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Simulation and experiment on the thermal performance of U-vertical ground coupled heat exchanger
Microsoft Academic Search
This paper presented both the numerical simulations and experiments on the thermal performance of U-vertical ground coupled heat exchanger (UGCHE). The variation of the ground temperature and heat balance of the system were analyzed and compared in different operation modes in the numerical simulation. Experiments on the operation performance of the ground-coupled heat pump (GCHP) with the UGCHE were carried
Xinguo Li; Zhihao Chen; Jun Zhao
Cooperative heat transfer and ground coupled storage system
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Metz, Philip D. (Rocky Point, NY)
A refined computer program for the transient simulation of ground coupled heat pump systems
NASA Astrophysics Data System (ADS)
The use of the earth as a heat source/sink or storage medium for various heat pump based space conditioning systems were investigated. A computer program ground coupled system (GROCS) was developed to model the behavior of ground coupling devices. The GROCS was integrated with TRNSYS, the solar system simulation program, to permit the simulation of complete ground coupled heat pump systems. Experimental results were compared to GROCS simulation results for model validation. It is found that the model has considerable validity. A refined version of the GROCS-TRNSYS program developed to model vertical or horizontal earth coil systems, which considers system cycling is described. The design of the program and its interaction with TRNSYS are discussed.
Andrews, J. W.; Metz, P. D.; Saunders, J. H.
Model for Ground-Coupled Heat and Moisture Transfer from Buildings
SciTech Connect
An important factor in soil heat transfer that is often over looked is the effect of moisture, which can vary the effective thermal conductivity by a factor of ten. The objective of this research was to investigate the ground-coupled heat and moisture transfer from buildings, and to develop results and tools to improve energy simulation of ground-coupled heat transfer.
Deru, M.
Whole-Building Energy Simulation with a Three-Dimensional Ground-Coupled Heat Transfer Model.
National Technical Information Service (NTIS)
A three-dimensional, finite-element, heat-transfer computer program was developed to study ground-coupled heat transfer from buildings. It was used in conjunction with the SUNREL whole-building energy simulation program to analyze ground-coupled heat tran...
M. Deru R. Judkoff J. Neymark
Ground coupled solar heat pump research program in the United States
The ground coupling research program funded by the Systems Development Division of the Office of Solar Applications of the US Department of Energy studies the use of the earth as a heat source/sink or storage element for solar heat pump space conditioning systems. The goal of this research program is to determine the feasibility of ground coupling, and if feasibility is confirmed, to create handbooks which facilitate widespread application of ground coupling. The research program is outlined and the research projects currently in progress and how they fit into the program are described. Progress toward the program goal is evaluated.
Metz, P D
Ground-Coupled Heating-Cooling Systems in Urban Areas: How Sustainable Are They?
ERIC Educational Resources Information Center
Ground-coupled heating-cooling systems (GCHCSs) exchange heat between the built environment and the subsurface using pipework buried in trenches or boreholes. If heat pumps in GCHCSs are powered by "green electricity," they offer genuine carbon-free heating-cooling; for this reason, there has been a surge in the technology in recent years.�
Younger, Paul L.
Analysis and field evaluation of an advanced ground-coupled heat pump system.
This paper addresses the performance of a ground-coupled heat pump (GCHP) system with a water-source heat pump (WSHP) package designed expressly for such systems for a northern climate. The research objective was to minimize the life-cycle cost (LCC) of a...
V. D. Baxter M. A. Catan H. M. Hughes P. J. Hughes R. A. O'Neil
A new approach to compute heat transfer of ground-coupled envelope in building thermal simulation software
This study presents a new approach to compute the heat transfer of ground-coupled envelope quickly and correctly which is suitable for implementation into building thermal simulation software. The heat transfer process is decomposed into three processes which are controlled by ground-coupled envelope surface temperature, outdoor ground surface temperature and the temperature difference of ground-coupled envelope surfaces. The three processes are
Xiaona Xie; Yi Jiang; Jianjun Xia
Experimental analysis of direct-expansion ground-coupled heat pump systems
Direct-expansion ground-coil-coupled (DXGC) heat pump systems have certain energy efficiency advantages over conventional ground-coupled heat pump (GCHP) systems. Principal among these advantages are that the secondary heat transfer fluid heat exchanger and circulating pump are eliminated. While the DXGC concept can produce higher efficiencies, it also produces more system design and environmental problems (e.g., compressor starting, oil return, possible ground pollution, and more refrigerant charging). Furthermore, general design guidelines for DXGC systems are not well documented. A two-pronged approach was adopted for this study: (1) a literature survey, and (2) a laboratory study of a DXGC heat pump system with R-22 as the refrigerant, for both heating and cooling mode tests done in parallel and series tube connections. The results of each task are described in this paper. A set of general design guidelines was derived from the test results and is also presented. 12 refs., 11 figs., 1 tab.
Mei, V.C.; Baxter, V.D.
Direct-expansion ground-coil-coupled (DXGC) heat pump systems have certain energy efficiency advantages over conventional ground-coupled heat pump (GCHP) systems. Principal among these advantages are that the secondary heat transfer fluid heat exchanger and circulating pump are eliminated. While the DXGC concept can produce higher efficiencies, it also produces more system design and environmental problems (e.g., compressor starting, oil return, possible ground pollution, and more refrigerant charging). Furthermore, general design guidelines for DXGC systems are not well documented. A two-pronged approach was adopted for this study: (1) a literature survey, and (2) a laboratory study of a DXGC heat pump system with R-22 as the refrigerant, for both heating and cooling mode tests done in parallel and series tube connections. The results of each task are described in this paper. A set of general design guidelines was derived from the test results and is also presented.
Mei, V. C.; Baxter, V. D.
Ground-coupled heat pump research at the University of Tennessee Washington, D.C., 10 Dec. 1984
The seasonal performance of a horizontal-coil ground-coupled heat pump system in both the heating and cooling mode was evaluated to determine its potential for use in the Knoxville, TN area. The effects of the significant parameters on performance were determined with the required data to develop an optimized system. The ground-coupled heat pump system was installed in TECH House I. The following conclusions are presented: (1) the data indicate that the ground coil heat exchanger is undersized for summer operation, operation during the winter season was acceptable with an overall seasonal performance factor of 2.6 which is higher than a typical air-air heat pump; (2) an undersized ground coil in a ground-coupled heat pump system will produce a significant performance penalty; (3) backfilling with clay must be carefully done to avoid having air pockets in the ground due to the tendency of clay to agglomerate; (4) backfilling with sand around the ground coil produced improved performance of the system during the initial summer of operation; (5) during winter operation, no electric resistance backup heating is required; (6) a ground-coupled heat pump in this area of the country must be sized based on the cooling peak which will normally result in an overdesign for the winter season, such as overdesign maybe, desirable because of reduced need for backup resistance heat.
Johnson, W. S.; McGraw, B. A.; Baugh, R. N.; Griffith, W. A.
Vertical eddy heat fluxes from model simulations
NASA Technical Reports Server (NTRS)
Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.
Stone, Peter H.; Yao, Mao-Sung
Characteristics Of Vertical Mantle Heat Exchangers For Solar Water Heaters
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 exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface.
L. J. Shah; G. L. Morrison; M. Behnia
Vertical Eddy Flux of Heat in the Atmosphere
The thermodynamics of open systems is developed for a special atmospheric system in order to obtain a precise definition of the vertical eddy flux of heat. The upward eddy flux of heat per unit area is Vzh, where is density, Vz is a specially defined fluctuation of the vertical component of velocity, and h is specific enthalpy.In terms of the
R. B. Montgomery
A cost effective vertical air\\/water solar heating collector
A description is presented of a vertical air\\/water collector which combines high efficiency with low cost. The low-cost characteristics of the total system are obtained by utilizing an air system for heat collection along with a water system for heat storage. The heat exchanger is in the top of the collector. It is protected from freezing, and is available to
T. H. Markowitz; R. L. Hummel
Calculation of vertical temperature gradients in heated rooms.
This paper deals with a simple model which predicts the vertical temperature gradient in a heated room. The gradient is calculated from a dimensionless temperature profile which is determined by two room air temperatures only, the mean temperature in the ...
H. Overby M. Steen-Thoede
The vertical structure of ocean heat transport
One of the most important contributions the ocean makes to Earth's climate is through its poleward heat transport: about 1.5 PW or more than 30% of that accomplished by the ocean-atmosphere system (Trenberth and Caron, 2001). Recently, concern has arisen over whether global warming could affect this heat transport (Watson et al., 2001), for example, reducing high latitude convection and triggering a collapse of the deep overturning circulation (Rahmstorf, 1995). While the consequences of abrupt changes in oceanic circulation should be of concern, we argue that the attention devoted to deep circulations is disproportionate to their role in heat transport. For this purpose, we introduce a heat function which identifies the contribution to the heat transport by different components of the oceanic circulation. A new view of the ocean emerges in which a shallow surface intensified circulation dominates the poleward heat transport.
Boccaletti, G.; Ferrari, R.; Adcroft, A.; Ferreira, D.; Marshall, J.
New solutions for the short-time analysis of geothermal vertical boreholes
Many models, either numerical or analytical, have been proposed to analyse the thermal response of vertical heat exchangers that are used in ground coupled heat pump systems (GCHP). In both approaches, most of the models are valid after few hours of operation since they neglect the heat capacity of the borehole. This is valid for design purposes, where the time
Louis Lamarche; Benoit Beauchamp
Supercritical-water heat transfer in a vertical bare tube
This paper presents selected results on heat transfer to supercritical water flowing upward in a 4-m-long vertical bare tube. Supercritical-water heat-transfer data were obtained at pressures of about 24MPa, mass fluxes of 200�1500kg\\/m2s, heat fluxes up to 884kW\\/m2 and inlet temperatures from 320 to 350�C for several combinations of wall and bulk-fluid temperatures that were below, at or above the
Sarah Mokry; Igor Pioro; Pavel Kirillov; Yevgeniy Gospodinov
Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels
Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)
Pastuszko, Robert [Chair of Thermodynamics and Fluids Mechanics, The Kielce University of Technology, Al. Tysiaclecia P.P. 7, 25-314 Kielce (Poland)
Pr<1 intrusion flow induced by a vertical heated wall.
