchanger tipe louvered fin flat tube kemudian dilakukan pengujian pada compact heat exchanger yang telah didesain. Pengujian dilakukan dengan memberikan tiga variasi kecepatan putaran fan sisi exhaust gas, yaitu 0.2, 0.3, dan 0.4 m/s untuk mengetahui unjuk kerja yang berbeda dari compact heat exchanger yang telah didesain. Hasil yang didapatkan dari studi eksperimen ini adalah dimensi dari compact heat exchanger tipe louvered fin flat tube dan beberapa parameter yang menunjukkan unjuk kerja dari compact heat exchanger seperti nilai heat transfer baik dari sisi air maupun sisi exhaust gas, effectiveness, number of transfer unit (NTU, overall heat transfer coefficient, dan ΔTLMTD dari compact heat exchanger.
Heat exchanger modeling and identification for control of waste heat recovery systems in diesel engines
Feru, E.; Willems, F.P.T.; Rojer, C.; Jager, B. de; Steinbuch, M.
To meet future CO2 emission targets, Waste Heat Recovery systems have recently attracted much attention for automotive applications, especially for long haul trucks. This paper focuses on the development of a dynamic counter-flow heat exchanger model for control purposes. The model captures the dyna
Assessment of impact of borehole heat exchanger design on heat extraction/rejection efficiency
Directory of Open Access Journals (Sweden)
Gornov V.F.
Full Text Available The article considers the impact of design of borehole heat exchanger (BHE as one of the main elements of a geothermal heat pump system on its efficiency in the ground heat extraction/rejection. Four BHE modifications are considered: coaxial with metal and polyethylene outside tube as well as single and double U-shaped structures of polyethylene tubes. Numerical modeling resulted to data on the efficiency of these BHE modifications for rejection heat into ground (heat pump system in cooling mode, and ground heat extraction (heat pump system in heating mode. Numerical values were obtained and BHEs were ranked according to their efficiency in both operation modes. Besides, additional calculations were made for the most common modification - double U-shaped design - in the ground heat extraction mode for various tube sizes with various wall thicknesses.
Directory of Open Access Journals (Sweden)
P. Raveendiran
Full Text Available The heat transfer coefficients and friction factors of a baffled shell and heat pipe heat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heat pipe heat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of both hot and cold side of heat exchanger and mass flow rate of fluids were measured using an appropriate instrument. Different tests were performed from which condenser side heat transfer coefficient and friction factor were calculated. In all operating conditions it has been found that the heat transfer coefficient increases by increasing the mass flow rate and angle of inclination. The reduction in friction factor occurs when the Reynolds number is increased. The overall optimum experimental effectiveness of GABSHPHE has found to be 42% in all operating conditioning at ψ = 45o.
Numerical Modeling of Fin and Tube Heat Exchanger for Waste Heat Recovery
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study asso...... between fin and tube. The present numerical model predicts the performance of the heat exchanger design, therefore, can be applied to existing waste heat recovery systems to improve the overall performance with optimized design and process-dependent parameters....
Intensification of heat and mass transfer by ultrasound: application to heat exchangers and membrane separation processes.
Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E
This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions. PMID:25216897
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
de Jong, J A; Wijnant, Y H; de Boer, A
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.
Enhancement of heat exchange by on-chip engineered heat sink structure
Chong, Yonuk; Dresselhaus, Paul D.; Benz, Samuel P.
We report a method for improving heat exchange between cryo- cooled high power consuming devices and coolant. We fabricated a micro-machined monolithic heat sink structure on a high integration density superconducting Josephson device, and studied the effect of the heat sink on cooling of the device in detail. The monolithic heat sink structure showed a significant enhancement of cooling efficiency, which markedly improved the chip operation. The detailed mechanism of the enhancement still needs further modeling and study in order to optimize the design of the heat sink structure.
Boiling of Binary Zeotropic Blends in the Plate Heat Exchanger of the Heat Pump
Directory of Open Access Journals (Sweden)
Mezentseva Nadezhda N.
Full Text Available In this paper, we consider the process of boiling in the evaporator of the heat pump. Zeotropic binary refrigerants R32/R152a (30/70% and R32/R134a (30/70% are used as working medium. Calculations are made for brazed plate heat exchanger during boiling of zeotropic blend refrigerants with account of peculiarities of this process. Results of calculation of the heat transfer coefficient for zeotropic blends are given.
Numerical Simulation of Heat Transfer in a Gas Solid Crossflow Moving Packed Bed Heat Exchanger
Institute of Scientific and Technical Information of China (English)
Anyuan Liu; Shi Liu; Yufeng Duan; Zhonggang Pan
The mechanism of heat transfer in a crossfiow moving packed bed heat transfer exchanger is analyzed and a two dimensional heat transfer mathematical model has been developed based on the two fluid model (TFM) approach, in which both phases are considered to be continuous and fully interpenetrating. This model is solved by means of numerical method and the results are approximately in agreement with the experimental ones.
New ceramic heat exchangers with enhanced heat transfer properties for recuperative gas burners
Fino, Paolo
Heat recovery from waste gas is a major key process for increasing efficiency of thermal processes. The aim of the present work is to increase heat transfer coeffi cients of ceramic heat exchangers of recuperative burners using highly structured surface elements created from a textile precursor. The paper describes the chosen geometries and their thermal behavior, the ceramization process and the preliminary design of the new recuperative burners
Simulation of embedded heat exchangers of solar aided ground source heat pump system
Institute of Scientific and Technical Information of China (English)
王芳; 郑茂余; 邵俊鹏; 李忠建
Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year's running. It is beneficial for the system to operate for long period.
Fabrication of Wire Mesh Heat Exchangers for Waste Heat Recovery Using Wire-Arc Spraying
Rezaey, R.; Salavati, S.; Pershin, L.; Coyle, T.; Chandra, S.; Mostaghimi, J.
Waste heat can be recovered from hot combustion gases using water-cooled heat exchangers. Adding fins to the external surfaces of the water pipes inserted into the hot gases increases their surface area and enhances heat transfer, increasing the efficiency of heat recovery. A method of increasing the heat transfer surface area has been developed using a twin wire-arc thermal spray system to generate a dense, high-strength coating that bonds wire mesh to the outside surfaces of stainless steel pipes through which water passes. At the optimum spray distance of 150 mm, the oxide content, coating porosity, and the adhesion strength of the coating were measured to be 7%, 2%, and 24 MPa, respectively. Experiments were done in which heat exchangers were placed inside a high-temperature oven with temperature varying from 300 to 900 °C. Several different heat exchanger designs were tested to estimate the total heat transfer in each case. The efficiency of heat transfer was found to depend strongly on the quality of the bond between the wire meshes and pipes and the size of openings in the wire mesh.
Cleaning Schedule Optimization of Heat Exchanger Networks Using Particle Swarm Optimization
Biyanto, Totok R.; Suganda, Sumitra Wira; Matraji; Susatio, Yerry; Justiono, Heri; Sarwono
Oil refinery is one of industries that require huge energy consumption. The today technology advance requires energy saving. Heat integration is a method used to minimize the energy comsumption though the implementation of Heat Exchanger Network (HEN). CPT is one of types of Heat Exchanger Network (HEN) that functions to recover the heat in the flow of product or waste. HEN comprises a number of heat exchangers (HEs) that are serially connected. However, the presence of fouling in the heat ex...
Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer
Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.
Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in
Thermal energy storage systems using fluidized bed heat exchangers
Ramanathan, V.; Weast, T. E.; Ananth, K. P.
The viability of using fluidized bed heat exchangers (FBHX) for thermal energy storage (TES) in applications with potential for waste heat recovery was investigated. Of the candidate applications screened, cement plant rotary kilns and steel plant electric arc furnaces were identified, via the chosen selection criteria, as having the best potential for successful use of FBHX/TES system. A computer model of the FBHX/TES systems was developed and the technical feasibility of the two selected applications was verified. Economic and tradeoff evaluations in progress for final optimization of the systems and selection of the most promising system for further concept validation are described.
A Simple Tubesheet Layout Program for Heat Exchangers
Directory of Open Access Journals (Sweden)
S. Murali
Full Text Available The development of tubesheet layout program for shell and tube heat exchangers is presented in this study. Program is written in AutoLISP language, which provides standard tubesheet layout drawing as per standard codes and non standard tubsheet in AutoCAD Environment. The program computes the optimal number of tube count and lays out drawing with respecting constraints, including the shell ID, number of passes, center to center distance of tubes and tube outer diameter. Tubesheet layout drawing can be used as template for actual tubesheet. Furthermore the program is validated with open literature and shown good agreement with it. Besides the tubesheet for Heat exchangers this method can be extended to the tube counts of sheave plates and perforated plates of distillation column and Cooling Towers.
Numerical computation of sapphire crystal growth using heat exchanger method
Lu, Chung-Wei; Chen, Jyh-Chen
The finite element software FIDAP is employed to study the temperature and velocity distribution and the interface shape during a large sapphire crystal growth process using a heat exchanger method (HEM). In the present study, the energy input to the crucible by the radiation and convection inside the furnace and the energy output through the heat exchanger is modeled by the convection boundary conditions. The effects of the various growth parameters are studied. It is found that the contact angle is obtuse before the solid-melt interface touches the sidewall of the crucible. Therefore, hot spots always appear in this process. The maximum convexity decreases significantly when the cooling-zone radius (RC) increases. The maximum convexity also decreases significantly as the combined convection coefficient inside the furnace (hI) decreases.
High pressure ratio cryocooler with integral expander and heat exchanger
Crunkleton, J. A.; Smith, J. L., Jr.; Iwasa, Y.
A new 1 W, 4.2 K cryocooler is under development that is intended to miniaturize helium temperature refrigeration systems using a high-pressure-ratio Collins-type cycle. The configuration resulted from optimization studies of a saturated vapor compression (SCV) cycle that employs miniature parallel-plate heat exchangers. The basic configuration is a long displacer in a close-fitting, thin-walled cylinder. The displacer-to-cylinder gap is the high-pressure passage of the heat exchanger, and the low-pressure passage is formed by a thin tube over the OD of the cylinder. A solenoid-operated inlet valve admits 40 atm helium to the displacer-to-cylinder gap at room temperature, while the solenoid-operated exhaust valve operates at 4 atm. The single-stage cryocooler produces 1 W of refrigeration at 40 K without precooling and at 20 K with liquid nitrogen precooling.
The root caused analysis of leakaged heat exchanger tube
International Nuclear Information System (INIS)
AISI type 316L stainless steel was used as a heat exchanger tube material in an inter-cooler column. After less than a year of operation, severe corrosion failures occurred and a transverse opening leakage was observed on one of the heat exchanger tubes. The failed tube was carefully analyzed using various metallurgical laboratory equipments. The root cause of the tube leakage was believed due to the presence of horizontal micro and macro pores as a hydrogen gas entrapment during casting of the parent ingot. The overlapped and gaping pores formed notch on the shell side of the tube surface, and it increasingly evident when the use of a high-energy water-jet and metal brush as cleaning procedure results in an establishment of pitting type local-action corrosion cells penetrated the tube wall. As a result, corrosive fluid in the tube side dissolved into the cooling water, accelerating the corrosion process.
Condensing Heat Exchanger Concept Developed for Space Systems
Hasan, Mohammad M.; Nayagam, Vedha
The current system for moisture removal and humidity control for the space shuttles and the International Space Station uses a two-stage process. Water first condenses onto fins and is pulled through "slurper bars." These bars take in a two-phase mixture of air and water that is then separated by the rotary separator. A more efficient design would remove the water directly from the air without the need of an additional water separator downstream. For the Condensing Heat Exchanger for Space Systems (CHESS) project, researchers at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center are designing a condensing heat exchanger that utilizes capillary forces to collect and remove water and that can operate in varying gravitational conditions including microgravity, lunar gravity, and Martian gravity.
Major heat exchanger performance in Ontario Hydro-operated CANDU nuclear generating stations
International Nuclear Information System (INIS)
The performance of heat exchangers is described in terms of their impact on the unit in the form of forced outages and deratings as well as incapability due to scheduled outages. Some major problems with heat exchangers are highlighted. (auth)
The intensification study of heat exchange in pipes with the knurled screw
International Nuclear Information System (INIS)
The study results of heat exchange intensification in the tubes with double-thread knurled screw are presented. The Reynolds number range and knurl parameters at which optimum heat exchange intensification is provided are established
Optimisation of Double Pipe Helical Tube Heat Exchanger and its Comparison with Straight Double Tube Heat Exchanger
Kareem, Rashid
Optimization of double pipe helical coil heat exchanger with various optimizing parameters and its comparison with double pipe straight tube are the prime objectives of this paper. Numerical studies were performed with the aid of a commercial computational fluid dynamics package ANSYS FLUENT 14. In this paper the double pipe helical coil is analysed under turbulent flow conditions for optimum heat exchanger properties. The parameters used for optimization are cross-sectional shape and taper angles. Optimization analysis is being carried out for finding best cross sectional shape of heat exchanger coils by using rectangular, square, triangular and circular cross-sections. The tapered double pipe helical coil is then analysed for best heat transfer and pressure drop characteristics by varying the angle of taper. Finally, an optimum coil on the basis of all the analysis is selected. This optimized double pipe helical coil is compared with double pipe straight tube of equivalent cross-sectional area and length as that of unwounded length of double pipe helical coil.