A horizontal flow induced by a vertical heated wall with a low Prandtl number (e.g., Pr<1 for air and liquid metals) is common in nature and industry. In this paper, a Pr<1 intrusion flow induced by a vertical heated boundary of an open sided cavity (that is, a cavity with one heated wall and open at the other end) is investigated by a scaling analysis and direct numerical simulations. The scaling analysis of the intrusion flow reveals that there are four possible flow regimes dependent on the Rayleigh and Prandtl numbers. In a typical case, the intrusion flow could travel under different dynamical and thermal processes such as unsteady (or steady) conduction-viscous, conduction-inertial, and convection-inertial dominance. Proper scaling relations have been presented to quantify these flows under different flow regimes. Furthermore, corresponding numerical simulations have verified the scaling results. PMID:20866916
Xu, Feng; Patterson, John C; Lei, Chengwang
Bound on vertical heat transport at large Prandtl number
We prove a new upper bound on the vertical heat transport in Rayleigh-B�nard convection of the form c Ra( under the assumption that the ratio of Prandtl number over Rayleigh number satisfies {Pr}/{Ra}?c0 where the non-dimensional constant c0 depends on the aspect ratio of the domain only. This new rigorous bound agrees with the (optimal) Ra bound (modulo logarithmic correction) on vertical heat transport for the infinite Prandtl number model for convection due to Constantin and Doering [P. Constantin, C.R. Doering, Infinite Prandtl number convection, J. Stat. Phys. 94 (1) (1999) 159-172] and Doering, Otto and Reznikoff [C.R. Doering, F. Otto, M.G. Reznikoff, Bounds on vertical heat transport for infinite Prandtl number Rayleigh-B�nard convection, J. Fluid Mech. 560 (2006) 229-241]. It also improves a uniform (in Prandtl number) Ra bound for the Nusselt number [P. Constantin, C.R. Doering, Heat transfer in convective turbulence, Nonlinearity 9 (1996) 1049-1060] in the case of large Prandtl number.
Wang, Xiaoming
Retrieving Latent Heat Vertical Structure Using Precipitation and Cloud Profiles
The latent heat (LH) released from tropical precipitation plays a critical role in driving regional and global atmosphere circulation. However, the vertical distribution of LH is one of most difficult parameters to be measured and has a large uncertainty in both residual diagnostic products and satellite retrievals. Most of current satellite LH products use limited observational information of precipitation and cloud profiles and highly depend on cloud resolving model (CRM) simulations. Our novel approach, distinguishing from existing schemes, is directly using observable precipitation and cloud profiles in combination with phase change partition parameterization of various kinds from the CRM simulations to produce the latent heating profiles. This hybrid latent heat algorithm separately deals with the condensation-evaporation heating (LHc_e), the deposition-sublimation heating (LHd_s) and the freezing-melting heating (LHf_m) for convective rain, stratiform rain, and shallow warm rain. Each component is based on physical processes, such as nucleation and auto conversion, by combining observable precipitation and cloud profiles. Although the proposed algorithm utilizes microphysical parameterizations from a specific CRM, the general LH vertical structure is primarily determined by the precipitation and cloud profiles observable from cloud and precipitation radars available at ground sites or from satellite platforms, and less sensitive to the specific CRM. The self consistency tests of this algorithm show good agreements with the CRM simulated LH at different spatial and temporal scales, even at simultaneous and pixel level. The applications of this algorithm are expected to provide new information for understanding the heating budget in the atmosphere and its impacts on the atmosphere circulations at various spatial and temporal scales.
Li, R.; Min, Q.; Wu, X.
Mixed Convective Boiling Heat Transfer in a Vertical Capillary Structure Heated Asymmetrically
Mixed convective boiling heat transfer in a vertically oriented capillary porous structure with asymmetric heating of opposing walls is numerically investigated using a multiphase mixture model. Liquid saturation distributions, isotherms, as well as liquid and vapor velocity fields subjected to both superimposed aiding and opposing flows are analyzed and presented. The liquid velocity distributions for both aiding and opposing flows
T. S. Zhao; Q. Liao
Flow regimes and heat transfer in vertical narrow annuli
In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ``isolated`` bubbles, ``coalesced`` bubbles and liquid deficient regions have been defined.
Ulke, A.; Goldberg, I.
Spray cooling heat-transfer with subcooled trichlorotrifluoroethane (Freon-113) for vertical constant heat flux surfaces
Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.
Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering
Vertical Variation In Heat Flow Density: Palaeoclimate After All?
Vertical variation in heat flow density (HFD) in the upper crust is one of the Sbig' � problems in geothermics. Several factors have been proposed to produce the variation, such as convective heat transfer by migration of fluids, palaeoclimatic conductive dis- turbances, endo/exothermic mineral reactions, or thermal conductivity contrasts. We present evidence indicating that palaeoclimatic surface temperature variations are the major factor behind the vertical variation in stable continental areas. We report an analysis of heat flow density (HFD) in the Fennoscandian Shield (FS) and East Euro- pean Platform (EEP) where HFD shows a systematic variation with depth. The HFD data (1352 values) averaged in 25 m depth intervals and in 1 degree times 2 degrees latitude-longitude areas increase from about 35-40 mW m-2 in the first 500 m to about 45 mW m-2 at 1000 m, reaching finally about 50 mW m-2 between 1000-3000 m and deeper. We attribute this variation to long-term climatic changes in ground sur- face temperatures (GST) during the Weichselian (Late Pleistocene) glaciation and the Holocene. Monte Carlo inversion was applied for determining ground surface temper- ature histories during the past 100,000 years, and the results indicate a gradual cool- ing through the Weichselian until the Last Glacial Maximum, followed by an average warming of 8.0 s� 4.5 degrees at about 10,000 years BP.
Kukkonen, I. T.; Joeleht, A.
Effect of pressure on critical heat flux in uniformly heated vertical annulus under low flow conditions
Critical heat flux (CHF) experiments have been carried out in a wide range of pressure for an internally heated vertical annulus. The experimental conditions covered a range of pressure from 0.57 to 15.01 MPa, mass fluxes of 0 kg m?2 s?1 and from 200 to 650 kg m?2 s?1, and inlet subcoolings from 85 to 413 kJ kg?1. Most of
Se-Young Chun; Heung-June Chung; Sang-Ki Moon; Sun-Kyu Yang; Moon-Ki Chung; Thomas Schoesse; Masanori Aritomi
Application of Ground-Coupled GPR to Pavement Evaluation.
Four case studies are presented in which ground-coupled ground-penetrating radar (GPR) was used successfully to identify subsurface problems in highway projects. These include identifying the extent of a subsurface aquifer so that a drainage system can be...
T. Scullion S. Servos J. Ragsdale T. Saarenketo
Conveccion de calor en conjuntos de cilindros. (Heat convection in a set of three vertical cylinders).
Experimental results on temperature and heat flow in a set of three vertical cylinders with internal generation of heat, water submerged and in free convection are presented in this work . Temperature distribution, Nusselt number and convective coefficien...
M. L. Serrano Ramirez
CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure
The CFD analysis of heat transfer within a bottom heated vertical concentric cylindrical enclosure is important with respect to the process in the chemical and process industries. The research work focuses on the CFD analysis of the enclosure with respect to the machines used for the segregation of chemicals in the chemical industries. The CFD simulations are performed to study the effects of inner cylinder material and outer cylinder geometric configurations on the heat transfer mechanism in the enclosure. The CFD simulations are conducted at a bottom disc temperature of 393 K and compared with the published results at a temperature of 433 K. This research study depicts the behavior of bottom heated vertical concentric cylindrical enclosure at different bottom disc temperatures. This study also investigates the heat transfer mechanism of the enclosure using different inner cylinder materials and different configurations of the outer cylinder. In such enclosures a uniform temperature is required for the segregation of chemicals. A more uniform temperature is observed in the enclosure by using aluminum inner cylinder of the bottom disc and using two different diameter outer cylinders as compared to the mild steel and stainless steel.
Hussain Malik, Asif; Shah, Ajmal; Khushnood, Shahab
Natural convection heat transfer from vertical parallel plates to air
Two-dimensional Navier-Stokes and energy equations are numerically solved for laminar natural convection of air between vertical parallel plane plates with uniform heat flux. Calculations are carried out under the conditions of the modified Grashof number (2.3 x 10(exp 3) less than or equals to Gr(sup *) less than or equals to 8.8 x 10(exp 5)) and height to plate spacing ratio (8 less than or equals to l/h less than or equals to 30), which covers the practical range encountered with the air cooling system of electronic equipment. The numerical solutions are compared with present experimental results. The local Nusselt numbers and induced flow rates obtained numerically agree well with those measured. A correlation expression for the local Nusselt number is proposed which can predict the local plate temperature within 5 percent error. When the value of dimensionless variable Phi = ((h/x)Gr(sup *)Pr)/((h/l)Gr(sup *)Pr) is greater than approximately 10(exp 2). The existing results based on the boundary layer approximation are found to be not applicable for predicting the maximum plate temperature.
Fujii, Motoo; Gima, Satoru; Tomimura, Toshio; Zhang, Xing
Diffusive vertical heat flux in the Canada Basin of the Arctic Ocean inferred from moored instruments
Observational studies have shown that an unprecedented warm anomaly has recently affected the temperature of the Atlantic Water (AW) layer lying at intermediate depth in the Arctic Ocean. Using observations from four profiling moorings, deployed in the interior of the Canada Basin between 2003 and 2011, the upward diffusive vertical heat flux from this layer is quantified. Vertical diffusivity is first estimated from a fine-scale parameterization method based on CTD and velocity profiles. Resulting diffusive vertical heat fluxes from the AW are in the range 0.1-0.2 W m-2 on average. Although large over the period considered, the variations of the AW temperature maximum yields small variations for the temperature gradient and thus the vertical diffusive heat flux. In most areas, variations in upward diffusive vertical heat flux from the AW have only a limited effect on temperature variations of the overlying layer. However, the presence of eddies might be an effective mechanism to enhance vertical heat transfer, although the small number of eddies sampled by the moorings suggest that this mechanism remains limited and intermittent in space and time. Finally, our results suggest that computing diffusive vertical heat flux with a constant vertical diffusivity of �2 � 10-6 m2 s-1 provides a reasonable estimate of the upward diffusive heat transfer from the AW layer, although this approximation breaks down in the presence of eddies.
Lique, Camille; Guthrie, John D.; Steele, Michael; Proshutinsky, Andrey; Morison, James H.; Krishfield, Richard
Effects of Convective Heating on Movement and Vertical Coupling of Tropical Cyclones: A Numerical Study*.
The influence of convective heating on movement and vertical coupling of tropical cyclones (TCs) is investigated using a hurricane model with different environmental flows. The authors identify two processes by which convective heating may affect TC motion. One is the advection of symmetric potential vorticity (PV) by heating-induced asymmetric flow. The other is the direct generation of a positive PV tendency by asymmetric heating, which acts to shift a TC to the region of maximum downward gradient of asymmetric heating. A steering level exists that is located at the level where the direct influence of asymmetric heating vanishes, normally in the lower troposphere. At that level, a TC moves with the asymmetric flow averaged within a radius of 200 km, because the influence of asymmetric flows on TC motion is weighted by the horizontal PV gradient that is primarily confined within the TC core. Although the vertical shear in the asymmetric flow (including environmental and heating-induced flows) could tilt the vortex, the influence of asymmetric heating tends to offset the vertical tilt caused by the vertical shear through a fast adjustment between the asymmetric wind and diabatic heating. Therefore, diabatic heating enhances the vertical coupling.