María Fernanda Laborde; Laura Ivana Orifici; Ana María Pagano; María Cristina Gely
With the objective to aboard one of the challenges in Engineering teaching: It´s the application in professional practice?, along with attending to the actual requirements of achieve energetic efficiency in industrial process and to reuse wastes of food industry, this work, presents the application of heat exchange networks for the resolution of a real case: pre-treatment of waste cooking oils (WCO) withacid catalysis for biodiesel production. Different methods and software are applied to obt...
Eddy current detection of corrosion damage in heat exchanger tubes
International Nuclear Information System (INIS)
Eddy current is often the most effective nondestructive test method available for in-service inspection of small bore tubing in heat exchangers. The basic principles, advantages and shortcomings of the technique are outlined. Typical eddy current indications from corrosion-related defects such as stress corrosion cracks, pitting and tube denting under support plates are presented. Eddy current signals from features such as magnetite deposits and ferromagnetic inclusions which might be mistaken for defects are also discussed. (auth)
Negative Joule Heating in Ion-Exchange Membranes
Biesheuvel, P. M.; D. Brogioli; Hamelers, H. V. M.
In ion-exchange membrane processes, ions and water flow under the influence of gradients in hydrostatic pressure, ion chemical potential, and electrical potential (voltage), leading to solvent flow, ionic fluxes and ionic current. At the outer surfaces of the membranes, electrical double layers (EDLs) are formed (Donnan layers). When a current flows through the membrane, we argue that besides the positive Joule heating in the bulk of the membrane and in the electrolyte outside the membrane, t...
Heat exchangers and thermal energy storage concepts for the off-gas heat of steelmaking devices
International Nuclear Information System (INIS)
The fluctuating thermal emissions of electric arc furnaces require energy storage systems to provide downstream consumers with a continuous amount of thermal energy or electricity. Heat recovery systems based on thermal energy storage are presented. A comparison of different thermal energy storage systems has been performed. For the purpose, suitable heat exchangers for the off-gas heat have been developed. Dynamic process simulations of the heat recovery plants were necessary to check the feasibility of the systems and consider the non-steady-state off-gas emissions of the steelmaking devices. The implementation of a pilot plant into an existing off-gas duct of an electric arc furnace was required to check the real behavior of the heat exchanger and determine suitable materials in view of corrosion issues. The pilot plant is presented in this paper.
Non-newtonian heat transfer on a plate heat exchanger with generalized configurations
Energy Technology Data Exchange (ETDEWEB)
Carezzato, A.; Tadini, C.C.; Gut, J.A.W. [Department of Chemical Engineering, Escola Politecnica, University of Sao Paulo, Sao Paulo (Brazil); Alcantara, M.R. [Department of Fundamental Chemistry, Institute of Chemistry, University of Sao Paulo, Sao Paulo (Brazil); Telis-Romero, J. [Department of Food Engineering and Technology, Universidade Estadual Paulista, Sao Jose do Rio Preto (Brazil)
For the configuration optimization of plate heat exchangers (PHEs), the mathematical models for heat transfer and pressure drop must be valid for a wide range of operational conditions of all configurations of the exchanger or the design results may be compromised. In this investigation, the thermal model of a PHE is adjusted to fit experimental data obtained from non-Newtonian heat transfer for eight different configurations, using carboxymethylcellulose solutions (CMC) as test fluid. Although it is possible to successfully adjust the model parameters, Newtonian and non-Newtonian heat transfer cannot be represented by a single generalized correlation. In addition, the specific heat, thermal conductivity and power-law rheological parameters of CMC solutions were correlated with temperature, over a range compatible with a continuous pasteurization process. (Abstract Copyright [2007], Wiley Periodicals, Inc.)
Analysis of operating modes of a ground source heat pump with short helical heat exchangers
International Nuclear Information System (INIS)
Highlights: • The work focuses on the short helical-shaped pipe ground heat exchanger. • Multi-year integrated simulations of ground source heat pumps are carried out. • The simulation tool is validated with field measurements in cooling operation. • The effect of operating modes on the energy efficiency of the heat pump is shown. • The influence of grouting material and diameter of heat exchanger is analysed. - Abstract: This study focuses on different operating modes of a ground source heat pump system in residential buildings. Ground coupling was made using a closed loop system consisting of a helical shaped pipe installed at a shallow depth. Few studies have examined this particular ground heat exchanger. The analysis was carried out using a detailed numerical model capable of considering the geometry of the helical ground heat exchanger as well as the effects of axial thermal conduction and the weather at ground level, variables which cannot be ignored when shallow depths are being investigated. Field measurements were used to validate the model before it was utilized. In addition, the simulation tool considered the entire ground source heat pump system, including both the borehole field and the heat pump. The energy efficiency of the heat pump in three operating modes (continuous daytime, continuous nighttime, and intermittent mode) over a ten year period was analysed. The simulations were performed in two different climatic zones maintaining the daily energy load of the building unmodified. Finally, the effect of the grouting material of the helical ground heat exchanger and of the diameters of both the borehole and the helix on the system's energy performance was also investigated. Results indicated that the seasonal energy efficiency of the heat pump was approximately the same for the three operating modes and that energy efficiency was nearly constant during the day when the system was operating on an hourly intermittent basis. When the
The Role of Filtration in Maintaining Clean Heat Exchanger Coils
Energy Technology Data Exchange (ETDEWEB)
Li Yang; James E. Braun; Eckhard A. Groll
The main purpose of the study was to investigate the role of filtration in maintaining clean heat exchanger coils and overall performance. Combinations of 6 different levels of filtration (MERV 14, 11, 8, 6, 4, and no filter) and 4 different coils (an eight-row lanced-fin coil, HX8L), (an eight-row wavy-fin coil, HX8W), (a four-row lanced-fin coil, HX4L) and (a two-row lanced-fin coil, HX2L) were tested at 4 different air velocities (1.52, 2.03, 2.54,3.05 m/s (300, 400, 500, 600 ft/min)). The fouled conditions were obtained after injection of 600 grams of ASHRAE standard dust upstream of the filter/coil combination. This magnitude of dust is representative of a year of normal operation for an air conditioning system. The air-side pressure drops of the coils and filters and air-side heat transfer coefficients of the coils were determined from the measurements under the clean and fouled conditions. Depending upon the filter and coil test, the coil pressure drops increased in the range of 6%-30% for an air velocity at 2.54 m/s (500 ft/min). The impact was significantly greater for tests performed without a filter. The largest relative effect of fouling on pressure drop occurs for coils with fewer rows and having lanced fins. Coils with a greater number of rows can hold more dust so that a fixed amount of dust has a relatively smaller impact. The impact of fouling on air-side heat transfer coefficients was found to be relatively small. In some cases, heat transfer was actually enhanced due to additional turbulence caused by the presence of dust. The experimental results for pressure drops and heat transfer coefficients were correlated and the correlations were implemented within computer models of prototypical rooftop air conditioners and used to evaluate the impact of fouling on cooling capacity and EER. The equipment cooling capacity is reduced with fouling primarily because of a decrease in air flow due to the increase pressure drop rather than due to changes in h
Horizontal Heat Exchanger Design and Analysis for Passive Heat Removal Systems
Energy Technology Data Exchange (ETDEWEB)
Vierow, Karen
This report describes a three-year project to investigate the major factors of horizontal heat exchanger performance in passive containment heat removal from a light water reactor following a design basis accident LOCA (Loss of Coolant Accident). The heat exchanger studied in this work may be used in advanced and innovative reactors, in which passive heat removal systems are adopted to improve safety and reliability The application of horizontal tube-bundle condensers to passive containment heat removal is new. In order to show the feasibility of horizontal heat exchangers for passive containment cooling, the following aspects were investigated: 1. the condensation heat transfer characteristics when the incoming fluid contains noncondensable gases 2. the effectiveness of condensate draining in the horizontal orientation 3. the conditions that may lead to unstable condenser operation or highly degraded performance 4. multi-tube behavior with the associated secondary-side effects This project consisted of two experimental investigations and analytical model development for incorporation into industry safety codes such as TRAC and RELAP. A physical understanding of the flow and heat transfer phenomena was obtained and reflected in the analysis models. Two gradute students (one funded by the program) and seven undergraduate students obtained research experience as a part of this program.
Thermal design of spiral heat exchangers and heat pipes through global best algorithm
Turgut, Oğuz Emrah; Çoban, Mustafa Turhan
This study deals with global best algorithm based thermal design of spiral heat exchangers and heat pipes. Spiral heat exchangers are devices which are highly efficient in extremely dirty and fouling process duties. Spirals inherent in design maintain high heat transfer coefficients while avoiding hazardous effects of fouling and uneven fluid distribution in the channels. Heat pipes have wide usage in industry. Thanks to the two phase cycle which takes part in operation, they can transfer high amount of heat with a negligible temperature gradient. In this work, a new stochastic based optimization method global best algorithm is applied for multi objective optimization of spiral heat exchangers as well as single objective optimization for heat pipes. Global best algorithm is easy-to-implement, free of derivatives and it can be reliably applied to any optimization problem. Case studies taken from the literature approaches are solved by the proposed algorithm and results obtained from the literature approaches are compared with thosed acquired by GBA. Comparisons reveal that GBA attains better results than literature studies in terms of solution accuracy and efficiency.
Thermal-hydraulic issues of flow boiling and condensation in organic Rankine cycle heat exchangers
Mikielewicz, Jarosław; Mikielewicz, Dariusz
In the paper presented are the issues related to the design and operation of micro heat exchangers, where phase changes can occur, applicable to the domestic micro combined heat and power (CHP) unit. Analysed is the stability of the two-phase flow in such unit. A simple hydraulic model presented in the paper enables for the stability analysis of the system and analysis of disturbance propagation caused by a jump change of the flow rate. Equations of the system dynamics as well as properties of the working fluid are strongly non-linear. A proposed model can be applicable in designing the system of flow control in micro heat exchangers operating in the considered CHP unit.
Fouling of HVAC fin and tube heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Siegel, Jeffrey; Carey, Van P.
Fin and tube heat exchangers are used widely in residential, commercial and industrial HVAC applications. Invariably, indoor and outdoor air contaminants foul these heat exchangers. This fouling can cause decreased capacity and efficiency of the HVAC equipment as well as indoor air quality problems related to microbiological growth. This paper describes laboratory studies to investigate the mechanisms that cause fouling. The laboratory experiments involve subjecting a 4.7 fins/cm (12 fins/inch) fin and tube heat exchanger to an air stream that contains monodisperse particles. Air velocities ranging from 1.5-5.2 m/s (295 ft/min-1024 ft/min) and particle sizes from 1--8.6 {micro}m are used. The measured fraction of particles that deposit as well as information about the location of the deposited material indicate that particles greater than about 1 {micro}m contribute to fouling. These experimental results are used to validate a scaling analysis that describes the relative importance of several deposition mechanisms including impaction, Brownian diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The analysis is extended to apply to different fin spacings and particle sizes typical of those found in indoor air.
Bypass Selection for Control of Heat Exchanger Network
Institute of Scientific and Technical Information of China (English)
SUN Lin; LUO Xionglin; HOU Benquan; BAI Yujie
Considering the flexibility and controllability of heat exchanger networks (HENs),bypasses are widely used for effective control of process stream target temperatures.However,the optimal location for the bypass is generally difficult to design with the trade-off between controllability and capital investments.In this paper,based on the steady-state model of heat exchanger networks the optimal bypass location was firstly selected by iteratively calculating the non-square Relative Gain Array (ns-RGA).To simplify the calculation process,rules of bypass selection were also proposed.In order to evaluate this method,then,the structural controllability of heat exchanger networks was analyzed.With both the consideration of the controllability and capital investments,the bypasses locations were finally selected.A case study on the HEN in Crude Distillation Unit was presented in which the ns-RGA and structural controllability were used to select bypasses and also to evaluate the results.
A cryogenic heat exchanger with bypass and throttling and its thermodynamic analysis
Tao, X.; Liu, D. L.; Wang, L. Y.; Shen, J.; Gan, Z. H.