Wu, Liguang; Wang, Bin
Critical heat flux prediction for saturated flow boiling of water in vertical tubes
This study presents a new analytical model for the prediction of the critical heat flux (CHF) in water saturated flow boiling in round vertical and uniformly heated pipes. The CHF is assumed to occur in annular flow when the liquid film vanishes at the exit section of the heated channel. Channel pressure drop is calculated using the Friedel correlation. Liquid
Gian Piero Celata; Kaichiro Mishima; Giuseppe Zummo
Investigation of natural-convection heat transfer coefficient on a vertical square fin of finned-tube heat exchangers
The finite difference method in conjunction with the least-squares scheme and the experimental temperature data is proposed to predict the average natural-convection heat transfer coefficient and the fin efficiency on a vertical square fin of one-circular tube plate finned-tube heat exchangers. In the present study, the radiation and convection heat transfer coefficients are simultaneously taken into consideration. The heat transfer
Han-Taw Chen; Jui-Che Chou
An experimental investigation of heat transfer coefficients has been carried out in mechanically agitated air-water dispersions to and from vertical tubes acting as baffles in addition to heat exchange surface in a vertical cylindrical tank. Air was dispersed into water, which served as a two-phase fluid. Agitation was provided by a dual, 4-blade turbine impeller. A modified Reynolds number has
An analytical model for near-saturated pool boiling critical heat flux on vertical surfaces
Photographic studies of vertical pool boiling for near-saturated conditions were conducted in order to determine the critical heat flux (CHF) trigger mechanism. The studies revealed that, for heat fluxes near CHF, vertical pool boiling exhibits vapor behavior similar to that observed in flow boiling. At fluxes slightly below CHF, the Kelvin-Helmholtz instability creates a wavy layer at the liquid-vapor interface.
Issaim Mudawar; Alicia H. Howard; Christopher O. Gersey
Power-law fluid flow in heated vertical ducts
A hydrodynamically and thermally fully developed flow in a vertical duct is investigated. It is assumed that the wall of the duct is maintained at a temperature which varies linearly with respect to the depth of the duct to model a vertical duct in the Earth. Furthermore, in order to investigate flows during the drilling of muds and the cementing process in oil wells, the fluid is assumed to be a power-law fluid and the fluid flow in concentric annuli are investigated. The conditions under which multiple solutions are obtained is studied and the effects of the Rayleigh number n, the relative thickness of the channels, and the enforced pressure gradient are investigated.
Jones, A. T.; Ingham, D. B.
Method and apparatus for determining vertical heat flux of geothermal field
A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.
Poppendiek, Heinz F. (LaJolla, CA)
Convective heat and mass transfer in water at super-critical pressures under heating or cooling conditions in vertical tubes
Forced and mixed convection heat and mass transfer are studied numerically for water containing metallic corrosion products\\u000a in a heated or cooled vertical tube with variable thermophysical properties at super-critical pressures. The fouling mechanisms\\u000a and fouling models are presented. The influence of variable properties at super-critical pressures on forced or mixed convection\\u000a has been analyzed. The differences between heat and
Pei-Xue Jiang; Ze-Pei Ren; Bu-Xuan Wang
Critical heat flux during natural convective boiling on uniformly heated inner tubes in vertical annular tubes submerged in saturated liquid
An experimental study has been made of critical heat flux (CHF) of natural convective boiling on uniformly heated inner tubes in vertical annular tubes. The experiment was performed at a pressure ofP=0.1 to 3.1 MPa for the clearance of 0.4 to 4.0 mm, the heated tube diameter of 5 to 10.6 mm, the annular tube length ofL=58 to 840 mm
Masanori Monde; Yuichiro Mitutake; Shinji Kubo
Natural convection heat transfer from a vertical plate to supercritical helium
A vertical copper plate was used to study heat transfer by natural convection to helium at supercritical pressures. The results revealed an appreciable discrepancy between the experimental data for the mean heat transfer coefficient and the value of this coefficient, calculated from the equation for carbon dioxide and water at super-critical pressures. A modified equation, written in dimensionless numbers, which
V. I. Deev; A. K. Kondratenko; V. I. Petrovichev; V. E. Keilin; I. A. Kovalev
Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side
In the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.
Bieli?ski, Henryk; Mikielewicz, Jaros?aw
Heat flow experiment. [direct measurement of vertical flow of heat through lunar soil in Apollo 17 lunar landing site area
The heat flow experiment conducted during the Apollo 17 flight in the Taurus-Littrow area of the moon is discussed. The concept of the experiment is based on the direct measurement of the vertical flow of heat through the regolith. The measurement is made far enough below the surface so that the time-varying heat flow resulting from the very large diurnal variations of the surface temperature is small as compared with the flow from the interior. The equipment used for the experiment is described and illustrated. Graphs are developed to present the results of heat flow and surface temperature measurements.
Langseth, M. G., Jr.; Keihm, S. J.; Chute, J. L., Jr.
Natural convection along slender vertical cylinders with variable surface heat flux
Heat transfer by natural convection along a vertical cylinder has been analyzed rather extensively by many investigators using different solution methods. The major restriction to most of these studies is that the solutions are valid only for cylinders with small surface curvature, that is, for cylinders whose diameters are not small. To data no analysis seems to have been presented for natural convection along slender vertical cylinders under the variable surface heat flux condition, and this has motivated the present study as a supplement to the solution of the problem with variable wall temperature.
Heckel, J.J.; Chen, T.S.; Armaly, B.F. (Univ. of Missouri, Rolla (United States))
Experimental study of natural convective heat transfer in a vertical hexagonal sub channel
The development of new practices in nuclear reactor safety aspects and optimization of recent nuclear reactors, including the APWR and the PHWR reactors, needs a knowledge on natural convective heat transfer within sub-channels formed among several nuclear fuel rods or heat exchanger tubes. Unfortunately, the currently available empirical correlation equations for such heat transfer modes are limited and researches on convective heat transfer within a bundle of vertical cylinders (especially within the natural convection modes) are scarcely done. Although boundary layers around the heat exchanger cylinders or fuel rods may be dominated by their entry regions, most of available convection correlation equations are for fully developed boundary layers. Recently, an experimental study on natural convective heat transfer in a subchannel formed by several heated parallel cylinders that arranged in a hexagonal configuration has been being done. The study seeks for a new convection correlation for the natural convective heat transfer in the sub-channel formed among the hexagonal vertical cylinders. A new convective heat transfer correlation equation has been obtained from the study and compared to several similar equations in literatures.
Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur [Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Technology Center for Materials and Radiometry, National Nuclear Energy Agency, Bandung (Indonesia); Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132 (Indonesia); Nuclear Energy Regulation Agency, Jakarta (Indonesia)
Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur
Study on falling film generation heat transfer of lithium bromide solution in vertical tubes
Falling film generation process in lithium bromide absorption refrigeration generation system is researched in this paper.\\u000a To describe the coupled heat and mass transfer of laminar falling film in vertical generation tube, a mathematical model is\\u000a developed, in which the effect of mass transfer on heat transfer is carefully evaluated. Moreover, an equation related Re\\u000a number with solution volume flow
Chengming Shi; Canjun Xu; Huili Hu; Yang Ying
Developing Flow of Mixed Convection in a Vertical Rectangular Duct with One Heating Wall
Heat transfer and flow patterns of laminar mixed confection in the developing region of a vertical rectangular duct with one heating wall have been investigated numerically in this study. The parabolic boundary layer model is adopted to predict the three-dimensional buoyancy-assisted flow field. Governing equations art solved by using the SIMPI.KC method coupled with a forward marching, implicit finite difference
Chin-Hsiang Cheng; Chun-Jen Weng
Laminar natural convection heat and mass transfer in vertical rectangular ducts
The present work investigates numerically the laminar natural convection heat and mass transfer in open vertical rectangular ducts with uniform wall temperature\\/uniform wall concentration (UWT\\/UWC) or uniform heat flux\\/uniform mass flux (UHF\\/UMF) boundary conditions. The vorticity�velocity formulation is applied to solve for the coupled momentum, energy and concentration equations. Results of dimensionless induced volume rate Q, average Nusselt number Nu
Kuan-Tzong Lee
Heat transfer enhancement by the chimney effect in a vertical isoflux channel
The ease of thermal control by means of air natural convection stimulates the investigation of configurations with the aim at improving the thermal performance. The effect of adding adiabatic extensions downstream of a vertical isoflux symmetrically heated channel has been experimentally analyzed. Optimal configurations have been identified through the measured wall temperature profiles, with reference to the extension and expansion
A Auletta; O Manca; B Morrone; V Naso
Local Heat Transfer During Condensation with Forced Convection in a Vertical Tube.
The local heat transfer coefficients during the condensation of pure substances in a vertical tube has been measured by varying separately the mass flux density of the vapor and the trickling quantity. The substances used in the experiments are water and ...
F. Blangetti
Three-dimensional computation of heat transfer from flames between vertical parallel walls
The heat transfer from turbulent diffusion flames between vertical walls has been computed for different wall and burner configurations. The buoyancy-modified k ? ? model was used to study the turbulent characteristics of the flow. The flamelet concept, coupled to a prescribed probability density function, was employed to model the nonpremixed combustion process. With the nucleation, surface growth, coagulation, and
Zhenghua Yan; G�ran Holmstedt
Non-linear dynamics and pattern formation in a vertical fluid layer heated from the side
We study both experimentally and numerically the convective flow in a tall vertical slot with differently heated walls. The flow is investigated for the fluid with the Prandtl number Pr=26, which is large enough to ensure the traveling waves as primary instability and small enough to prevent boundary layer convection. The flow evolution is determined on the base of the
Dmitry A Bratsun; Alexej V Zyuzgin; Gennady F Putin
Comparison of two vertical condensation obturation techniques: Touch 'n Heat modified and System B
Abstract Silver GK, Love RM and Purton DG. Comparison of two vertical condensation,obturation,techniques:,Touch,�n Heat modified and System B. International Endodontic Journal, 32, 287?295, 1999. Aim,The aims,of this study were,firstly to compare
G. K. Silver; R. M. Love; D. G. Purton
Empirical Models of the Eddy Heat Flux and Vertical Shear on Short Time Scales
The relationship between the eddy heat flux and vertical shear in the extratropical atmosphere is studied by developing various linear stochastic models fitted to the observed January and July Northern Hemispheric data. Models are univariate or bivariate, continuous or discrete. An objective procedure selects the second-order bivariate model as most appropriate in midlatitudes. The first-order continuous bivariate model indicates that
Steven J. Ghan
Prediction of the critical heat flux in annular regime in various vertical channels
The axial variation of film flow rate in annular regime was analyzed to predict the critical heat flux in water saturated flow boiling in various vertical channels. In the analyses, several quantities including the deposition and entrainment rates of droplets were evaluated with the correlations that were based on the separate experimental data of film flow rate and droplet flow
Tomio Okawa; Akio Kotani; Isao Kataoka; Masanori Naitoh
Experimental study of thermally induced oscillations and heat transfer in an ascending flow of supercritical helium in a vertical tube
An experimental study of the conditions for the onset of thermally induced oscillations and their influence on heat transfer in an ascending flow of supercritical helium in a heated vertical tube is reported.