A precooled Joule-Thomson (J-T) cooler refrigerates at liquid helium temperature. Its third stage heat exchanger works below 20 K. Hot fluid cannot be sufficiently cooled due to nonidealism of the heat exchanger and helium-4 properties. In a J-T cycle of low pressure ratio, the heat exchanger with bypass and throttling improves the refrigeration capacity. Bypass and throttling reduces the temperature difference and entropy generation within the heat exchanger.
Quantification of Liquid Refrigerant Distribution in Parallel Flow Microchannel Heat Exchanger Using Infrared Thermography
Li, Huize; Hrnjak, Predrag S.
This paper presents a method to quantify the distribution of liquid refrigerant mass flow rate in parallel flow microchannel heat exchanger from the infrared images. This method can be used for several types of heat exchangers: evaporators, condensers, gas-coolers and etc., also it can be applied to various heat exchanger designs: different inlet/outlet locations, different flow configurations and etc. After being implemented in a heat exchanger model, this method is validated against experim...
Performance Comparison Of Round Tubes Finned Heat Exchangers And Macro Micro-Channel Heat Exchangers In A Low Capacity Heat Pump
Zoughaib, A; Mortada, S; Khayat, F; Arzano-Daurelle, C; Teuillieres, C
Micro-channel heat exchangers (MCHE) are used in automobile applications due to their low weight and high compactness. Those MCHE are just gaining interest in stationary application and they have a great potential for low heating capacity heat pumps to be installed in "passive houses" where the heating demand is 3 to 5 times lower than in the current new individual houses built in European countries. In this paper, a low capacity integrated air to air heat pump prototype is used to perform an...
Determining the Heat Exchange Capacity of Underground Coal Mines in Ohio
Richardson, J. J.; Lopez, D. A.; Leftwich, T. E.; Wolfe, M. E.; Angle, M. P.; Fugitt, F. L.
Conventionally, Ground Source Heat Pumps (GSHP) exploit either saturated bedrock/soils or large surface water bodies as the heat source/sink for the heating and cooling systems. In areas with flooded mines or large subsurface water bodies, it is possible to utilize the water within the voids as the heat source/sink in GSHPs. Utilizing the water within subsurface voids a heat exchanger instead of the traditional saturated bedrock/soils has the potential to be more efficient in heating and cooling applications. The water within the void space is a better thermal conductor than bedrock and soils. Additionally, it is possible that, in a saturated void the heat can be carried away from the exchange site at a greater rate, improving the potential for thermal exchange. This study is focused on characterizing the potential overall heat exchange capacity for flooded mine sites within Ohio. To achieve the overall potential exchange capacity, possible maximum and minimum mine water residence times, effective mine volumes, groundwater recharge rates, maximum and minimum possible linear groundwater velocity, groundwater flow direction, and average ambient mine temperatures were calculated using GIS software and groundwater recharge data from the United States Geological Survey, and characteristics of physical parameters for the mines from the Ohio Geological Survey. The potential linear mine water velocities were calculated by creating a theoretical cross sectional area in the direction of estimated groundwater flow with a respective length of the mine in the direction of groundwater flow and width of the coal bed thickness. It was assumed that all of water entering the mine void exited the through the cross sectional area. By dividing the volume of water entering the mine per year by the cross sectional area, the linear groundwater velocities were estimated. By using the specific heat of water at the estimated temperatures and the volumes of water within the mines, possible
Optimal Allocation of Heat Exchanger Inventory Associated with Fixed Power Output or Fixed Heat Transfer Rate Input
Directory of Open Access Journals (Sweden)
M. Costea
Full Text Available The purpose of this study is to determine the optimal distribution of the heat transfer surface area or conductance among the Stirling engine heat exchangers when the minimum of the total heat transfer surface area of the heat exchangers is sought. The optimization procedure must fulfill one of the following constraints: (1 fixed power output of the engine, (2 fixed heat transfer rate available at the source, or (3 fixed power output and heat transfer rate at the source. Internal and external irreversibilities of the Stirling engine are considered. An analytic approach, when heat transfer occurs at small temperature differences at the heat reservoirs, provides several restrictions with regard to variables of the model. A sensitivity analysis of the minimum of the total heat transfer surface area of the heat exchangers with respect to these variables and parameters is presented. The results show optimal temperatures of the working fluid and optimum allocation of heat exchanger inventory.
Secondary Heat Exchanger Design and Comparison for Advanced High Temperature Reactor
Energy Technology Data Exchange (ETDEWEB)
Piyush Sabharwall; Ali Siahpush; Michael McKellar; Michael Patterson; Eung Soo Kim
The goals of next generation nuclear reactors, such as the high temperature gas-cooled reactor and advance high temperature reactor (AHTR), are to increase energy efficiency in the production of electricity and provide high temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process heat transport system. The need for efficiency, compactness, and safety challenge the boundaries of existing heat exchanger technology, giving rise to the following study. Various studies have been performed in attempts to update the secondary heat exchanger that is downstream of the primary heat exchanger, mostly because its performance is strongly tied to the ability to employ more efficient conversion cycles, such as the Rankine super critical and subcritical cycles. This study considers two different types of heat exchangers—helical coiled heat exchanger and printed circuit heat exchanger—as possible options for the AHTR secondary heat exchangers with the following three different options: (1) A single heat exchanger transfers all the heat (3,400 MW(t)) from the intermediate heat transfer loop to the power conversion system or process plants; (2) Two heat exchangers share heat to transfer total heat of 3,400 MW(t) from the intermediate heat transfer loop to the power conversion system or process plants, each exchanger transfers 1,700 MW(t) with a parallel configuration; and (3) Three heat exchangers share heat to transfer total heat of 3,400 MW(t) from the intermediate heat transfer loop to the power conversion system or process plants. Each heat exchanger transfers 1,130 MW(t) with a parallel configuration. A preliminary cost comparison will be provided for all different cases along with challenges and recommendations.
Analytical and Numerical Study on the Uniformity of Temperature Difference Field in Heat Exchangers
Institute of Scientific and Technical Information of China (English)
Zhi-XinLi; Da-XiXiong; 等
The relations of the uniformity factor of temperature difference field with the effctiveness of heat exchangers were studied analytically and numerically.The results for eleven kinds of heat exchangers show that the more uniform the temperature difference field,the higher the effctiveness of heat exchanger for a given Ntu and Cr.
Modeling heat efficiency, flow and scale-up in the corotating disc scraped surface heat exchanger
DEFF Research Database (Denmark)
Friis, Alan; Szabo, Peter; Karlson, Torben
A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer...... performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key...
扭曲椭圆管换热的壳程强化传热特性%Shell side heat transfer enhancement in twisted elliptical tube heat exchanger
Institute of Scientific and Technical Information of China (English)
谭祥辉; 孙赫; 张立振; 朱冬生
通过搭建扭曲椭圆管换热器壳程传热与压降性能测试平台,对扭曲椭圆管换热器壳程传热与压降性能进行了实验测试,以实验数据为基础对前人得到的壳程传热与压降性能计算准则关系式的应用范围进行了分析,同时拟合得到了测试用扭曲椭圆管换热器壳程传热与压降性能计算准则关系式,设计了与测试扭曲椭圆管换热器结构类似的折流板换热器以及折流杆换热器,采用相关计算方法对换热器的传热与压降性能进行了计算和比较,并分析了3台换热器的综合性能,结果显示扭曲椭圆管换热器传热效果好、压降低,具有很好的工业应用前景.%Heat transfer and pressure drop of twisted elliptical tube heat exchanger with FrM = 79 are tested in the present work. Based on the experimental result, the application range of previous correlations for twisted elliptical tube heat exchanger with FrM>232 and FrM = 64 is analyzed, and correlations of the tested heat exchanger with FrM = 79 are derived. The testing result indicates that there exists a change of fluid flowing state when Re, increases to 8000. Two heat exchangers with similar geometric parameters to the tested one but supported by segmental baffles and rod baffles are designed. Their shell side heat transfer coefficients and pressure drops are calculated with Bell-Delaware method and Gentry's method, respectively. Heat transfer coefficients and pressure drops of the two designed heat exchangers are compared with the tested twisted elliptical tube heat exchanger. Comprehensive performance of the three heat exchangers is studied. The twisted elliptical tube heat exchanger gives the highest heat transfer coefficient and lowest pressure drop. This type of heat exchanger has the advantages of segmental heat exchanger and rod baffle heat exchanger and will be widely used in the industry.
Comparison of heat transfer performances of helix baffled heat exchangers with different baffle configurations
Institute of Scientific and Technical Information of China (English)
Cong Dong; Yaping Chen; Jiafeng Wu
Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical baffles of different baffle shapes and assembly configurations, i.e., two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers, the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as wel as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20° (20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure dropΔpo, the highest overal heat transfer coefficient K, shel-side heat transfer coefficient ho and shel-side average comprehensive index ho/Δpo.
Negative Joule Heating in Ion-Exchange Membranes
Biesheuvel, P M; Hamelers, H V M
In ion-exchange membrane processes, ions and water flow under the influence of gradients in hydrostatic pressure, ion chemical potential, and electrical potential (voltage), leading to solvent flow, ionic fluxes and ionic current. At the outer surfaces of the membranes, electrical double layers (EDLs) are formed (Donnan layers). When a current flows through the membrane, we argue that besides the positive Joule heating in the bulk of the membrane and in the electrolyte outside the membrane, there is also negative Joule heating in one of the EDLs. We define Joule heating as the inner product of the two vectors current and field strength. Also when fluid flows through a charged membrane, at one side of the membrane there is pressure-related cooling, due to the osmotic and hydrostatic pressure differences across the EDLs.
A probabilistic model of a porous heat exchanger
Agrawal, O. P.; Lin, X. A.
This paper presents a probabilistic one-dimensional finite element model for heat transfer processes in porous heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional model of heat transfer phenomenon in superfluid flow through a porous media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.
Optimizing the Heat Exchanger Network of a Steam Reforming System
DEFF Research Database (Denmark)
Nielsen, Mads Pagh; Korsgaard, Anders Risum; Kær, Søren Knudsen
Proton Exchange Membrane (PEM) based combined heat and power production systems are highly integrated energy systems. They may include a hydrogen production system and fuel cell stacks along with post combustion units optionally coupled with gas turbines. The considered system is based on a natural...... gas steam reformer along with gas purification reactors to generate clean hydrogen suited for a PEM stack. The temperatures in the various reactors in the fuel processing system vary from around 1000°C to the stack temperature at 80°C. Furthermore, external heating must be supplied to the endothermic...... steam reforming reaction and steam must be generated. The dependence of the temperature profiles on conversion in shift reactors for gas purification is also significant. The optimum heat integration in the system is thus imperative in order to minimize the need for hot and cold utilities. A rigorous 1D...
Investigation of the thermal efficiency of a staggered elliptic-tube heat exchanger for aeroengine applications
Kritikos, K; Albanakis, C.; Missirlis, D.; Vlahostergios, Z.; Goulas, A.; Storm, P.
Abstract In this paper, a numerical investigation of the thermal performance of a heat exchanger designed for aero engine applications is performed with the use of computational fluid dynamics (CFD). For this purpose, the exact geometry of the heat exchanger was modeled, and additionally the use of a porous medium methodology was adopted. For the latter the behaviour of the heat exchanger was described by experimentally derived pressure drop and heat transfer laws. The heat transfe...
Studi Eksperimen Analisa Performa Compact Heat Exchanger Louvered Fin Flat Tube untuk pemanfaatan Waste Energy
Taqwim Ismail; Ary Bachtiar Khrisna Putra
Waste Heat Recovery merupakan instalasi yang digunakan untuk memanfaatkan kembali waste energy seperti exhaust gas. Penelitian dilakukan pada compact heat exchanger tipe louvered fin flat tube sebagai salah satu komponen penyusun waste heat recovery system. Eksperimen dilakukan dengan mendesain compact heat exchanger tipe louvered fin flat tube kemudian dilakukan pengujian pada compact heat exchanger yang telah didesain. Pengujian dilakukan dengan memberikan tiga variasi kecepatan putaran fan...