V. A. Bogachev; V. M. Eroshenko; E. V. Kuznetsov
Buoyancy effects on the laminar boundary layer heat transfer along vertically moving cylinders
The local similarity method (Lloyd, Sparrow, 1970) is used to study the effects of buoyancy force on the laminar boundary layer heat transfer along vertically moving cylinders. Cases of prescribed surface temperature and wall heat flux in power of streamwise distance are analyzed. Local similarity solutions are obtained to show the effects of the transverse curvature of the cylinder surface and buoyancy parameters on the surface friction and heat transfer rate. It is known, however, that the local non-similarity method (Sparrow, Quack, Boerner, 1970) and the finite difference method (Mucoglu, Chen, 1979) would give more accurate results.
Lin, H.-T.; Shih, Y.-P.
Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation
In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.
Brandon, S.; Derby, J. J.
Mixed Convection Heat Transfer in Micropolar Nanofluid over a Vertical Slender Cylinder
Analysis is carried for the problem of boundary layer steady flow and heat transfer of a micropolar fluid containing nanoparticles over a vertical cylinder. The governing partial differential equations of linear momentum, angular momentum, heat transfer and nano concentration are reduced to nonlinear coupled ordinary differential equations by applying the boundary layer approximations and a suitable similarity transformation. These nonlinear coupled ordinary differential equations, subject to the appropriate boundary conditions, are then solved by using the homotopy analysis method. The effects of the physical parameters on the flow, heat transfer and nanoparticle concentration characteristics of the model are presented through graphs and the salient features are discussed.
Abdul, Rehman; Nadeem, S.
Prediction of two-phase flow and heat transfer in vertical pipes
A prediction procedure for gas-solid flows in vertical pipes with and without heat transfer is presented. Separate conservation equations are formulated for each phase and the interaction between the phases is accounted for by including interfacial drag and energy exchange terms in the corresponding equations. A 'two-phase two-equation model' of turbulence is used. The logarithmic wall function for single phase is modified for two-phase flow, in order to account for heat and momentum transfer to each phase at the wall. Good agreement is obtained between predictions and experimental data for flow and heat transfer in vertical pipes for particle sizes 30,100 and 800 microns.
Abou-Ellail, M. M. M.; Abou-Arab, T. W.
Experimental research on heat transfer of natural convection in vertical rectangular channels with large aspect ratio
This work presents the experimental research on the steady laminar natural convection heat transfer of air in three vertical thin rectangular channels with different gap clearance. The much higher ratio of width to gap clearance (60-24) and the ratio of length to gap clearance (800-320) make the rectangular channels similar with the coolant flow passage in plate type fuel reactors. The vertical rectangular channels were composed of two stainless steal plates and were heated by electrical heating rods. The wall temperatures were detected with the K-type thermocouples which were inserted into the blind holes drilled in the steal plates. Also the air temperatures at the inlet and outlet of the channel were detected. The wall heat fluxes added to the air flow were calculated by the Fourier heat conduction law. The heat transfer characteristics were analyzed, and the average Nusselt numbers in all the three channels could be well correlated with the Rayleigh number or the modified Rayleigh number in a uniform correlation. Furthermore, the maximum wall temperatures were investigated, which is a key parameter for the fuel's integrity during some accidents. It was found that even the wall heat flux was up to 1500 W/m{sup 2}, the maximum wall temperature was lower than 350 C. All this work is valuable for the plate type reactor's design and safety analysis. (author)
Lu, Qing; Qiu, Suizheng; Su, Guanghui [State Key Laboratory of Multi Phase Flow in Power Engineering, Xi'an JIaotong University, Xi'an, Shaanxi 710049 (China); School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China); Tian, Wenxi; Ye, Zhonghao [School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China)
Enhancing heat transfer rates from closed-sided, open-topped heat exchangers, each having vertical rectangular fins extending upwards from a horizontal base
The almost two-dimensional steady-state rates of heat loss from arrays of uniformly-spaced vertical rectangular fins, extending upwards--in otherwise stagnant air--from horizontal heated bases, have been measured. (The vertical air gaps between the fins were closed at their sides, by insulated vertical end-barriers.) The effects of various combinations of height, thickness and spacing of the fins, for different base temperatures (in
K. Jambunathan; S. D. Probert; M. J. Shilston
Experimental investigation of the local heat transfer in a vertical gas-liquid slug unit
Heat transfer mechanism in two-phase flows and particularly in vertical slug flow is of high interest both for basic hydrodynamic research and for industrial applications. Two-phase slug flow is highly complicated and only a limited number of heat transfer studies have been carried out. The flow field around a single Taylor bubble propagating in a vertical pipe can be subdivided into three distinct hydrodynamic regions: the gas bubble surrounded by a thin liquid film, a highly turbulent liquid wake in the vicinity of the bubble bottom, and the far wake region. Experimental and theoretical works were presented during the last decades investigating the hydrodynamic parameters in each region. Due to the complexity and intermittent nature of slug flow the existing data on the heat transfer in slug flow is limited to a narrow range of operational conditions. To improve the understanding of the heat transfer mechanism in slug flow a new experimental setup was constructed. A part of the vertical pipe wall was replaced by a thin metal foil heated by electrical current. An IR video camera was used to determine the temporal variation of the instantaneous temperature field along the foil at two locations: at the thermal entrance region and at the upper part of the foil where thermal boundary is thicker. The video camera was synchronized with a sensor that determined the instantaneous location of the Taylor bubble. The results of the instantaneous heat transfer measurements along the liquid film and in the wake of the Taylor bubble can be correlated with the detailed velocity measurements carried out in the same facility (Shemer et al. 2007)[1]. The effect of the local hydrodynamic parameters on the heat transfer coefficient in each region is examined.
Babin, Valery; Shemer, Lev; Barnea, Dvora
Heat transfer to water from a vertical tube bundle under natural-circulation conditions. [PWR; BWR
The natural circulation heat transfer data for longitudinal flow of water outside a vertical rod bundle are needed for developing correlations which can be used in best estimate computer codes to model thermal-hydraulic behavior of nuclear reactor cores under accident or shutdown conditions. The heat transfer coefficient between the fuel rod surface and the coolant is the key parameter required to predict the fuel temperature. Because of the absence of the required heat transfer coefficient data base under natural circulation conditions, experiments have been performed in a natural circulation loop. A seven-tube bundle having a pitch-to-diameter ratio of 1.25 was used as a test heat exchanger. A circulating flow was established in the loop, because of buoyancy differences between its two vertical legs. Steady-state and transient heat transfer measurements have been made over as wide a range of thermal conditions as possible with the system. Steady state heat transfer data were correlated in terms of relevant dimensionless parameters. Empirical correlations for the average Nusselt number, in terms of Reynolds number, Rayleigh number and the ratio of Grashof to Reynolds number are given.
Gruszczynski, M.J.; Viskanta, R.
Fundamental Study of Local Heat Transfer in Forced Convective Boiling of Ammonia on Vertical Flat Plate
In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2�s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.
Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki
General analysis of steady laminar mixed convection heat transfer on vertical slender cylinders
A general analysis has been developed to study fluid flow and heat transfer characteristics for steady laminar mixed convection on vertical slender cylinders covering the entire range from pure forced to pure natural convection. Two uniquely transformed sets of axisymmetric boundary-layer equations for the constant wall heat flux case and the isothermal surface case are solved using a two-point finite difference method with Newton linearization. Of interest are the effects of the new mixed convection parameter, the cylinder heating/cooling mode, the transverse curvature parameter, and the Prandtl number on the velocity/temeprature profiles and on the local skin friction parameter and the heat transfer parameter. The results of the validated computer simulation model are as follows. Depending upon the magnitude and direction of the buoyancy force, i.e., the value of the mixed convection parameter and the heating or cooling mode applied, natural convection can have a significant effect on the thermal flow field around vertical cylinders. Specifically, strong variations of the local skin friction parameter and reversing trends in the heat transfer parameter are produced as the buoyancy force becomes stronger in aiding flow. The skin friction parameter increases with higher curvature parameters and Prandtl numbers. Similarly, the modified Nusselt number is larger for higher transverse curvature parameters; however, this parameter may reverse the impact of the Prandtl number on the Nusselt number for predominantly forced convection.
Wang, T.Y.; Kleinstreuer, C. (North Carolina State Univ., Raleigh (United States))
Remote sensing of vertical velocity variance and surface heat flux in a convective boundary layer
The vertical velocity variance in the convective atmospheric boundary layer is estimated from measurements made with a 915-MHz boundary layer wind-profiling radar. The vertical velocity variance estimates are used to infer the surface virtual heat flux through a relationship with the convective velocity scale w{sub *}. The flux estimates are compared with in situ surface flux measurements and estimates extrapolated to the surface from direct eddy correlation measurements made with a profiler and radio acoustic sounding system. The measurements were made during the Rural Oxidants in the Southern Environment II Experiment in June 1992. The experiment area is primarily pine forest, and the dominant weather conditions were hot with light winds. The profiler variance measurements are compatible with theory and earlier observations. Both remote radar methods of estimating surface virtual heat flux agree with in situ measurements to within the sampling uncertainty. 28 ref., 6 figs.
Angevine, W.M. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States); Doviak, R.J. [National Severe Storms Lab., Norman, OK (United States)] [National Severe Storms Lab., Norman, OK (United States); Sorbjan, Z. [Univ. of Oklahoma, Norman, OK (United States)] [Univ. of Oklahoma, Norman, OK (United States)
Slide dampers for a vertical type of apparatus for continuously heat-treating solid waste
This patent describes a slide damper system used for a vertical type of furnace for continuously heat-treating non-particulate matter to recover the resulting combustive gases and\\/or liquids, comprising a gas sealing slide damper disposed in the upper portion of the furnace for sealing the interior of the furnace from the open air; at least two V-shaped slide damper means having
K. Michimae; A. Amamiya; H. Akimoto
Steady gas hydrate growth along vertical heat transfer tube without stirring
The hydration characteristics of a quiescent reactor with inner-placed vertical heat transfer tube were researched, the reaction materials were 300ppm sodium dodecyl sulfate water solution and R141b. The growth morphology were described through the photos taken during the growth\\/decomposition processes. The temperatures of two points inside the reactor were also recorded and analyzed. The mass transfer mechanism was explained by
Yingming Xie; Kaihua Guo; Deqing Liang; Shuanshi Fan; Jianming Gu
Effects of confinement and pressure on critical heat flux during natural convective boiling in vertical channels
An experimental study has been carried out for the critical heat flux (CHF) during the natural convective boiling of R-113 at various pressures in a vertical channel. The pressure ranges from 1 to 3 bar and the channel gap-size from 0.3 mm to 2.5 mm as its height is kept constant. Data for pool boiling are also obtained. At all
J. Bonjour; M. Lallemand
Nondimensional analysis of boiling dry a vertical channel with a uniform heat flux
A thermal-hydraulic model has been developed for describing the phenomenon of hydrodynamically-controlled dryout, or the boil-off phenomenon, in a vertical channel with a spatially-averaged or uniform heat flux. The use of the drift flux correlation for the void fraction profile, along with mass and energy balances for the system, leads to a dimensionless closed-form solution for the predictions of two-phase
K. H. Sun; R. B. Duffey; C. Lin
Development of an Algorithm to Predict Vertical Heat Transfer Through Ceiling\\/Floor Conduction
This paper describes a new algorithm of the Consolidated Fire Growth and Smoke Transport (CFAST) fire model and compares the results with data from real-scale fire tests conducted aboard the ex-USS Shadwell, the U.S. Navy's Research and Development Damage Control Platform. The new phenomenon modeled in this work is the conduction of heat in the vertical direction. The Shadwell tests
J. L. Bailey; W. W. Jones; P. A. Tatem; G. P. Forney
An approach to heat and mass transfer analysis during film condensation inside a vertical tube
An Investigation was conducted to determine the effects of non-condensing gas on vapor condensation. Experiments were carried out during condensation of a mixture of water vapor/non-condensing gas along the inner surface of a vertical tube. Air was used as non-condensing gas and the various profiles of the water vapor/non-condensing gas mixture were employed. A theoretical analysis to predict the heat and mass transfer is presented. The amount of the condensed water obtained by the experiments was found to be close to the theoretical results. The obtained heat and mass transfer results were in good agreement with earlier published results.
Kotcioglu, I.; Gullapoglu, S. (Ataturk Univ., Erzurum (Turkey)); Uyarel, A.Y. (Gazi Univ., Ankara (Turkey)); Kaygusuz, K. (Karadeniz Technical Univ., Trabzon (Turkey)); Dincer, I. (TUBITAK-Marmara Research Center, Kocaeli (Turkey))
Radiative-convective heat transfer to solid spherical particles in a vertical channel flow
A numerical study has been conducted pertaining to the problem of radiative convective heat transfer to solid spherical particles in a vertical channel flow. The gas phase is treated within the context of an Eulerian (continuum) formulation. For the particulate phase, a Lagrangian approach has been employed that includes two-way coupling of momentum and heat transfer between phases. The gas flow is in laminar regime and the particle Reynolds number based on the particle radius and skip velocity between phases is of order one. The particulate phase is dilute enough that direct particle, particle interactions are negligible but particle volume fraction effects are retained in the transport equations for the gas phase. The particle and channel wall surfaces are taken as diffusely emitting and reflecting. For the particulate phase, radiative heat transfer is directly coupled with convective heat transfer through the energy conservation equation and for the walls, through the thermal boundary condition.
Lee, J. S.
Augmentation of heat transfer in a bubble agitated vertical rectangular channel
This paper presents the results of an experimental study of convective heat transfer between three parallel vertical plates symmetrically spaced with and without bubble agitation to ascertain the degree of augmentation of the heat transfer coefficients due to agitation. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical rectangular channels of dimensions 20 cm � 3.5 cm � 35 cm (length W, gap L, height H) each. At the bottom of the hot and cold plates air spargers were fitted. Water/ethylene glycol (100%) was used to fill the channels. The superficial gas velocity ranged from 0.0016 to 0.01 m/s. Top, bottom and sides of the channels were open to the water/ethylene glycol in the chamber which is the novel aspect of this study. Experimental data have been correlated as under: Natural convective heat transfer: Nu = 0.60 Gr 0.29, r = 0.96, ? = 0.186, 1.17 E6 < Gr < 1.48 E7; Bubble agitated heat transfer: St = 0.11( ReFrPr 2)-0.23, r = 0.82, ? = 0.002, 1.20 E-2 < ( ReFrPr 2) < 1.36 E2.
Mitra, Asish; Dutta, Tapas Kumar; Ghosh, Dibyendu Narayan
Aerosol effect on atmospheric heating rates in the Mediterranean region using vertically resolved satellite aerosol data
It is well known that the main direct effect of aerosols is the cooling of the surface and warming of the atmosphere, which impact atmospheric dynamics via the weakening of convection and the inhibition of cloud forming. In order to be able to fully understand and parameterize this throughout the atmosphere, a detailed vertical profile of the aerosol induced surface cooling and atmospheric heating is required. To get a vertical profile like this, detailed vertically resolved data on aerosol optical properties are required. Such data have now become available from CALIOP lidar onboard CALIPSO satellite. Its near-nadir viewing geometry allows for viewing curtains of the atmosphere, thereby defining with sufficient accuracy the vertical position of aerosols and clouds. In this study, CALIOP Level 2-Version 3 Layer and Profile data for the Mediterranean region from January 2007 to December 2011 have been used. The Mediterranean region was chosen, as it is an area with a mixture of aerosol types, both natural and anthropogenic, where aerosol radiative effects take large values. Furthermore, it is in the proximity of Sahara desert dust, making the area one with large aerosol load. The original CALIOP data have been regridded at a 1�x1� latitude-longitude resolution and at 160 vertical layers. The use of both Layer and Profile data has enabled the derivation of useful 'climatological' products, like spatial properties of aerosol layers, as well as optical properties of them. A comparison with the recently distributed (December 2011) CALIOP Level 3 data, as well as with other satellite data, is presented. Initial results, in agreement with previous studies, reveal that CALIOP aerosol optical depth (AOD) is biased low by around 20%, when compared to other satellite products, such as MODIS. The regridded data are subsequently used in a spectral radiative transfer model and the vertical profile of direct radiative effect is computed. From that, a vertical heating rate profile due to aerosols is derived for each model grid. The geographical and seasonal variability of these rates are investigated, in relation with the corresponding variability of aerosol optical properties. According to preliminary results, the determination of the cooling/heating rate above the surface and within the atmosphere is not affected by the aforementioned bias of CALIOP AOD. The findings of this study are expected to be particularly useful to future studies that deal with the modelling of the aerosol direct, indirect and semi-direct effects (e.g.. Monitoring Atmospheric Composition and Climate II) while the aerosol induced modification of atmospheric lapse rates will be the basis for further studies of aerosol effects on atmospheric dynamics.
Pappas, Vasileios; Hatzianastassiou, Nikos; Matsoukas, Christos; Vardavas, Ilias
Modeling vertical exchange of heat, salt, and other dissolved substances in the Cariaco Basin
A simple 1.5-dimensional model of vertical exchange for heat, salt, and other dissolved substances has been developed for the Cariaco Basin. The model parameters are derived based on the temperature and salinity data collected monthly at a deepwater station in the eastern part of the basin from 1995 through 2007 during the CARIACO time series program. The model describes the processes of turbulent (eddy) diffusion, which includes the integrated effect of diffusive exchange mechanisms acting in the basin, and of vertical advection, which arises following injection of dense water into deep layers following an inflow from the Caribbean Sea. The model takes into account the changes in the horizontal cross-section area of the basin with respect to depth. Temporal variability is an important feature of the hydrography of the Cariaco Basin. To assess profiles of the vertical eddy diffusion coefficient and vertical advection velocity, we examined a time series of CTD profiles (potential temperature and salinity). Two distinct time intervals were identified as the result of this examination. During the first period, the thermohaline structure of the basin was apparently influenced by one or more inflows. The second period, in contrast, showed little or no influence of an inflow. The data from the second period, where no inflows were observed, were incorporated into corresponding transfer equations to assess the profile of the vertical eddy diffusion coefficient, k(z). Then, the result of this assessment was used with the data from the first period to estimate the profile of the vertical advection velocity, W(z), for a time when the effects of an inflow were evident. For that case, the transfer equations include the terms describing the effect of the inflow. Analysis of the vertical profile of the turbulent diffusion coefficient suggests that, in the upper stratified part of the water column, the diffusion mechanism is mostly associated with transient mixing events, which occur due to shear instability in the field of low frequency internal waves. We speculate that below 400 m bottom friction over the sloping bottom and geothermal heat flux play the decisive role in the vertical exchange. Analysis of the W(z) profiles reveals two layers dominated by the entrainment of the ambient fluid into the down flow of dense water from the Caribbean Sea, and two layers where this down flow breaks down through the formation of isopycnal intrusions.
Samodurov, A. S.; Scranton, M. I.; Astor, Y.; Ivanov, L. I.; Chukharev, A. M.; Belokopytov, V. N.; Globina, L. V.
Effect of vertical heat transfer on thermocapillary convection in an open shallow rectangular cavity
In order to understand the effect of the vertical heat transfer on thermocapillary convection characteristics in a differentially heated open shallow rectangular cavity, a series of two- and three-dimensional numerical simulations were carried out by means of the finite volume method. The cavity was filled with the 1cSt silicone oil (Prandtl number Pr = 13.9) and the aspect ratio ranged from 12 to 30. Results show that thermocapillary convection is stable at a small Marangoni number. With the increase of the heat flux on the bottom surface, thermocapillary convection transits to the asymmetrical bi-cellular pattern with the opposite rotation direction. The roll near the hot wall shrinks as the Marangoni number increases. At a large Marangoni number, numerical simulations predict two types of the oscillatory thermocapillary flow. One is the hydrothermal wave, which is dominant only in a thin cavity. The other appears in a deeper cavity and is characterized by oscillating multi-cellular flow. The critical Marangoni number for the onset of the oscillatory flow increases first and then decreases with the increase of the vertical heat flux. The three-dimensional numerical simulation can predict the propagating direction of the hydrothermal wave. The velocity and temperature fields obtained by three-dimensional simulation in the meridian plane are very close to those obtained by two-dimensional simulation.
Li, You-Rong; Zhang, Hong-Ru; Wu, Chun-Mei; Xu, Jin-Liang
Vibration Characteristics of a Vertical Round Tube According to Heat Transfer Regimes
This paper presents the results of an experimental work on the effects of boiling heat transfer regimes on the flow-induced vibration (FIV). The experiment has been performed using an electrically heated vertical round tube through which water flows at atmospheric pressure. Vibration characteristics of the heated tube are changed significantly by heat transfer regimes and flow patterns. For single-phase liquid convection, the rod vibrations are negligible. However, on the beginning of subcooled nucleate boiling at tube exit, vibration level becomes very large. As bubble departure occurs at the nucleation site of heated surface, the vibration decreases to saturated boiling region where thermal equilibrium quality becomes 0.0 at tube exit. In saturated boiling region, vibration amplitude increases with exit quality up to a certain maximum value due to the reinforced turbulence then decreases. At liquid film dryout condition, vibration could be regarded as negligible, however, these results cannot be extended to DNB-type CHF mechanism. Frequency analysis results of vibration signals suggested that excitation sources be different with heat transfer regimes. This study would contribute to improve the understanding of the relationship between boiling heat transfer and FIV. (authors)
Yong Ho Lee; Soon Heung Chang [Korea Advanced Institute of Science and Technology, 373-1, Guseung-dong, Yuseong-ku, Daejeon, 305-701 (Korea, Republic of); Won-Pil Baek [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)
The global response to vertical diabatic heating structures associated with the Madden-Julian oscillation derived from TRMM estimates
The anomalous global atmospheric circulation associated with the Madden-Julian oscillation (MJO) is examined using composite vertical anomalous diabatic heating structures based on Tropical Rainfall Measuring Mission (TRMM) estimates and reanalysis datasets and integrating a primitive equations model. Variations in the dynamical response from the observational and reanalysis products are investigated in relation to the detailed structure of the vertical structure of heating of the MJO, with specific focus of the role of the westward tilting with altitude in the heating, clearly evident in three reanalysis heating structures but is less well pronounced in the TRMM heating structures. It was found that the atmospheric response to the reanalysis heatings were far more consistent compared to the responses from the TRMM heating estimates. Examination of the moisture flux during the main active phase of the MJO revealed a surplus in moisture convergence ahead of the anomalous heating from each of the reanalysis integrations, which was found to be directly attributed to the vertical tilt in heating structure. In contrast, the response to the TRMM heatings showed no phase shift in moisture convergence in relation to the convective heating and was understood to be a consequence of the weaker representation of vertical tilting in heating structure. It was suggested that the westward tilt in heating could therefore play an important role in promoting convection east of the main heating region. The dynamical response to composite vertical diabatic heating structures associated with the MJO from simulations with Unified Model (UM) HadGEM3 with standard and enhanced (x1.5) entrainment rates are also examined to investigate the relationship between the dynamical response to the heating profile and quality of MJO simulations.