Feasibility study of helically coiled tube condensation heat exchanger for a passive auxiliary feedwater system
International Nuclear Information System (INIS)
The Passive Auxiliary Feedwater System (PAFS) with nearly-horizontal heat exchangers is one of passive safety features of APR+ (Advanced Power Reactor Plus) which provides the auxiliary feedwater by means of natural circulation with condensation. It is feasible to increase the heat transfer capacity of the PAFS by employing a helically coiled heat exchanger due to additional secondary flow effect by centrifugal force. In addition, a compact and flexible design can be achieved in a fixed volume by using the helically coiled heat exchanger, which is one of the most important merits of implementing this heat exchanger. In this paper, the helically coiled heat exchanger has been employed for the PAFS instead of nearly-horizontal heat exchanger. In order to evaluate the heat transfer performance of the helically coiled heat exchanger, an in-tube condensation heat transfer correlation by Wongwises has been introduced into the system analysis code, MARS-KS. A comparative numerical study was conducted for both heat exchangers. The result shows that helically coiled heat exchanger has 20% higher heat transfer efficiency than existing nearly-horizontal heat exchanger. (author)
Entransy dissipation number and its application to heat exchanger performance evaluation
Institute of Scientific and Technical Information of China (English)
GUO JiangFeng; CHENG Lin; XU MingTian
Based on the concept of the entransy which characterizes heat transfer ability,a new heat exchanger performance evaluation criterion termed the entransy dissipation number is established.Our analysis shows that the decrease of the entransy dissipation number always increases the heat exchanger effectiveness for fixed heat capacity rate ratio.Therefore,the smaller the entransy dissipation number,the better the heat exchanger performance is.The entransy dissipation number in terms of the number of exchanger heat transfer units or heat capacity rate ratio correctly exhibits the global performance of the counter-,cross-and parallel-flow heat exchangers.In comparison with the heat exchanger performance evaluation criteria based on entropy generation,the entransy dissipation number demonstrates some distinct advantages.Furthermore,the entransy dissipation number reflects the degree of irreversibility caused by flow imbalance.
Specialists' meeting on heat exchanging components of gas-cooled reactors
International Nuclear Information System (INIS)
The objective of the Meeting sponsored by IAEA was to provide a forum for the exchange and discussion of technical information related to heat exchanging and heat conducting components for gas-cooled reactors. The technical part of the meeting covered eight subjects: Heat exchanging components for process heat applications, design and requirements, and research and development programs; Status of the design and construction of intermediate He/He exchangers; Design, construction and performance of steam generators; Metallic materials and design codes; Design and construction of valves and hot gas ducts; Description of component test facilities and test results; Manufacturing of heat exchanging components
Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Taboas, Francisco [Universidad de Cordoba, Campus de Rabanales, Edificio Leonardo da Vinci, 14014 Cordoba (Spain); Valles, Manel; Bourouis, Mahmoud; Coronas, Alberto [CREVER - Universitat Rovira i Virgili, Av. Paisos Catalans No. 26, 43007 Tarragona (Spain)
The objective of this work is to contribute to the development of plate heat exchangers as desorbers for ammonia/water absorption refrigeration machines driven by waste heat or solar energy. In this study, saturated flow boiling heat transfer and the associated frictional pressure drop of ammonia/water mixture flowing in a vertical plate heat exchanger is experimentally investigated. Experimental data is presented to show the effects of heat flux between 20 and 50 kW m{sup -2}, mass flux between 70 and 140 kg m{sup -2} s{sup -1}, mean vapour quality from 0.0 to 0.22 and pressure between 7 and 15 bar, for ammonia concentration between 0.42 and 0.62. The results show that for the selected operating conditions, the boiling heat transfer coefficient is highly dependent on the mass flux, whereas the influence of heat flux and pressure are negligible mainly at higher vapour qualities. The pressure drop increases with increasing mass flux and quality. However, the pressure drop is independent of the imposed heat flux. (author)
Thermal-economic optimization of an air-cooled heat exchanger unit
International Nuclear Information System (INIS)
Thermodynamic modeling and optimal design of an air-cooled heat exchanger (ACHE) unit are developed in this study. For this purpose, ε–NTU method and mathematical relations are applied to estimate the fluids outlet temperatures and pressure drops in tube and air sides. The main goal of this study is minimizing of two conflicting objective functions namely the temperature approach and the minimum total annual cost, simultaneously. For this purpose, fast and elitist non-dominated sorting genetic-algorithm (NSGA-II) is applied to minimize the objective functions by considering ten design parameters. In addition, a set of typical constraints, governing on the ACHE unit design, is subjected to obtain more practical optimum design points. Furthermore, sensitivity analysis of change in the objective functions, when the optimum design parameters vary, is conducted and the degree of each parameter on conflicting objective functions has been investigated. Finally, a selection procedure of the best optimum point is introduced and final optimum design point is determined. -- Highlights: ► Multi-objective optimization of air-cooled heat exchanger. ► Considering ten new design parameters in this type of heat exchanger. ► A detailed cost function is used to estimate the heat exchanger investment cost. ► Presenting a mathematical relation for optimum total cost vs. temperature approach. ► The sensitivity analysis of parameters in the optimum situation
Effectiveness of evolutionary algorithms for optimization of heat exchangers
International Nuclear Information System (INIS)
Highlights: • Design optimization of shell and tube heat exchangers. • Comparing performance of three evolutionary optimization algorithms. • Conducting comprehensive simulations for design optimization. • Cuckoo search demonstrates the best performance. - Abstract: This paper comprehensively investigates performance of evolutionary algorithms for design optimization of shell and tube heat exchangers (STHX). Genetic algorithm (GA), firefly algorithm (FA), and cuckoo search (CS) method are implemented for finding the optimal values for seven key design variables of the STHX model. ∊-NTU method and Bell-Delaware procedure are used for thermal modeling of STHX and calculation of shell side heat transfer coefficient and pressure drop. The purpose of STHX optimization is to maximize its thermal efficiency. Obtained results for several simulation optimizations indicate that GA is unable to find permissible and optimal solutions in the majority of cases. In contrast, design variables found by FA and CS always lead to maximum STHX efficiency. Also computational requirements of CS method are significantly less than FA method. As per optimization results, maximum efficiency (83.8%) can be achieved using several design configurations. However, these designs are bearing different dollar costs. Also it is found that the behavior of the majority of decision variables remains consistent in different runs of the FA and CS optimization processes
Development of Passive Fuel Cell Thermal Management Heat Exchanger
Burke, Kenneth A.; Jakupca, Ian J.; Colozza, Anthony J.
The NASA Glenn Research Center is developing advanced passive thermal management technology to reduce the mass and improve the reliability of space fuel cell systems for the NASA Exploration program. The passive thermal management system relies on heat conduction within highly thermally conductive cooling plates to move the heat from the central portion of the cell stack out to the edges of the fuel cell stack. Using the passive approach eliminates the need for a coolant pump and other cooling loop components within the fuel cell system which reduces mass and improves overall system reliability. Previous development demonstrated the performance of suitable highly thermally conductive cooling plates that could conduct the heat, provide a sufficiently uniform temperature heat sink for each cell of the fuel cell stack, and be substantially lighter than the conventional thermal management approach. Tests were run with different materials to evaluate the design approach to a heat exchanger that could interface with the edges of the passive cooling plates. Measurements were made during fuel cell operation to determine the temperature of individual cooling plates and also to determine the temperature uniformity from one cooling plate to another.
Performance of Helical Coil Heat Recovery Exchanger using Nanofluid as Coolant
Directory of Open Access Journals (Sweden)
Navid Bozorgan
Full Text Available Nanofluids are expected to be a promising coolant condidate in chemical processes for heat transfer system size reduction. This paper focuses on reducing the number of turns in a helical coil heat recovery exchanger with a given heat exchange capacity in a biomass heating plant using γ-Al2O3/n-decane nanofluid as coolant. The nanofluid flows through the tubes and the hot n-hexane flows through the shell. The numerical results show that using nanofluid as coolant in a helical coil heat exchanger can reduce the manufacturing cost of the heat exchanger and pumping power by reducing the number of turns of the coil.
Fabrication of High-Temperature Heat Exchangers by Plasma Spraying Exterior Skins on Nickel Foams
Hafeez, P.; Yugeswaran, S.; Chandra, S.; Mostaghimi, J.; Coyle, T. W.
Thermal-sprayed heat exchangers were tested at high temperatures (750 °C), and their performances were compared to the foam heat exchangers made by brazing Inconel sheets to their surface. Nickel foil was brazed to the exterior surface of 10-mm-thick layers of 10 and 40 PPI nickel foam. A plasma torch was used to spray an Inconel coating on the surface of the foil. A burner test rig was built to produce hot combustion gases that flowed over exposed face of the heat exchanger. Cooling air flowed through the foam heat exchanger at rates of up to 200 SLPM. Surface temperature and air inlet/exit temperature were measured. Heat transfer to air flowing through the foam was significantly higher for the thermally sprayed heat exchangers than for the brazed heat exchangers. On an average, thermally sprayed heat exchangers show 36% higher heat transfer than conventionally brazed foam heat exchangers. At low flow rates, the convective resistance is large (~4 × 10-2 m2 K/W), and the effect of thermal contact resistance is negligible. At higher flow rates, the convective resistance decreases (~2 × 10-3 m2 K/W), and the lower contact resistance of the thermally sprayed heat exchanger provides better performance than the brazed heat exchangers.
Numerical heat transfer studies of the fatty acids for different heat exchanger materials on the performance of a latent heat storage system
Energy Technology Data Exchange (ETDEWEB)
Atul Sharma; Lee Dong Won; Jun Un Park [Korea Institute of Energy Research, Daejeon (Korea). Solar Thermal Research Centre; Buddhi, D. [Devi Ahilya University, Indore (India). Thermal Energy Storage Laboratory
Theoretical investigations of fatty acids as a phase change material (PCM) for energy storage system have been conducted in this study. The selected fatty acids were capric acid, lauric acid, myristic acid, palmitic acid and stearic acid. For the two-dimensional simulation model based on the enthalpy approach, calculations have been made for the melt fraction with conduction only. Glass, stainless steel, tin, aluminium mixed, aluminium and copper were used as heat exchanger materials in the numerical calculations. Theoretical results show that capric acid was found good compatibility with latent heat storage system. The large value of thermal conductivity of heat exchanger materials did not make significant contribution on the melt fraction. (author)
Modeling the dynamic operation of a small fin plate heat exchanger – parametric analysis
Directory of Open Access Journals (Sweden)
Motyliński Konrad
Full Text Available Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700–900 °C is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the
Modeling the dynamic operation of a small fin plate heat exchanger - parametric analysis
Motyliński, Konrad; Kupecki, Jakub
Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700-900 °C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides
Heat exchanger inventory cost optimization for power cycles with one feedwater heater
International Nuclear Information System (INIS)
Highlights: • Cost optimization of heat exchanger inventory in power cycles is investigated. • Analysis for an endoreversible power cycle with an open feedwater heater is shown. • Different constraints on the power cycle are investigated. • The constant heat addition scenario resulted in the lowest value of the cost function. - Abstract: Cost optimization of heat exchanger inventory in power cycles with one open feedwater heater is undertaken. In this regard, thermoeconomic analysis for an endoreversible power cycle with an open feedwater heater is shown. The scenarios of constant heat rejection and addition rates, power as well as rate of heat transfer in the open feedwater heater are studied. All cost functions displayed minima with respect to the high-side absolute temperature ratio (θ1). In this case, the effect of the Carnot temperature ratio (Φ1), absolute temperature ratio (ξ) and the phase-change absolute temperature ratio for the feedwater heater (Φ2) are qualitatively the same. Furthermore, the constant heat addition scenario resulted in the lowest value of the cost function. For variation of all cost functions, the smaller the value of the phase-change absolute temperature ratio for the feedwater heater (Φ2), lower the cost at the minima. As feedwater heater to hot end unit cost ratio decreases, the minimum total conductance required increases
Fabrication of a tantalum neutral source heat exchanger
International Nuclear Information System (INIS)
The fabrication and testing of the Neutral Source Heat Exchanger (NSHE), a device required for a plutonium isotope separation pilot plant are described. The unit is a circular water-cooled tantalum plate which will have plutonium cast onto it. After the plutonium is cast and machined to final shape, the assembly will serve as a sputtering substrate for the separation process. The cooling water flow path is unique (adjacent logarithmic spirals terminating 180 degress apart) and created several fabrication and testing challenges. A photograph of the lower plate, showing the water channel geometry and brazing filler material, is shown
Aging management guideline for commercial nuclear power plants - heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Booker, S.; Lehnert, D.; Daavettila, N.; Palop, E.
This Aging Management Guideline (AMG) describes recommended methods for effective detection and mitigation of age-related degradation mechanisms in commercial nuclear power plant heat exchangers important to license renewal. The intent of this AMG is to assist plant maintenance and operations personnel in maximizing the safe, useful life of these components. It also supports the documentation of effective aging management programs required under the License Renewal Rule 10 CFR 54. This AMG is presented in a manner that allows personnel responsible for performance analysis and maintenance to compare their plant-specific aging mechanisms (expected or already experienced) and aging management program activities to the more generic results and recommendations presented herein.