Taylor, J.; Woolnough, S.; Inness, P.
A parametrical study on the energetic and exergetic assessment of a solar-assisted vertical ground-source heat pump system used for heating a greenhouse
An energetic and exergetic modeling of a solar-assisted vertical ground-source heat pump (GSHP) greenhouse heating system (SAGSHPGHS) for system analysis and performance assessment is presented in this study. Energy (heating coefficient of performance �COP�) and exergy efficiencies at various reference and entering water temperatures are also determined. The actual thermal data collected are utilized for the model calculations at different
Onder Ozgener; Arif Hepbasli
Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube
The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, in=130 to 161K), the inlet pressure (Pin=812 to 1315kPa), the dissolved oxygen concentration (O2=5.88 and 7.34ppm) and the increasing heat input (Q0exp(t\\/tau), tau=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test
Koichi Hata; Masahiro Shiotsu; Nobuaki Noda
Comparison of practical vertical ground heat exchanger sizing methods to a Fort Polk data/model benchmark.
The results of five practical vertical ground heat exchanger sizing programs are compared against a detailed simulation model that has been calibrated to monitored data taken from one military family housing unit at Fort Polk, Louisiana. The assertion tha...
J. W. Thornton T. P. McDowell P. J. Hughes
Buoyant instabilities in downward flow in a symmetrically heated vertical channel
This study of the downward flow of nitrogen in a tall, partially heated vertical channel (upstream isothermal at T{sub in}*, heated region isothermal at T{sub s}* downstream adiabatic) shows the strong effects of buoyancy even for small temperature differences. Time-dependent oscillations including periodic flow reversals occur along the channel walls. Although the flow and heat transfer are asymmetric, the temperature and axial component of velocity show symmetric reflections at two times that are half a period apart and the lateral component of velocity shows antisymmetric reflections at the two times. There is strong interaction between the downward flow in the central region of the channel and the upward flow along the heated channel walls. At the top of the heated region, the upward buoyant flow turns toward the center of the channel and is incorporated into the downward flow. Along the channel centerline there are nonmonotonic variations of the axial component of velocity and temperature and a large lateral component of velocity that reverses direction periodically. Results are presented for Re = 219.7 and Gr/Re{sup 2} = 1.83, 8.0, and 13.7. The heat transfer and the frequency of the oscillations increases and the flow and temperature fields become more complex as Gr/Re{sup 2} increases. The results have applications to fiber drying, food processing, crystal growth, solar energy collection, cooling of electronic circuits, ventilation, etc.
Evans, G. [Sandia National Lab., Livermore, CA (United States); Greif, R. [Univ. of California, Berkeley, CA (United States)
Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium
PubMed Central
The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size.
Natural convection heat transfer of nanofluids along a vertical plate embedded in porous medium.
The unsteady natural convection heat transfer of nanofluid along a vertical plate embedded in porous medium is investigated. The Darcy-Forchheimer model is used to formulate the problem. Thermal conductivity and viscosity models based on a wide range of experimental data of nanofluids and incorporating the velocity-slip effect of the nanoparticle with respect to the base fluid, i.e., Brownian diffusion is used. The effective thermal conductivity of nanofluid in porous media is calculated using copper powder as porous media. The nonlinear governing equations are solved using an unconditionally stable implicit finite difference scheme. In this study, six different types of nanofluids have been compared with respect to the heat transfer enhancement, and the effects of particle concentration, particle size, temperature of the plate, and porosity of the medium on the heat transfer enhancement and skin friction coefficient have been studied in detail. It is found that heat transfer rate increases with the increase in particle concentration up to an optimal level, but on the further increase in particle concentration, the heat transfer rate decreases. For a particular value of particle concentration, small-sized particles enhance the heat transfer rates. On the other hand, skin friction coefficients always increase with the increase in particle concentration and decrease in nanoparticle size. PMID:23391481
Uddin, Ziya; Harmand, Souad
Two-phase distribution in the vertical flow line of a domestic wet central heating system
The theoretical and experimental aspects of bubble distribution in bubbly two-phase flow are reviewed in the context of the micro bubbles present in a domestic gas fired wet central heating system. The latter systems are mostly operated through the circulation of heated standard tap water through a closed loop circuit which often results in water supersaturated with dissolved air. This leads to micro bubble nucleation at the primary heat exchanger wall, followed by detachment along the flow. Consequently, a bubbly two-phase flow characterises the flow line of such systems. The two-phase distribution across the vertical and horizontal pipes was measured through a consideration of the volumetric void fraction, quantified through photographic techniques. The bubble distribution in the vertical pipe in down flow conditions was measured to be quasi homogenous across the pipe section with a negligible reduction in the void fraction at close proximity to the pipe wall. Such a reduction was more evident at lower bulk fluid velocities.
Fsadni, A.-M.; Ge, Y. T.
Downflow heat transfer in a heated ribbed vertical annulus with a cosine power profile
Experiments designed to investigate downflow heat transfer in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine power profile and a flat azimuthal power shape. Data presented in this report are from the ECS-2c series, which was a follow on series to the ECS-2b series, conducted specifically to provide additional data on the effect of different powers at the same test conditions, for use in evaluation of possible power effects on the aluminum temperature measurements. Electrical powers at 90%, 100%, and 110% of the power required to result in the maximum aluminum temperature at fluid saturation temperature were used at each set of test conditions previously used in the ECS-2b series. The ECS-2b series was conducted in the same test rig as the previous ECS-2b series. Data and experimental description for the ECS-2b series is provided in a previous report. 18 refs., 25 figs., 3 tabs.
Anderson, J.L.; Condie, K.G.; Larson, T.K.
Characterization of heat loads from mitigated and unmitigated vertical displacement events in DIII-D
Experiments have been conducted on the DIII-D tokamak to study the distribution and repeatability of heat loads and vessel currents resulting from vertical displacement events (VDEs). For unmitigated VDEs, the radiated power fraction appears to be of order 50%, with the remaining power dominantly conducted to the vessel walls. Shot-to-shot scatter in heat loads measured at one toroidal location is not large (<�50%), suggesting that toroidal asymmetries in conducted heat loads are not large. Conducted heat loads are clearly observed during the current quench (CQ) of both mitigated and unmitigated disruptions. Significant poloidal asymmetries in heat loads and radiated power are often observed in the experiments but are not yet understood. Energy dissipated resistively in the conducting walls during the CQ appears to be small (<5%). The mitigating effect of neon massive gas injection (MGI) as a function of MGI trigger delay has also been studied. Improved mitigation is observed as the MGI trigger delay is decreased. For sufficiently early MGI mitigation, close to 100% radiated energy and a reduction of roughly a factor 2 in vessel forces is achieved.
Hollmann, E. M.; Moyer, R. A. [University of California-San Diego, La Jolla, California 92093 (United States)] [University of California-San Diego, La Jolla, California 92093 (United States); Commaux, N.; Jernigan, T. J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Eidietis, N. W.; Humphreys, D. A.; Strait, E. J.; Wesley, J. C. [General Atomics, San Diego, California 92186 (United States)] [General Atomics, San Diego, California 92186 (United States); Lasnier, C. J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Pitts, R. A.; Sugihara, M. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France)] [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France); Watkins, J. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)
Vertical single-wall carbon nanotube forests as plasmonic heat pipes.
High thermal conductivity of carbon nanotubes (NTs) is attractive for the heat removal applications. However, the problem of efficient thermal coupling to the heater/cooler still needs to be resolved. We study near-field electromagnetic tunneling as a mechanism of heat transfer across the interface. We report interface thermal (Kapitza) conductance between a low-density vertical metallic single-wall NT forest and a quartz substrate on the order of 50 MW/Km(2) and explain it by strong electromagnetic interaction and near-field entanglement between the surface phonon-polaritons in the polar dielectric and the NT plasmons. We predict that the thickness of the NT film can be tweaked to the resonance wavelength of these entangled modes for performance optimization of nanocarbon thermal interconnects. PMID:22480248
Nemilentsau, Andrei M; Rotkin, Slava V
Radiative heating characteristics of Earth's cloudy atmosphere from vertically resolved active sensors
Haynes, John M.; Vonder Haar, Thomas H.; L'Ecuyer, Tristan; Henderson, David
Instability of mixed convection in a vertical porous channel with uniform wall heat flux
Mixed convection in a vertical plane channel filled with a saturated porous medium is investigated. The boundary planes are considered as subject to symmetric uniform heat fluxes, resulting into a net fluid heating or cooling. Either upflow or downflow conditions are considered, thus exhibiting two distinct regimes: buoyancy-assisted and buoyancy-opposed. A basic stationary and parallel flow directed vertically along the channel is examined. The linear stability of this basic solution is developed through the standard normal-mode analysis. The solution of the eigenvalue problem for neutral stability is carried out numerically for the general oblique modes. An analytical solution is provided for the longitudinal modes, with a horizontal wave vector having a direction parallel to the boundary planes. An asymptotic analytical solution is also allowed for oblique modes with either a vanishingly small P�clet number or a vanishingly small wave number. The longitudinal modes are the most unstable, displaying their parametric domain of instability under buoyancy-opposed regime. In this regime, the longitudinal modes with sufficiently small wave numbers are always unstable. This conclusion suggests that conditions of flow reversal or crossing of parametric singularities, characteristic of the parallel flow solution under buoyancy-opposed regime, are unlikely to be observed in an experiment.
Barletta, A.