Aging management guideline for commercial nuclear power plants - heat exchangers
International Nuclear Information System (INIS)
This Aging Management Guideline (AMG) describes recommended methods for effective detection and mitigation of age-related degradation mechanisms in commercial nuclear power plant heat exchangers important to license renewal. The intent of this AMG is to assist plant maintenance and operations personnel in maximizing the safe, useful life of these components. It also supports the documentation of effective aging management programs required under the License Renewal Rule 10 CFR 54. This AMG is presented in a manner that allows personnel responsible for performance analysis and maintenance to compare their plant-specific aging mechanisms (expected or already experienced) and aging management program activities to the more generic results and recommendations presented herein
Permeation Barrier Coatings for the Helical Heat Exchanger
International Nuclear Information System (INIS)
A permeation barrier coating was specified for the Helical Heat Exchanger (HHE) to minimize contamination through emissions and/or permeation into the nitrogen system for ALARA reasons. Due to the geometry of the HHE, a special coating practice was needed since the conventional method of high temperature pack aluminization was intractable. A survey of many coating companies was undertaken; their coating capabilities and technologies were assessed and compared to WSRC needs. The processes and limitations to coating the HHE are described. Slurry coating appears to be the most technically sound approach for coating the HHE
Numerical simulation of two phase flows in heat exchangers
International Nuclear Information System (INIS)
The author gives an overview of his research activity since 1981. He first gives a detailed presentation of properties and equations of two-phase flows in heat exchangers, and of their mathematical and numerical investigation: semi-local equations (mass conservation, momentum conservation and energy conservation), homogenized conservation equations (mass, momentum and enthalpy conservation, boundary conditions), equation closures, discretization, resolution algorithm, computational aspects and applications. Then, he reports the works performed in the field of turbulent flows, hyperbolic methods, low Mach methods, the Neptune project, and parallel computing
Vapor Compression and Thermoelectric Heat Pump Heat Exchangers for a Condensate Distillation System: Design and Experiment
Erickson, Lisa R.; Ungar, Eugene K.
Maximizing the reuse of wastewater while minimizing the use of consumables is critical in long duration space exploration. One of the more promising methods of reclaiming urine is the distillation/condensation process used in the cascade distillation system (CDS). This system accepts a mixture of urine and toxic stabilizing agents, heats it to vaporize the water and condenses and cools the resulting water vapor. The CDS wastewater flow requires heating and its condensate flow requires cooling. Performing the heating and cooling processes separately requires two separate units, each of which would require large amounts of electrical power. By heating the wastewater and cooling the condensate in a single heat pump unit, mass, volume, and power efficiencies can be obtained. The present work describes and compares two competing heat pump methodologies that meet the needs of the CDS: 1) a series of mini compressor vapor compression cycles and 2) a thermoelectric heat exchanger. In the paper, the system level requirements are outlined, the designs of the two heat pumps are described in detail, and the results of heat pump performance tests are provided. A summary is provided of the heat pump mass, volume and power trades and a selection recommendation is made.
A thermoelectric power generating heat exchanger: Part I - Experimental realization
Bjørk, R; Pryds, N; Lindeburg, N; Viereck, P
An experimental realization of a heat exchanger with commercial thermoelectric generators (TEGs) is presented. The power producing capabilities as a function of flow rate and temperature span are characterized for two different commercial heat transfer fluids and for three different thermal interface materials. The device is shown to produce 2 W per TEG or 0.22 W cm$^{-2}$ at a fluid temperature difference of 175 $^\\circ$C and a flow rate per fluid channel of 5 L min$^{-1}$. One experimentally realized design produced 200 W in total from 100 TEGs. For the design considered here, the power production is shown to depend more critically on the fluid temperature span than on the fluid flow rate. Finally, the temperature span across the TEG is shown to be 55% to 75% of the temperature span between the hot and cold fluids.
Properties of Alloy 617 for Heat Exchanger Design
Energy Technology Data Exchange (ETDEWEB)
Wright, Richard Neil [Idaho National Laboratory; Carroll, Laura Jill [Idaho National Laboratory; Benz, Julian Karl [Idaho National Laboratory; Wright, Julie Knibloe [Idaho National Laboratory; Lillo, Thomas Martin [Idaho National Laboratory; Lybeck, Nancy Jean [Idaho National Laboratory
Abstract – Alloy 617 is among the primary candidates for very high temperature reactor heat exchangers anticipated for use up to 950ºC. Elevated temperature properties of this alloy and the mechanisms responsible for the observed tensile, creep and creep-fatigue behavior have been characterized over a wide range of test temperatures up to 1000ºC. Properties from the current experimental program have been combined with archival information from previous VHTR research to provide large data sets for many heats of material, product forms, and weldments. The combined data have been analyzed to determine conservative values of yield and tensile strength, strain rate sensitivity, creep-rupture behavior, fatigue and creep- fatigue properties that can be used for engineering design of reactor components. Phenomenological models have been developed to bound the regions over which the engineering properties are well known or can be confidently extrapolated for use in design.
Study of thermal energy storage using fluidized bed heat exchangers
Weast, T. E.; Shannon, L. J.; Ananth, K. P.
The technical and economic feasibility of fluid bed heat exchangers (FBHX) for thermal energy storage (TES) in waste heat recovery applications is assessed by analysis of two selected conceptual systems, the rotary cement kiln and the electric arc furnace. It is shown that the inclusion of TES in the energy recovery system requires that the difference in off-peak and on-peak energy rates be large enough so that the value of the recovered energy exceeds the value of the stored energy by a wide enough margin to offset parasitic power and thermal losses. Escalation of on-peak energy rates due to fuel shortages could make the FBHX/TES applications economically attractive in the future.
Measuring important parameters for air-sea heat exchange
Garbe, Christoph; Schimpf, Uwe; Jaehne, Bernd
The heat transfer between the ocean and the atmosphere is one of the most important parameters governing the global climate. Important parameters include the heat transfer velocity and the net heat flux as well as parameters of the underlying transport model. However, the net heat flux is hard to measure since processes take place in the thermal boundary layer, that is the topmost layer of the ocean less than 1 mm thick. Current techniques rely on three independent measurements of the constituent fluxes, the sensible heat flux, latent heat flux and radiative flux. They depend on indirect measurements of meteorological parameters and rely on a combination of data from different sensors using a number of heuristic assumptions. High relative errors and the need for long temporal averaging reduce the practicability of these techniques. In this paper a novel technique is presented that circumvents these drawbacks by directly measuring the net heat flux across the air-water interface with a single low-NETD infrared camera. A newly developed digital image processing technique allows to simultaneously estimating the surface velocity field and parameters of the temporal temperature change. In particular, this technique allows estimating the total derivative of the temperature with respect to time from a sequence of infrared images, together with error bounds on the estimates. This derivative can be used to compute the heat flux density and the heat transfer velocity, as well as the probability density function of the underlying surface renewal model. It is also possible to estimate the bulk-skin temperature difference given rise to by the net heat flux. Our technique has been successfully used in both laboratory measurements in the Heidelberg Aeolotron, as well as in field measurements in the equatorial pacific during the NOAA GasExII experiment this spring. The data show that heat flux measurements to an accuracy of better than 5% on a time scale of seconds are feasible.
Design and simulation of heat exchangers using Aspen HYSYS, and Aspen exchanger design and rating for paddy drying application
Janaun, J.; Kamin, N. H.; Wong, K. H.; Tham, H. J.; Kong, V. V.; Farajpourlar, M.
Air heating unit is one of the most important parts in paddy drying to ensure the efficiency of a drying process. In addition, an optimized air heating unit does not only promise a good paddy quality, but also save more for the operating cost. This study determined the suitable and best specifications heating unit to heat air for paddy drying in the LAMB dryer. In this study, Aspen HYSYS v7.3 was used to obtain the minimum flow rate of hot water needed. The resulting data obtained from Aspen HYSYS v7.3 were used in Aspen Exchanger Design and Rating (EDR) to generate heat exchanger design and costs. The designs include shell and tubes and plate heat exchanger. The heat exchanger was designed in order to produce various drying temperatures of 40, 50, 60 and 70°C of air with different flow rate, 300, 2500 and 5000 LPM. The optimum condition for the heat exchanger were found to be plate heat exchanger with 0.6 mm plate thickness, 198.75 mm plate width, 554.8 mm plate length and 11 numbers of plates operating at 5000 LPM air flow rate.
Numerical Analysis for Heat Transfer Characteristics of Elliptic Fin-Tube Heat Exchanger with Various Shapes
Energy Technology Data Exchange (ETDEWEB)
Yoo, Jae Hwan; Yoon, Jun Kyu [Gachon Univ., Seongnam (Korea, Republic of)
In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (A R), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CAD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1.5 m/s. RCM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the A R and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type.
A novel experimental setup with sand trunk for heat extraction of geothermal heat exchanger
Institute of Scientific and Technical Information of China (English)
JIANG Yi-qiang; YAO Yang; CHEN Yi-ming; MA Zui-liang
A novel experimental setup was developed to study the heat extraction of geothermal heat exchanger (GHE) in different operational modes under adiabatic and isothermal boundaries. The experimental setup con-sists of a sand trunk, a tailored water chiller, a natural cold source unit, two water boxes containing hot water and cool water, and a data acquisition system. The experimental results indicate that the volume flow rate of the entering water is a main factor affecting the heat extraction; furthermore, the heat extraction value per meter pipe decreases gradually along the heat extraction pipe and increases with the increase of the incoming water volume flow rate. Therefore, this novel experimental setup may be helpful to further study the operation per-formance of GHE in different types of soil.
Numerical Simulation of Heat Transfer Characteristics of Horizontal Ground Heat Exchanger in Frozen Soil Layer
Institute of Scientific and Technical Information of China (English)
A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil's moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil's moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard "Technical Code for Ground Source Heat Pump (GB 50366-2005)" is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil's structure, backfilled materials,weather data, and economic analysis.
Solution of operational problems utilization of an EX-IRT-2000 heat exchanger
International Nuclear Information System (INIS)
The Bandung TRIGA Mark II Reactor has been successfully operated for 21 years, especially in low power operation or as neutron sources for various experiments. Most of the operating time, approximately 80% of routine operation, was dedicated for radio-isotope production. During routine operation for radio-isotope production, the reactor could not be operated at full power. The reactor was operated at 60% of the maximum power (1 MWth) due to the inability of the original heat exchanger to operate properly. The reason is that slack deposition was built-up on the secondary side of the heat exchanger. Therefore, it reduced the coefficient of heat transfer considerably. To solve the problems, a set of heat exchanger including the pump was installed In parallel with the original unit. The heat exchanger was an IRT-2000 Reactor Heat exchanger which was collected from the abandoned IRT-2000 Project. The heat exchanger has capacity of 1.25 MW. The new heat exchanger could reduced the outlet temperature of the primary coolant Into 42 deg. C. While the original-heat exchanger at the worst condition and at 600 kW of power reach outlet temperature 49 deg. C. The IRT Heat Exchanger is a counter flow heat exchanger. (author)
Nordic exchange of students and climate change.
Thomsson, A.
Since the end of 2010 and until the summer of 2011 two upper secondary schools in Höyanger, Norway and Ronneby, Sweden had the possibility to take part in a project called Nordplus junior. The main aims of the program are: • To promote Nordic languages and culture and mutual Nordic-Baltic linguistic and cultural understanding. • To contribute to the development of quality and innovation in the educational systems for life-long learning in the participating countries by means of educational cooperation, development projects, exchanges and networking. • To support, develop, draw benefit from and spread innovative products and processes in education through systematic exchange of experiences and best practice. • To strengthen and develop Nordic educational cooperation and contribute to the establishment of a Nordic-Baltic educational area. The students did research on climate change and the impact on local and regional areas. Many questions had to be answered, giving an explanation to what happens if the climate changes. Questions related to Höyanger, Norway What happens to life in Norwegian fiords? Which attitudes do youngsters and adults have about climate change and what actions do they take? What does a rise in sea level mean for Höyanger? How are different tourist attractions affected in western Norway? Questions related to Ronneby, Sweden How is the regional fauna and flora affected? What will happen to agriculture and forestry? What do adults and youngsters know about consequences of a possible climate change? What happens to the people of Ronneby if the sea level rises? Are there any positive outcomes if the climate changes? Conclusions In Norwegian fiords there could be benefits because fish are growing faster in the winter because of an increased temperature. At the same time there could be an imbalance in the ecosystem because of a change in the living ranges of different species. Most of the young boys and girls in Höyanger, Norway were
Performance analysis of cylindrical metal hydride beds with various heat exchange options
International Nuclear Information System (INIS)
Highlights: • 3D numerical model for the comparison of H2 uptake performances in MH reactors. • 4 options of heat exchange between heat transfer fluid and MH in cylindrical reactor compared. • Straight tube internal heat exchanger. • Helical coil internal heat exchanger. • External heat exchange without and with transversal fins in the MH reactor. - Abstract: A 3D numerical heat-and-mass transfer model was used for the comparison of H2 uptake performances of powdered cylindrical MH beds comprising MmNi4.6Al0.4 hydrogen storage material. The considered options of heat exchange between the MH and a heat transfer fluid included internal cooling using straight (I) or helically coiled (II) tubing, as well as external cooling of the MH bed without (III) and with (IV) transversal fins. The dynamic performances of these layouts were compared based on the numerical simulation. The effect of heat transfer coefficient was also analysed
Thermal performance of direct contact heat exchangers for mixed hydrocarbons
Energy Technology Data Exchange (ETDEWEB)
Sharpe, L. Jr.; Coswami, D.Y.; Demuth, O.J.; Mines, G.
This paper describes a physical and a mathematical model for evaluating the tray efficiencies for a direct contact heat exchanger (DCHX). The model is then used to determine the efficiencies for tests conducted on a 60kW sieve tray DCHX as heat is transferred from a geofluid (brine) to a working fluid (mixed hydrocarbons). It is assumed that there are three distinct regions in the column based on the state of the working fluid, as follows: Region I - Preheating with no vaporization; Region II - Preheating with moderate vaporization; and Region III - Major vaporization. The boundaries of these regions can be determined from the experimental data. In the model, mass balance and energy balance is written for a tray ''N'' in each of these regions. Finally, the ''tray efficiency'' or ''heat transfer'' effectiveness of the tray is calculated based on the definition that it is the ratio of the actual heat transfer to the maximum possible, thermodynamically.
V. A. Lapin; V. N. Melkumov; A. N. Kobelev
The mathematical model of heat transfer in vortex heat exchanger using natural gas energy which is released under decompression in gas-main pipe-lines for consumers of gas supply systems (dwellings, public and industrial buildings).
Directory of Open Access Journals (Sweden)
V. A. Lapin
Full Text Available The mathematical model of heat transfer in vortex heat exchanger using natural gas energy which is released under decompression in gas-main pipe-lines for consumers of gas supply systems (dwellings, public and industrial buildings.
Exporter Price Response to Exchange Rate Changes
DEFF Research Database (Denmark)
Fosse, Henrik Barslund
Firms exporting to foreign markets face a particular challenge: to price their exports in a foreign market when the exchange rate changes. This paper takes on pricing- to-market using a unique data set that covers rm level monthly trade at great detail. As opposed to annual trade ows, monthly trade...... ows bring us closer to the transaction level where rm decisions are actually made. I nd that the utilization of monthly data does add new information about the average level of pricing-to-market, and the di¤erences between long-run pricing-to-market and short-run pricing-to-market. Furthermore, I nd...... industry di¤erences in pricing-to-market in terms of the magnitude (zero to complete pricing-to-market) and the timing (when do rms changes prices), and that pricing-to-market is stronger on high-income markets. As discussed in detail in the paper, all results are in-line with predictions of several...
A novel method to improve the performance of heat exchanger--Temperature fields coordination of fluids
Institute of Scientific and Technical Information of China (English)
GUO Zengyuan; WEI Shu; CHENG Xinguang
The methods to enhance the heat transfer in heat exchanger may be classified into two levels: one is to improve the heat transfer coefficient; the other is to upgrade the whole arrangement of the heat exchangers. For the second level, the performance of heat exchanger can be upgraded by increasing the coordination degree between the temperature fields of cold and hot fluids. When the temperature distributions are similar to each other, the temperature difference field (TDF) is more uniform, which means that the temperature fields are more coordinated with each other. For the cross-flow heat exchanger, rearrangement of the heat exchange surface area should improve the heat transfer effectiveness, which is even equal to that of the counter-flow heat exchanger when the surface area is reassigned optimally. For the multi-stream heat exchanger, the thermal performance is also dependent on the uniformity of the TDF, and the parallel-flow arrangement may achieve higher heat exchange effectiveness than the counter-flow arrangement, which indicates that the performance of heat exchanger depends on the coordination degree of temperature fields instead of the flow arrangement.
Integrated heat exchanger design for a cryogenic storage tank
Energy Technology Data Exchange (ETDEWEB)
Fesmire, J. E.; Bonner, T.; Oliveira, J. M.; Johnson, W. L.; Notardonato, W. U. [NASA Kennedy Space Center, Cryogenics Test Laboratory, NE-F6, KSC, FL 32899 (United States); Tomsik, T. M. [NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135 (United States); Conyers, H. J. [NASA Stennis Space Center, Building 3225, SSC, MS 39529 (United States)
Field demonstrations of liquid hydrogen technology will be undertaken for the proliferation of advanced methods and applications in the use of cryofuels. Advancements in the use of cryofuels for transportation on Earth, from Earth, or in space are envisioned for automobiles, aircraft, rockets, and spacecraft. These advancements rely on practical ways of storage, transfer, and handling of liquid hydrogen. Focusing on storage, an integrated heat exchanger system has been designed for incorporation with an existing storage tank and a reverse Brayton cycle helium refrigerator of capacity 850 watts at 20 K. The storage tank is a 125,000-liter capacity horizontal cylindrical tank, with vacuum jacket and multilayer insulation, and a small 0.6-meter diameter manway opening. Addressed are the specific design challenges associated with the small opening, complete modularity, pressure systems re-certification for lower temperature and pressure service associated with hydrogen densification, and a large 8:1 length-to-diameter ratio for distribution of the cryogenic refrigeration. The approach, problem solving, and system design and analysis for integrated heat exchanger are detailed and discussed. Implications for future space launch facilities are also identified. The objective of the field demonstration will be to test various zero-loss and densified cryofuel handling concepts for future transportation applications.
Manufacture of power station heat exchangers using modern production technology
International Nuclear Information System (INIS)
Heat exchangers of high quality and operational safety can only be fabricated economically if fabrication is as 'simple' as possible and can be controlled and if, through value analysis, the work flows can be mechanized and automated and the following requirements are met: use of materials that are easy to work with for the application considered, choice of product designs and wall thicknesses that offer favourable conditions for processing and non-destructive testing, placing of seams in such a way that good accessibility for welding and minimum residual welding stresses are assured, minimizing the number of welding seams, use of automatic welding machines for submerged-arc welding and electronically controlled sources of welding current - semi-automatic equipment for spatter-free interfaces (pulse technique), electronically controlled equipment for welding in rollers and pipes and CNC-controlled machining centres for drilling pipe galleries (deep-hole drilling) and baffle plates and for machining the sealing elements after welding. Continuous inspections in each phase of fabrication assures that heat exchangers are made which fully meet the requirements of nuclear power station operators. (orig.)
Integrated heat exchanger design for a cryogenic storage tank
Fesmire, J. E.; Tomsik, T. M.; Bonner, T.; Oliveira, J. M.; Conyers, H. J.; Johnson, W. L.; Notardonato, W. U.
Field demonstrations of liquid hydrogen technology will be undertaken for the proliferation of advanced methods and applications in the use of cryofuels. Advancements in the use of cryofuels for transportation on Earth, from Earth, or in space are envisioned for automobiles, aircraft, rockets, and spacecraft. These advancements rely on practical ways of storage, transfer, and handling of liquid hydrogen. Focusing on storage, an integrated heat exchanger system has been designed for incorporation with an existing storage tank and a reverse Brayton cycle helium refrigerator of capacity 850 watts at 20 K. The storage tank is a 125,000-liter capacity horizontal cylindrical tank, with vacuum jacket and multilayer insulation, and a small 0.6-meter diameter manway opening. Addressed are the specific design challenges associated with the small opening, complete modularity, pressure systems re-certification for lower temperature and pressure service associated with hydrogen densification, and a large 8:1 length-to-diameter ratio for distribution of the cryogenic refrigeration. The approach, problem solving, and system design and analysis for integrated heat exchanger are detailed and discussed. Implications for future space launch facilities are also identified. The objective of the field demonstration will be to test various zero-loss and densified cryofuel handling concepts for future transportation applications.
Directory of Open Access Journals (Sweden)
Zeki ARGUNHAN
Full Text Available This paper examines the effect of turbulance creators on heat transfer and pressure drop used in concentric heat exchanger experimentaly. Heat exchanger has an inlet tube with 60 mm in diameter. The angle of swirl generators wings is 55º with each wing which has single, double, three and four holes. Swirl generators is designed to easily set to heat exchanger entrance. Air is passing through inner tube of heat exhanger as hot fluid and water is passing outer of inner tube as cool fluid.
ARGUNHAN, Zeki; Yildiz, Cengiz
This paper examines the effect of turbulance creators on heat transfer and pressure drop used in concentric heat exchanger experimentaly. Heat exchanger has an inlet tube with 60 mm in diameter. The angle of swirl generators wings is 55º with each wing which has single, double, three and four holes. Swirl generators is designed to easily set to heat exchanger entrance. Air is passing through inner tube of heat exhanger as hot fluid and water is passing outer of inner tube as cool fluid.
P. MOHAJERI KHAMENEH,; I. MIRZAIE,; N. POURMAHMOUD; M.RAHIMI EOSBOEE; S. MAJIDYFAR; Mansoor, M.
Three dimensional simulations of the single-phase laminar flow and forced convective heat transfer of water in round tube and straight microchannel heat exchangers were investigated numerically. This numerical method was developed to measure heat transfer parameters of round tube and straight microchannel tube geometries. Then, similarities and differences were compared between different geometries. The geometries and operating conditions of those indicated heat exchangers were created using ...
Heat transfer processes in parallel-plate heat exchangers of thermoacoustic devices – numerical and experimental approaches
Artur J. Jaworski; Piccolo, Antonio
This paper addresses the issues of heat transfer in oscillatory flow conditions, which are typically found in thermoacoustic devices. The analysis presented concerns processes taking place in the individual "channels" of the parallel-plate heat exchangers (HX), and is a mixture of experimental and numerical approaches. In the experimental part, the paper describes the design of experimental apparatus to study the thermal-fluid processes controlling heat transfer in thermoacoustic heat exchang...
Effect of Twisted-Tape Turbulators and Nanofluid on Heat Transfer in a Double Pipe Heat Exchanger
Directory of Open Access Journals (Sweden)
Heydar Maddah
Full Text Available Heat transfer and overall heat transfer in a double pipe heat exchanger fitted with twisted-tape elements and titanium dioxide nanofluid were studied experimentally. The inner and outer diameters of the inner tube were 8 and 16 mm, respectively, and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made from aluminum sheet with tape thickness (d of 1 mm, width (W of 5 mm, and length of 120 cm. Titanium dioxide nanoparticles with a diameter of 30 nm and a volume concentration of 0.01% (v/v were prepared. The effects of temperature, mass flow rate, and concentration of nanoparticles on the overall heat transfer coefficient, heat transfer changes in the turbulent flow regime Re≥2300, and counter current flow were investigated. When using twisted tape and nanofluid, heat transfer coefficient was about 10 to 25 percent higher than when they were not used. It was also observed that the heat transfer coefficient increases with operating temperature and mass flow rate. The experimental results also showed that 0.01% TiO2/water nanofluid with twisted tape has slightly higher friction factor and pressure drop when compared to 0.01% TiO2/water nanofluid without twisted tape. The empirical correlations proposed for friction factor are in good agreement with the experimental data.
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Hansen, B J; Klebaner, A; 10.1063/1.4706971
Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger ...
Copper metal foam as an essential construction element of innovative heat exchanger
Directory of Open Access Journals (Sweden)
R. Rybár
Full Text Available Paper deals with creation of the innovative heat exchanger - manifold header for the heat pipe evacuated tube solar collector, which essential functional element is heat exchange chamber made of the copper metal foam. Design of the heat exchanger is based on effective utilization of the unique properties of the metal foam which makes it possible to design highly effective and space saving devices. Inner volume of heat exchanger was reducing from 0,00045 m3 to 0,000135 m3 and heat exchange surface was increase from 0,0104 m2 to 0,1403 m2 at proposed prototype, what drastically increase heat exchange efficiency. The proposal itself is based on the unique physical properties of the metal foam, which was described by computational analysis.