Vertical profiles of aerosol extinction and radiative heating at Niamey, Niger
Land use and land cover changes may lead to increases in Saharan dust outbreaks and increased dust aerosol loading in the atmosphere. It is important to understand the impact of Saharan dust on the Earth's radiation budget in order to improve model simulations of regional and global climate. Details of the radiative impact depend on the amount, vertical profile, and optical properties of the observed aerosol. The ARM Mobile Facility (AMF) was deployed in Niamey, Niger during 2006 as part of the RADAGAST project (Radiative Atmospheric Divergence using ARM Mobile Facility, GERB data and AMMA Stations) in cooperation with the African Monsoon Multidisciplinary Analysis (AMMA) experiment. This deployment represents the first long- term series of measurements of aerosol properties from the surface in the Sahel region and provides an unprecedented opportunity to examine the radiative heating profiles associated with aerosol in this region. Using aerosol optical properties derived from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) and the Atmospheric Emitted Radiance Interferometer (AERI), profiles of relative aerosol extinction from the micropulse lidar (MPL), and measurements of broadband surface radiation at the AMF site, we examine the vertical profile of aerosol extinction and aerosol radiative heating during the dry season (January - March and Oct-Dec, 2006) at Niamey.
McFarlane, S.; Kassianov, E.; Flynn, C.; Barnard, J.
Mixed Convection with Conduction and Surface Radiation from a Vertical Channel with Discrete Heating
A numerical investigation into fluid flow and heat transfer for the geometry of a vertical parallel plate channel subjected to conjugate mixed convection with radiation is attempted here. The channel considered has three identical flush-mounted discrete heat sources in its left wall, while the right wall that does not contain any heat source acts as a sink. Air, assumed to be a radiatively non-participating and having constant thermophysical properties subject to the Boussinesq approximation, is the cooling agent. The heat generated in the left wall gets conducted along it and is later dissipated by mixed convection and radiation. The governing equations, considered in their full strength sans the boundary layer approximations, are converted into vorticity-stream function form and are then normalized. These equations along with pertinent boundary conditions are solved through finite volume method coupled with Gauss-Seidel iterative technique. The effects of modified Richardson number, surface emissivity, thermal conductivity and aspect ratio on local temperature distribution along the channel, maximum channel temperature and relative contributions of mixed convection and radiation have been thoroughly studied. The prominence of radiation in the present problem has been highlighted.
Londhe, S. D.; Rao, C. G.
The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels
This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.
Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.
Vertical Variations In Heat Flow Inferred From Experiments In Deep Boreholes
Deep scientific and parametric continental boreholes allow to obtain representative experimental data on combination of the geothermal parameters of the crust - temperature, temperature gradient, rock thermal properties, and, as the result, heat flow density values - which are more reliable compared to the previous data from shallow boreholes. Special advantages of the scientific boreholes include also a possibility for many repeated temperature logging during long time intervals (several years often) after a finish of the drilling that allowed (1) to determine temperatures and temperature gradient values corresponding to thermal equilibrium of the formations studied, (2) to study temporal regularities in temperature and temperature gradient behaviour within different formation layers during the formation recovery process. Scientific boreholes are drilled with numerous coring (often - with continuous coring) that provides the possibility to obtain detailed information on a distribution of rock thermal conductivity along the borehole. As a result, the scientific deep and super-deep boreholes provided the unique possibility for the determination of vertical distributions of the heat flow density that can not be reached normally in other boreholes. Experimental geothermal and petrothermal investigations performed for the super-deep boreholes Kola, Ural, Vorotilovo, Tyumen, Yen-Yakha (all - Russia), Saatly (Azerbaidzhan), and deep scientific and parametric boreholes Kolva, Timano-Pechora, Tyrnyaus, (all - Russia), Krivoy Rog (Ukraine), Muruntau (Uzbekistan), Nordlingen-72 (Germany), Yaxcopoil-1 (Mexico) allowed us to establish the following important peculiarities in geothermal parameters of the crustal blocks studied with scientific deep drilling were established from the investigations: (1) temperature gradient recovery up to undisturbed values occurs essentially faster than it was assumed earlier; (2) a rate of temperature gradient recovery was found to be different for different formation layers; (3) significant variations in rock thermal properties vary significantly along boreholes within several thousands, hundreds and dozens meters as well as along short depth intervals of 0.5-1 m; (4) conductive component of the heat flow density varies up to 70-100% along boreholes often, regular increase in heat flow density within depth intervals of several kilometers is combined with essential local variations, (5) values of a conductive component of the heat flow density established from the measurements in deep and super-deep boreholes exceeds significantly (by 30-100%) and systematically the previous experimental estimates done earlier for shallow boreholes. The mentioned regularities in behaviour of the geothermic parameters were confirmed from new experimental data for the scientific and parametric boreholes Severo-Molokovo, Vysokovo, Yarudeyskaya (Russia), Eyreville (USA) and from the revision of previous experimental geothermic data for the Moscow syneclise (the East European platform) and Ural region. The new results obtained from studying vertical variations in the heat flow density demonstrate a regular essential (30-60%) increase in the conductive component of the heat flow density with a depth within upper depth intervals up to 2000-3000 m. The results show that the determination of heat flow values from averaging the geothermal parameters within long depth intervals can lead to essential underestimation of the crustal heat flow values.
Popov, Y.; Romushkevich, R.; Gorobtsov, D.; Korobkov, D.
Economic potential of vertical ground-source heat pumps compared to air-source air conditioners in South Africa
This study was undertaken to compare the economic viability in Johannesburg, R.S.A., of vertical ground-source and air-source systems. Capital costs and optimum borehole length of the ground system were determined. Monthly heating and cooling capacities, and COPs were evaluated to determine running costs. Payback periods, net present values and internal rates of return were computed. The vertical ground-source system was
P. J. Petit; J. P. Meyer
Nonlinear dynamics between two differentially heated vertical plates in the presence of stratification
We consider the numerical simulation of the flow between infinite, differentially heated vertical plates with positive stratification. We use a two-dimensional Boussinesq approximation, with periodic boundary conditions in the vertical direction. The relative stratification parameter {?=(1/4Ra S)^{1/4}} , where Ra is the Rayleigh number and S the adimensional stratification, is kept constant and equal to 8. The Prandtl number is 0.71. We derive a complex Ginzburg-Landau equation from the equations of motion. Coefficients are computed analytically, but we find that the domain of validity of these coefficients is small and rely on the numerical simulation to adjust the coefficients over a wider range of Rayleigh numbers. We show that the Ginzburg-Landau equation is able to accurately predict the characteristics of the periodic solution at moderate Rayleigh numbers. Above the primary bifurcation at Ra = 1.63 � 105, the Ginzburg-Landau model is found to be Benjamin-Feir unstable and to be characterized by modulated traveling waves and phase-defect chaos, which is supported by evidence from the DNS. As the Rayleigh number is increased beyond Ra = 2.7 � 105, nonlinearities become strong and the flow is characterized by cnoidal waves.
Podvin, B�reng�re; Le Qu�r�, Patrick
Limitation enhancement of a mixed convection by a vibrational heat surface in a vertical channel
A numerical simulation is performed to study effects of a vibrational heat surface on a mixed convection in a vertical channel flow. This subject is a kind of moving boundary problems, and the finite element method and arbitrary Lagrangian Eulerian kinematics description method is then utilized. The main parameters of Grashof number, amplitude and frequency are taken into consideration, and the Reynolds number is limited and equals 100. According to the results, the equations of the critical vibration frequency could be derived and expressed in terms of Grashof number and amplitude. In the forced convection, the critical vibration frequency is only dependent on the amplitude, and in the mixed convection the critical vibration frequency becomes larger as the Grashof number increases. The variation of the critical vibration frequency of the study could league with the critical vibration frequency of the natural convection shown in the previous study consistently.
Fu, Wu-Shung; Huang, Chien-Ping
Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Downward in a Small Diameter Tube
Experiments were performed on boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically downward in a copper smooth tube of 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2�s), heat fluxes from 1 to 16 kW/m2 and quality from 0.1 to over 1 at evaporation temperature of 10�C. Pressure drops were measured and flow patterns were observed at mass fluxes from 30 to 200 kg/(m2�s) and quality from 0.1 to 0.9. The characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified by comparing the measurements with the data for the vertically upward flow previously obtained.
Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu
Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile
The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth�s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.
Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert
Vertical ocean heat fluxes beneath Linear Kinematic Features: a potential mechanism for rapid sea-ice decline in the Arctic
The Cold Halocline Layer is known to provide a strong barrier to vertical exchange in the surface Arctic ocean. We show modelling evidence, supported by observations, for strong Ekman pumping velocities beneath active leads, where discontinuity in the sea-ice drifts and the surface ice-ocean stresses momentum transfer are present. On Figure 1 shown an example of the lead opening. The anomalous vertical velocities beneath the leads extend hundreds of meters below the surface, well into the Atlantic Layer, and bring up large amount of ocean heat (of the order of hundred's of W/m2) into the mixed layer (see Figure 2 - cross section of the lead from Figure 1). We use a high resolution (4 km) general circulation model with a good representation of the CHL and NSTM (the MITgcm). Results show vertical ocean heat fluxes in winter of approximately 3 W/m2 when averaged over the ice-covered Arctic ocean which is equivalent to 15 cm sea-ice melt during a year. We suggest that this process is important in controlling the Arctic sea-ice mass balance and a potentially important player in the recent sea-ice decline - one that is not represented in lower-resolution global climate models. In a future climate with thinner and more mobile pack ice, this contribution from the ocean will only amplify. a) - Sea-ice shear strain rate, day-1 b) - vertical advective ocean heat flux, W/m2 at 40 m depth, c) - sea-ice stress curl, s-1 and d) - sea-ice divergence, s-1. Vertical section across the sea-ice lead of vertical velocity in m/day (a), temperature in oC (b) and vertical advective ocean heat flux in W/m2 (c).
Slavin, A.; Tremblay, B.; Straub, D.
Vertical Profiles of Latent Heating in TRMM: Validation and Assimilation in the GEOS Data Assimilation System. [Year 2001 Project Report
I have derived the vertical profiles of apparent heating Q and Q2 by using 3-hourly balloon sounding data from the ARM SGP sounding array for three IOPs in 2000. These IOPs cover the periods from 3/1 to 3/22, from 9/25 to 10/8, and from 11/27 to 12/22. These heating profiles will be collocated with the TRMM heating profiles for validation studies once the TRMM profiles become available to the investigators. I have also produced the objective analyses of Q1, Q2 and forcing fields for the international GCSS Case 3 Intercomparison project. The GSFC CRM participated in study, based on which TRMM heating profiles are derived. I have also studied to assimilate the vertical heating profile by constraining the cloud-base mass flux in the cumulus convection scheme using the CCM3. I first derive the vertical heating profile for each convective plume of unit cloud-base mass flux. The observed heating profile form ARM is then de-convoluted to derive the cloud base mass fluxes of all individual plumes. These fluxes are compared with those derived from the quasi-equilibrium hypothesis. They are shown to improve many other aspects of the model behavior.