Continuation of Studies on Development of ODS Heat Exchanger Tubing
Energy Technology Data Exchange (ETDEWEB)
Lawrence Brown; David Workman; Bimal Kad; Gaylord Smith; Archie Robertson; Ian Wright
The Department of Energy (DOE), National Energy Technology Center (NETL), has initiated a strategic plan for the development of advanced technologies needed to design and build fossil fuel plants with very high efficiency and environmental performance. These plants, referred to as 'Vision 21' and FutureGen programs by DOE, will produce electricity, chemicals, fuels, or a combination of these products, and possibly secondary products such as steam/heat for industrial use. MA956 is a prime candidate material being considered for a high temperature heat exchanger in the 'Vision 21' and FutureGen programs. This material is an oxide dispersion strengthened (ODS) alloy; however, there are some gaps in the data required to commit to the use of these alloys in a full-size plant. To fill the technology gaps for commercial production and use of the material for 'Advanced Power Generation Systems' this project has performed development activity to significant increase in circumferential strength of MA956 as compared to currently available material, investigated bonding technologies for bonding tube-to-tube joints through joining development, and performed tensile, creep and fire-side corrosion tests to validate the use and fabrication processes of MA956 to heat exchanger tubing applications. Development activities within this projected has demonstrated increased circumferential strength of MA956 tubes through flow form processing. Of the six fabrication technologies for bonding tube-to-tube joints, inertia friction welding (IFW) and flash butt welding (FBW) were identified as processes for joining MA956 tubes. Tensile, creep, and fire-side corrosion test data were generated for both base metal and weld joints. The data can be used for design of future systems employing MA956. Based upon the positive development activities, two test probes were designed and fabricated for field exposure testing at 1204 C ({approx}2200 F) flue gas. The probes
Numerical Modeling of Freezing and Melting Processes around a Borehole Heat Exchanger
Shao, Haibing; Zheng, Tianyuan; Nagel, Thomas; Kolditz, Olaf
In ground sourced heat pump (GSHP) systems, heat energy stored in the shallow subsurface is extracted through borehole heat exchangers (BHE) and then utilized for domestic heating. In cold regions, the continuous heat deficit in the vicinity of the BHE can cause freezing of the surrounding soil. Its material properties, such as permeability and heat conductivity, will then significantly change and lead to a series of coupled thermal, hydraulic, and mechanical processes. In particular, the heat exchange performance of the BHE will be altered, and the frozen soil may also induce ground lift or subsidence in the vicinity of the building. As the first step of modelling this coupled system, we followed the approach proposed by Al-Khoury et al (2010) and Diersch et al (2011), where the BHE has been fully integrated into the numerical model in a dual-continuum way. Additionally, we extended the existing heat transport module in the numerical simulator OpenGeoSys to include the freezing and melting processes, whereas the ice volume fraction in the soil is non-linearly dependent on the temperature, and the soil properties were determined based on the degree of freezing/melting. The non-linearity of the coupled model was numerically solved by a Newton scheme. The extended model has been verified by comparing numerical results against analytical solutions and also findings from other numerical codes. Moreover, we proposed and simulated a hypothetical scenario, where ice is gradually forming around a BHE in response to the continuous operation of a heat pump. The model is capable of reproducing the thermodynamic freezing process as well as the heat transport affected by it. Future work will be focused on the integration of deformation processes into the model.
A simple and accurate numerical network flow model for bionic micro heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Pieper, M.; Klein, P. [Fraunhofer Institute (ITWM), Kaiserslautern (Germany)
Heat exchangers are often associated with drawbacks like a large pressure drop or a non-uniform flow distribution. Recent research shows that bionic structures can provide possible improvements. We considered a set of such structures that were designed with M. Hermann's FracTherm {sup registered} algorithm. In order to optimize and compare them with conventional heat exchangers, we developed a numerical method to determine their performance. We simulated the flow in the heat exchanger applying a network model and coupled these results with a finite volume method to determine the heat distribution in the heat exchanger. (orig.)
Numerical characterization of heat transfer in closed-loop vertical ground heat exchanger
Institute of Scientific and Technical Information of China (English)
Chulho; LEE; Hujeong; GIL; Hangseok; CHOI; Shin-Hyung; KANG
A series of numerical analyses has been performed on the characteristics of heat transfer in a closed-loop vertical ground heat exchanger(U-loop).A 2-D finite element analysis was conducted to evaluate the temperature distribution over the cross section of the U-loop system involving high-density polyethylene(HDPE) pipe/grout/soil to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system,which is equipped with a thermally insulating lattice in order to reduce thermal interference between the inlet and outlet pipes.In addition,a 3-D finite volume analysis(FLUENT) was adopted to simulate the operation of the closed-loop vertical ground heat exchanger with the consideration of the effect of a distance between the inlet and outlet pipes,grout's thermal properties,the effectiveness of the latticed HDPE pipe system,and the rate of circulation pump.It was observed that the thermal interference between the two strands of U-loop is of importance in enhancing efficiency of the ground heat exchanger.Consequently,it is recommended to modify the configuration of the conventional U-loop system by equipping the thermally insulating lattice between the two pipe strands.
Ventilation Heat Recovery from Wood-Burning Domestic Flues. A Theoretical Analysis Based on a Triple Concentric Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
Lionel Druette
Full Text Available This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed.
Geothermal direct-contact heat exchange. Final report
Energy Technology Data Exchange (ETDEWEB)
Sims, A.V.
A glass direct contact heat exchange column was operated in the laboratory at atmospheric pressure using hot water and normal hexane. Column internals tested included an empty column, sieve trays, disk-and-doughnut trays, and two types of packing. Operation was very smooth in all cases and the minimum temperature approaches varied from less than 1{sup 0}C for packing to 13{sup 0}C for the empty column. High heat transfer rates were obtained in all cases, however, columns should be sized on the basis of liquid and vapor traffic. The solubilities of hydrocarbons were determined for normal hexane, pentane and butane in water and sodium chloride and calcium chloride brines at various temperatures. The values seem to be internally consistent and salt content was found to depress hydrocabon solubility. Laboratory stripping tests showed that gas stripping can be used to remove hydrocarbon from reject hot water from the direct contact heat exchange column. Although the gas volumes required are small, stripping gas requirements cannot be accurately predicted without testing. A computer program was used to study the effect of operating variables on thermodynamic cycle efficiencies. Optimum efficiencies for the moderate brine conditions studied were obtained with isopentane as working fluid and relatively low operating pressure. A preliminary design for a 50 MWe plant was prepared and plant capital cost and operating cost were estimated. These costs were combined with previously developed brine production and power transmission costs to provide an estimate of the cost of delivered power for a geothermal field at Heber, California. A pilot plant program is described that would be suitable for continuing the investigation of the direct contact process in the field. The program includes a suggested schedule and the estimated cost.
Changes in pumpkin seed oil during heating
Lazos, Evangelos S.; Tsaknis, Jhon; Bante, Maria
Purified pumpkin seed oil was heated either continuously or intermittently for 10 hours at 180±5°C, and occurring changes were evaluated. Free fatty acids (FFA), peroxide value (PV), colour, polar compounds and viscosity increased, while iodine value and unsaturation decreased. Intermittent heating had the more pronounced effect on these changes. Fatty acid profile determination showed non-significant changes in palmitic (C16:0), arachidic (C20:0) and oleic (018:1) acids during heating. Stati...
Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger
International Nuclear Information System (INIS)
Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the 'Temperature Oscillation InfraRed Thermography' (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own
Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger
Grabenstein, V.; Kabelac, S.
Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the "Temperature Oscillation InfraRed Thermography" (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own
Control and prevention of ice formation and accretion on heat exchangers for ventilation systems
DEFF Research Database (Denmark)
Rahimi, Maral; Afshari, Alireza
In cold climates, the application of mechanical ventilation systems with heat recovery like are airto-air exchangers is used for reducing energy consumption for heating buildings by transferring heat exhausted air to supply air. However, increase efficiency of heat exchanger results in lower...... exhaust air temperatures and Ice formation on heat exchanger fins, which can cause problem and is not favourable. Therefore, prevention and control of ice formation on heat exchangers is necessary. The existing methods are divided into two different methods: active and passive ice control methods....... The active methods are e.g. bypass, recirculation, preheating. The passive methods relate to the surface characteristics of the heat exchanger fins as they have effect on ice formation in initial phase. All these methods have varying levels of success, cost, and effectiveness, which are depending on the heat...
Directory of Open Access Journals (Sweden)
R. Tuğrul OĞULATA
Full Text Available In this study, cross-flow plate type heat exchanger has been investigated because of its effective use in waste heat recovery systems. For this purpose, a heat regain system has been investigated and manufactured in laboratory conditions. Manufactured heat exchanger has been tested with an applicable experimental set up and temperatures, velocity of the air and the pressure losses occuring in the system have been measured and the efficiency of the system has been determined. The irreversibility of heat exchanger has been taken into consideration while the design of heat exchanger is being performed. So minimum entropy generation number has been analysied with respect to second law of thermodynamics in cross-flow heat exchanger. The minimum entropy generation number depends on parameters called optimum flow path length, dimensionless mass velocity and dimensionless heat transfer area. Variations of entropy generation number with these parameters have been analysied and introduced their graphics with their comments.
Positron annihilation lifetime study of Ag-ion exchanged and heat treated soda lime glass
International Nuclear Information System (INIS)
Slabs of soda lime silica glass (15% Na2O) were subjected to Ag+/Na+ ion exchange process and subsequent heat treatment. The change in glass structure and Ag states accompanied with these processes were studied using the positron annihilation lifetime spectroscopy. The positron annihilation lifetime measurements were performed with a fast-fast coincidence spectrometer employing a multi-parameter acquisition system. The lifetime parameters showed that the Ag+ ion reduction process takes place through two processes; the oxidation reduction reaction with Fe2+ impurities in the glass at heat treatment temperatures <500 deg. C, whereas at heat treatment ≥500 deg. C the reduction takes place through the polymerization reaction. The results also indicated that the heat treatment at 600 deg. C enhanced the formation of Ag metal nanoparticle crystals through the structural relaxation revealed by the free volume defects
Optimization of counterflow heat exchanger geometry through minimization of entropy generation
Lerou, P.P.P.M.; Veenstra, T.T.; Burger, J.F.; Brake, ter H.J.M.; Rogalla, H.
A counterflow heat exchanger (CFHX) is an essential element for recuperative cooling cycles. The performance of the CFHX strongly influences the overall performance of the cryocooler. In the design of a heat exchanger, different loss mechanisms like pressure drop and parasitic heat flows are often t
Comparative Study and Analysis between Helical Coil and Straight Tube Heat Exchanger
N. D. Shirgire; Amit Thakur
The purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger against a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is higher as compared to Straight tube due to their shape. Helical coils offer advantageous over straight tubes due to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a consequence of the curvature of the coil, which...
Down-Hole Heat Exchangers: Modelling of a Low-Enthalpy Geothermal System for District Heating
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M. Carlini
Full Text Available In order to face the growing energy demands, renewable energy sources can provide an alternative to fossil fuels. Thus, low-enthalpy geothermal plants may play a fundamental role in those areas—such as the Province of Viterbo—where shallow groundwater basins occur and conventional geothermal plants cannot be developed. This may lead to being fuelled by locally available sources. The aim of the present paper is to exploit the heat coming from a low-enthalpy geothermal system. The experimental plant consists in a down-hole heat exchanger for civil purposes and can supply thermal needs by district heating. An implementation in MATLAB environment is provided in order to develop a mathematical model. As a consequence, the amount of withdrawable heat can be successfully calculated.
Evaluation on performance of three-fluid and four-fluid heat exchangers
Soriano Alfonso, Héctor
In order to study the effectiveness of multi-fluid type heat exchangers, where more than two fluids are involved at the same time, three-fluid, four-fluid and double two-fluid heat exchangers have been studied using various methods. Using general definition of maximum heat transfer rate, which can be considered as a single definition of Qmax, the single effectiveness of multi-fluid heat exchangers can be developed. The maximum heat transfer rate (Qmax) depends on heat capacity ...
Heat transfer and combustion characteristics of a burner with a rotary regenerative heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Hirose, Yasuo; Kaji, Hitoshi; Arai, Norio
The authors have developed a Rotary Regenerative Combustion (RRX) System, which is coupled with a compact high efficiency regenerative air heat exchanger and a combustion burner. This system contributes to saving energy of fuel firing industrial furnaces and decreases NO{sub x} emission. This technology can be considered as a solution of greenhouse problem. This paper, discusses a compact high efficiency regenerative air heat exchanger in comparison with the existing types of regenerative burners and reverse firing with high momentum fuel jet (with motive fluid) in the furnace. This burner is compact in size, with high fuel efficiency, low NOx emission, easy to operate, and reliable, based on the results of field tests and commercial operations. The authors can say that the RRX system is a regenerative burner of the second generation.
Impact factors on the long-term sustainability of Borehole Heat Exchanger coupled Ground Source Heat Pump System
Shao, Haibing; Hein, Philipp; Görke, Uwe-Jens; Bucher, Anke; Kolditz, Olaf
In recent years, Ground Source Heat Pump System (GSHPS) has been recognized as an efficient technology to utilize shallow geothermal energy. Along with its wide application, some GSHPS are experiencing a gradual decrease in Borehole Heat Exchanger (BHE) outflow temperatures and thus have to be turned off after couple of years' operation. A comprehensive numerical investigation was then performed to model the flow and heat transport processes in and around the BHE, together with the dynamic change of heat pump efficiency. The model parameters were based on the soil temperature and surface weather condition in the Leipzig area. Different scenarios were modelled for a service life of 30 years, to reveal the evolution of BHE outflow and surrounding soil temperatures. It is found that lateral groundwater flow and using BHE for cooling will be beneficial to the energy recovery, along with the efficiency improvement of the heat pump. In comparison to other factors, the soil heat capacity and thermal conductivity are considered to have minor impact on the long-term sustainability of the system. Furthermore, the application of thermally enhanced grout material will improve the sustainability and efficiency. In contrast, it is very likely that undersized systems and improper grouting are the causes of strong system degradation.
Experiments and simulations on heat exchangers in thermoelectric generator for automotive application
International Nuclear Information System (INIS)
In this work, an energy-harvesting system which extracts heat from an automotive exhaust pipe and turns the heat into electricity by using thermoelectric power generators (TEGs) was built. Experiments show that the temperature difference in automotive system is not constant, especially the heat exchanger, which cannot provide the thermoelectric modules (TMs) large amount of heat. The thermal performance of different heat exchangers in exhaust-based TEGs is studied in this work, and the thermal characteristics of heat exchangers with different internal structures and thickness are discussed, to obtain higher interface temperature and thermal uniformity. Following computational fluid dynamics simulations, infrared experiments and output power testing system are carried out on a high-performance production engine with a dynamometer. Results show that a plate-shaped heat exchanger with chaos-shaped internal structure and thickness of 5 mm achieves a relatively ideal thermal performance, which is practically useful to enhance the thermal performance of the TEG, and larger total output power can be thus obtained. - Graphical abstract: The thermal and electrical characteristics of different heat exchangers of automotive exhaust-based thermoelectric generator are discussed, to obtain higher interface temperature and thermal uniformity. - Highlights: • Different internal structures and thickness of heat exchangers were proposed. • Power output testing system of the two heat exchangers was characterized. • Chaos-shaped heat exchanger (5 mm thickness) shows better performance
Development of inspection and repairing technology for FBR heat exchanger pipes
International Nuclear Information System (INIS)
A hybrid optical fiber scope and a laser processing head were combined with an eddy current testing unit for the inspection and repairing for Fast Breeder Reactor's heat exchanger pipes. The project proposes an effective cost reduction method for maintenance of FBR by extension of the heat exchanger's lifetime. By the end of March 2010, a prototype probing system for heat exchanger pipes will be completed. (author)
Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers
H. A. Navarro; L. C. Cabezas-Gómez
Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are ob...
Analytical Study on Thermal and Mechanical Design of Printed Circuit Heat Exchanger
Energy Technology Data Exchange (ETDEWEB)
Su-Jong Yoon; Piyush Sabharwall; Eung-Soo Kim
The analytical methodologies for the thermal design, mechanical design and cost estimation of printed circuit heat exchanger are presented in this study. In this study, three flow arrangements of parallel flow, countercurrent flow and crossflow are taken into account. For each flow arrangement, the analytical solution of temperature profile of heat exchanger is introduced. The size and cost of printed circuit heat exchangers for advanced small modular reactors, which employ various coolants such as sodium, molten salts, helium, and water, are also presented.
Entropy Generation in Periodic Regenerative Heat Exchanger due to Finite Temperature Difference
Pitchandi, K.; Natarajan, E.
This paper describes the second law of thermodynamics analysis of a regenerative heat exchanger. The analysis is based on the fact that the dimensionless parameters, known as the reduced periods and reduced length, are the characteristic variables to describe the heat exchanger. The solid matrix in the heat exchanger passage is discretized using trapezoidal rule and the elemental matrix is taken as a thermodynamic system. The second law of thermodynamics is applied to the system and the entro...
Heat Transfer and Pressure Drop Characteristics in Straight Microchannel of Printed Circuit Heat Exchangers
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Jang-Won Seo
Full Text Available Performance tests were carried out for a microchannel printed circuit heat exchanger (PCHE, which was fabricated with micro photo-etching and diffusion bonding technologies. The microchannel PCHE was tested for Reynolds numbers in the range of 100‒850 varying the hot-side inlet temperature between 40 °C–50 °C while keeping the cold-side temperature fixed at 20 °C. It was found that the average heat transfer rate and heat transfer performance of the countercurrrent configuration were 6.8% and 10%‒15% higher, respectively, than those of the parallel flow. The average heat transfer rate, heat transfer performance and pressure drop increased with increasing Reynolds number in all experiments. Increasing inlet temperature did not affect the heat transfer performance while it slightly decreased the pressure drop in the experimental range considered. Empirical correlations have been developed for the heat transfer coefficient and pressure drop factor as functions of the Reynolds number.
Estimation of pressure drop in gasket plate heat exchangers
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Neagu Anisoara Arleziana
Full Text Available In this paper, we present comparatively different methods of pressure drop calculation in the gasket plate heat exchangers (PHEs, using correlations recommended in literature on industrial data collected from a vegetable oil refinery. The goal of this study was to compare the results obtained with these correlations, in order to choose one or two for practical purpose of pumping power calculations. We concluded that pressure drop values calculated with Mulley relationship and Buonopane & Troupe correlation were close and also Bond's equation gave results pretty close to these but the pressure drop is slightly underestimated. Kumar correlation gave results far from all the others and its application will lead to oversize. In conclusion, for further calculations we will chose either the Mulley relationship or the Buonopane & Troupe correlation.
Experimental study and analysis of a novel multi-media plate heat exchanger
Institute of Scientific and Technical Information of China (English)
SONG JiWei; WANG Fei; CHENG Lin
The experimental study and analysis of a novel multi-media plate heat exchanger were performed in this paper.This novel multi-media plate heat exchanger was self-developed during the process of the investigation and design of the alpha magnetic spectrometer (AMS) thermal system.The plate of this kind of novel plate heat exchanger is formed by discontinuous structure wave consisting of convex sphere and concave sphere,its heat transfer performance is better than that of the BRI chevron plate heat exchanger,and its resistance characteristics are superior to those of the nornally used 60-degree plate heat exchanger.Furthermore,the mechanism analysis of heat transfer enhancement shows that the spherical wave structure can reduce the local field synergy angle,so as to improve the field synergy degree of velocity vector and temperature gradient vector.
Performance Evaluation of Plate-Fin-And Tube Heat Exchanger with Wavy Fins- A Review
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Sandip S. Kale
Full Text Available The plate fin-and-tube heat exchangers are widely used in variety of industrial applications, particularly in the heating, air-conditioning and refrigeration, HVAC industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. It is seen that the performance of heat exchangers can be greatly increased with the use of unconventionally shaped flow passages such as plain, perforated offset strip, louvered, wavy, vortex generator and pin. The current study is focused on wavy-fin. The wavy surface can lengthen the path of airflow and cause better airflow mixing. In order to design better heat exchangers and come up with efficient designs, a thorough understanding of the flow of air in these channels is required. Hence this study focuses on the heat transfer and friction characteristics of the air side for wavy fin and tube heat exchanger.
Thermal hydraulic parameter studies of heat exchanger for the TRIGA MARK II research reactor
International Nuclear Information System (INIS)
Thermal Hydraulic studies have being conducted at PUSPATI TRIGA Mark II (RTP) Nuclear Research Reactor. The purpose of this study is to determine the heat transfer characteristic and heat exchanger performance at difference reactor power. Fundamental concept and a plate type application of heat exchanger in RTP are presented in this study. A plate type heat exchanger is a device for RTP reactor cooling system built for efficient heat transfer from one fluid to another. The study involves the observation of inlet and outlet temperature profile, flow rate and pressure at the reactor pool and heat exchanger. The observed parameters are compared to basic engineering calculation and the output of the study has been beneficial to evaluate the performance of newly-installed plate type heat exchanger. (author)
Influence of baffle configurations on flow and heat transfer characteristics of trisection helical baffle heat exchangers
International Nuclear Information System (INIS)
Highlights: • Nephograms with velocity-vector superimposed are proposed on special slices. • Single vortex secondary flow and shortcut leakage patterns are clearly depicted. • Local heat transfer coefficient field and average value on tubes are presented. • Circumferential overlap scheme performs best over other schemes. - Abstract: Numerical simulation of flow and heat transfer characteristics in four trisection helical baffle heat exchangers with equilateral triangle tube layouts was conducted. The heat exchangers have the same helical pitch but four different baffle shapes or connections, i.e., a circumferential overlap (CO) scheme, an end-to-end (EE) scheme, a blocked V-notches (BV) scheme, and a middle axial overlap (MO) scheme. The single vortex secondary flow in each helical cycle and the leakage flow patterns in the V-notches of the adjacent baffles of these schemes are clearly depicted on the meridian slices and unfolded hexagon slices. The results for nine tubes in a 60° sector and four tube layers reveal that the local heat transfer coefficient of the center tube is much higher than that of the other tubes for all the schemes. The results show that the CO scheme has the highest shell-side heat transfer coefficient and comprehensive indexes, the BV scheme has the highest pressure drop and the worst comprehensive indexes, and the MO scheme has the lowest values of both shell-side heat transfer coefficient and pressure drop and the second highest comprehensive indexes. The average values of comprehensive index ho/Δpo of CO scheme in the calculated range is respectively 16.5%, 27.3% and 13.5% higher than that of the EE, BV and MO schemes
Optimal design of a NGNP heat exchanger with cost model
International Nuclear Information System (INIS)
With steady increase in energy consumption, the vulnerability of the fossil fuel supply, and environmental concerns, the U.S. Department of Energy (DOE) has initiated the Next Generation Nuclear Power Plants (NGNP), also known as Very High Temperature Reactor (VHTR). The VHTR is planned to be operational by 2021 with possible demonstration of a hydrogen generating plant. Various engineering design studies on both the reactor plant and energy conversion system are underway. For this and related Generation IV plants, it is the goal to not only meet safety criteria but to also be efficient, economically competitive, and environmentally friendly (proliferation resistant). Traditionally, heat exchanger (HX) design is based on two main approaches: Log-Mean Temperature Difference (LMTD) and effectiveness-NTU (ε-NTU). These methods yield the dimension of the HX under anticipate condition and vice-versa. However, one is not assured that the dimension calculated give the best performing HX when economics are also considered. Here, we develop and show a specific optimization algorithm (exercise) using LMTD and simple (optimal) design theory to establish a reference case for the Printed Circuit Heat Exchanger (PCHE). Computational Fluid Dynamics (CFD) was further used as a design tool to investigate the optimal design of PCHE thermohydraulic flow. The CFD results were validated against the Blasius correlation before being subjected to optimal design analyses. Benchmark results for the pipe flow indicated that the predictive ability of SST k-ω is superior to the other (standard and RNG k-ε and RSM) turbulence models. The difference between CFD and the empirical expression is less than 10%. (author)
SAPO-34 coated adsorbent heat exchanger for adsorption chillers
International Nuclear Information System (INIS)
In this work, adsorbent coatings on aluminum surfaces were prepared by dip-coating method starting from a water suspension of SAPO-34 zeolite and a silane-based binder. Silane-zeolite coatings morphology and surface coverage grade were evaluated by scanning electron microscopy. Adhesive and mechanical properties were evaluated by peel, pull-off, impact and micro-hardness tests, confirming the good interaction between metal substrate, binder and zeolite. Adsorption equilibrium and kinetics of water vapour adsorption on the adsorbent coating were studied in the range T = 30–150 °C and pH2O = 11 mbar using a CAHN 2000 thermo-balance. It was found that, in the investigated conditions, the organic binder doesn't affect the water adsorption capacity and adsorption kinetics of the original SAPO-34 zeolite. Subsequently, the zeolite coating was applied on a finned flat-tubes aluminum heat exchanger realizing a full-scale AdHEx with an uniform adsorbent coating 0.1 mm thick and a metal/adsorbent mass ratio = 6. The cooling capacity of the realized coated AdHEx was measured by a lab-scale adsorption chiller under realistic operating conditions for air conditioning applications. The coated AdHEx produced up to 675 W/kgads specific cooling power with a cycle time of 5 min. Adsorption stability of the coated adsorber subjected to 600 sorption cycles was successfully verified. - Highlights: • Adsorbent coatings on aluminum surfaces were prepared by dip-coating method. • Silane-zeolite coatings morphology, and mechanical properties were studied. • The zeolite coating was applied on a finned flat-tubes aluminum heat exchanger. • The coated AdHEx was tested in a lab scale adsorption chiller