Zhang, Ming-Hua
Mixed convection heat transfer inside a vertical circular cylinder has been experimentally studied for upward and downward flows for hydrodynamically fully developed and thermally developing laminar air flow under constant wall heat flux boundary conditions for Reynolds number range from 400�1600 and the Grashof number range from 1.1 � 10�7.4 � 10. The effects of the cylinder inclination angle and
H. A. Mohammed; Y. K. Salman
Open-cycle absorption solar cooling: Natural convection heat and mass transfer from falling films in vertical channels
In the design of solar collector/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation mtes and solution temperatures is of paramount importance in determining overall cycle performance. The governing equations for natural convection flow in a vertical channel bounded by a heated falling film (simulating a glazed collector/regenerator) were solved using several different finite difference techniques. The numerical results were validated against existing experimental and numerical results for simplified boundary conditions. The appropriate nondimensionalization for the falling film boundary condition was established, ostensibly for the first time, and a parametric study for an air-water vapor mixture has been presented. Curve fits to the numerical results were determined for engineering design applications. To further confirm the validity of the numerical solutions, an experimental apparatus was constructed using electric resistance heat to simulate the constant heat flux of the solar source. Water was introduced at the top of this heated vertical surface at various flow rates and under various supplied heat fluxes, and a natural convection channel flow generated between the heated falling film and a parallel, plexiglas surface. Film temperatures and moist air velocity profiles were measured at various streamwise (vertical) locations for comparison with the numerical results.
Buck, G.A.; Wood, B.D.
Open-cycle absorption solar cooling: Natural convection heat and mass transfer from falling films in vertical channels. Final report
Transient Free Convection Fluid Flow in a Vertical Microchannel as Described by the Hyperbolic Heat Conduction Model
The transient hydrodynamics and thermal behaviors of fluid flow in an open-ended vertical parallel-plate microchannel are investigated analytically under the effect of the hyperbolic heat conduction model. The model that combines both the continuum approach and the possibility of slip at the boundary is adopted in this study. The effects of Knudsen number Kn and thermal relaxation time ? on
A. F. Khadrawi; Ali Othman; M. A. Al-Nimr
Effect of insulated\\/uninsulated channel walls on heat transfer from a horizontal finned tube in a vertical channel
Measurements were made of the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom. In one set of experiments, both walls of the channel were heavily insulated, while in a second set of experiments, one of the insulated walls was replaced by an uninsulated metallic sheet.
E. M. Sparrow; M. A. Ansari
Numerical modeling of a 2 K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1
Fermilab Vertical Test Stand-1 (VTS-1) has been in operation since 2007 for testing superconducting radio frequency (SCRF) cavities at 2 K. This test stand includes a heat exchanger consisting of a single layer; helically wound finned tube, upstream of the J-T valve. A finite difference thermal model has been developed in Engineering Equation Solver (EES) to study the thermal performance of this heat exchanger during refilling of the test stand. The model can predict heat exchanger performance under various other operating conditions and is therefore useful as a design tool for similar heat exchangers in other facilities. The present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have been compared with experimental data gathered from the VTS-1 heat exchanger, and they are in good agreement with the present model.
Gupta, Prabhat Kumar; Rabehl, Roger
Magnetohydrodynamic non-Darcy mixed convection heat transfer from a vertical heated plate embedded in a porous medium with variable porosity
A numerical model is developed to study magnetohydrodynamics (MHD) mixed convection from a heated vertical plate embedded in a Newtonian fluid saturated sparsely packed porous medium by considering the variation of permeability, porosity and thermal conductivity. The boundary layer flow in the porous medium is governed by Forchheimer�Brinkman extended Darcy model. The conservation equations that govern the problem are reduced
Dulal Pal
Nonlinear time series analysis and clustering for jet axis identification in vertical turbulent heated jets.
In the present work we approach the hydrodynamic problem of discriminating the state of the turbulent fluid region as a function of the distance from the axis of a turbulent jet axis. More specifically, we analyzed temperature fluctuations in vertical turbulent heated jets where temperature time series were recorded along a horizontal line through the jet axis. We employed data from different sets of experiments with various initial conditions out of circular and elliptical shaped nozzles in order to identify time series taken at the jet axis, and discriminate them from those taken near the boundary with ambient fluid using nonconventional hydrodynamics methods. For each temperature time series measured at a different distance from jet axis, we estimated mainly nonlinear measures such as mutual information combined with descriptive statistics measures, as well as some linear and nonlinear dynamic detectors such as Hurst exponent, detrended fluctuation analysis, and Hjorth parameters. The results obtained in all cases have shown that the proposed methodology allows us to distinguish the flow regime around the jet axis and identify the time series corresponding to the jet axis in agreement with the conventional statistical hydrodynamic method. Furthermore, in order to reject the null hypothesis that the time series originate from a stochastic process, we applied the surrogate data method. PMID:24730919
Charakopoulos, A K; Karakasidis, T E; Papanicolaou, P N; Liakopoulos, A
Transient Buoyancy Induced Flow Adjacent to a Uniformly Heated Vertical Surface
Transient buoyancy induced flows, adjacent to a uniformly heated vertical surface, are determined by numerically solving Navier-Stokes equations. A finite difference code has been developed. The numerical results agree very well with previous analytic solutions and experimental data. In such flows, the downstream propagation of the Leading Edge Effect (LEE) is a dominant process. Large fluctuations arise in the temporal evolution of the temperature, velocity and motion pressure fields. For air of Pr = 0.72, relevant flow instability characteristics are quantitatively analyzed, as functions of downstream location. These temporal fluctuations are manifested as core structures, in the fields of horizontal velocity V and motion pressure. The regional features of these structures are determined in detail. Results indicate that the LEE propagation involves two distinctive processes. One is the propagation of the LEE front, into the one-dimensional diffusive downstream flow. The second process is the propagation of the following LEE, into two-dimensional convective downstream flow. The phase angle of the temperature effect leads those of the velocities U and V. This indicates that such flows are buoyancy induced. This buoyancy also induces an in-flowing motion pressure field in the region near the surface. The pressure effect is negligible inside the boundary layer region. However, the pressure field extends into the ambient fluid. There, the pressure force drives a transient entrainmental flow toward surface.
Wu, Lixing
Higher order stability effects in a natural convection boundary layer over a vertical heated wall
The stability of a laminar boundary layer flow under natural convection on a vertical isothermally heated wall is studied analytically. The analysis is performed by using two different two-dimensional linear models: (1) The non-parallel flow model in which the steady mean flow as well as the disturbance amplitude functions can change in the streamwise direction; (2) The parallel flow model in which the effects of the mean flow and disturbance changes in the streamwise direction are neglected. The linear non-parallel stability analysis is based on the so-called parabolised stability equations (PSEs) which have been successfully applied to the stability analysis of forced convection boundary layers. In this study the PSE equations are applied to natural convection boundary layers in order to show the difference between parallel and non-parallel stability analysis. A second part of this study deals with the effects of variable properties, which are always present in natural convection flows. They are analysed by an extended version of the Orr-Sommerfeld equation (EOSE).
Severin, J.; Herwig, H.
Multiple buoyancy driven flows in a vertical cylinder heated from below
The structure of axisymmetric buoyancy-driven convection in a vertical cylinder heated from below is probed by finite element solution of the Boussinesq equations coupled with computed-implemented perturbation techniques for detecting and tracking multiple flows and for determining flow stability. Results are reported for fluids with Prandtl number of one and for cylinders with aspect ratio (Lambda) (defined as the height to radius of the cylinder) between 0.5 and 2.25. Extensive calculations of the neutral stability curve for the static solution and of the nonlinear motions along the bifurcating flow families show a continuous evolution of the primary cellular motion from a single toroidal cell to two and three cells nested radially in the cylinder, instead of the sharp transitions found for a cylinder with shear-free sidewalls. The smooth transitions in flow structure with Rayleigh number and lambda are explained by nonlinear connectivity between the first two bifurcating flow families formed either by a secondary bifurcation point for Lambda or = Lambda * approximately 0.80 or by a limit point for Lambda Lambda *. The transition between these two modes may be described by the theory of multiple limit point bifurcation.
Yamaguchi, Y.; Chang, C. J.; Brown, R. A.
Transition to chaos of natural convection between two infinite differentially heated vertical plates.
Natural convection of air between two infinite vertical differentially heated plates is studied analytically in two dimensions (2D) and numerically in two and three dimensions (3D) for Rayleigh numbers Ra up to 3 times the critical value Ra(c)=5708. The first instability is a supercritical circle pitchfork bifurcation leading to steady 2D corotating rolls. A Ginzburg-Landau equation is derived analytically for the flow around this first bifurcation and compared with results from direct numerical simulation (DNS). In two dimensions, DNS shows that the rolls become unstable via a Hopf bifurcation. As Ra is further increased, the flow becomes quasiperiodic, and then temporally chaotic for a limited range of Rayleigh numbers, beyond which the flow returns to a steady state through a spatial modulation instability. In three dimensions, the rolls instead undergo another pitchfork bifurcation to 3D structures, which consist of transverse rolls connected by counter-rotating vorticity braids. The flow then becomes time dependent through a Hopf bifurcation, as exchanges of energy occur between the rolls and the braids. Chaotic behavior subsequently occurs through two competing mechanisms: a sequence of period-doubling bifurcations leading to intermittency or a spatial pattern modulation reminiscent of the Eckhaus instability. PMID:24032927
Gao, Zhenlan; Sergent, Anne; Podvin, Berengere; Xin, Shihe; Le Qu�r�, Patrick; Tuckerman, Laurette S
Measuring the electrical properties of soil using a calibrated ground-coupled GPR system
USGS Publications Warehouse
Traditional methods for estimating vadose zone soil properties using ground penetrating radar (GPR) include measuring travel time, fitting diffraction hyperbolae, and other methods exploiting geometry. Additional processing techniques for estimating soil properties are possible with properly calibrated GPR systems. Such calibration using ground-coupled antennas must account for the effects of the shallow soil on the antenna's response, because changing soil properties result in a changing antenna response. A prototype GPR system using ground-coupled antennas was calibrated using laboratory measurements and numerical simulations of the GPR components. Two methods for estimating subsurface properties that utilize the calibrated response were developed. First, a new nonlinear inversion algorithm to estimate shallow soil properties under ground-coupled antennas was evaluated. Tests with synthetic data showed that the inversion algorithm is well behaved across the allowed range of soil properties. A preliminary field test gave encouraging results, with estimated soil property uncertainties (????) of ??1.9 and ??4.4 mS/m for the relative dielectric permittivity and the electrical conductivity, respectively. Next, a deconvolution method for estimating the properties of subsurface reflectors with known shapes (e.g., pipes or planar interfaces) was developed. This method uses scattering matrices to account for the response of subsurface reflectors. The deconvolution method was evaluated for use with noisy data using synthetic data. Results indicate that the deconvolution method requires reflected waves with a signal/noise ratio of about 10:1 or greater. When applied to field data with a signal/noise ratio of 2:1, the method was able to estimate the reflection coefficient and relative permittivity, but the large uncertainty in this estimate precluded inversion for conductivity. ?? Soil Science Society of America.
Oden, C. P.; Olhoeft, G. R.; Wright, D. L.; Powers, M. H.
An experimental study on flow patterns and heat transfer characteristics during cryogenic chilldown in a vertical pipe
In the present paper, the experimental results of a cryogenic chilldown process are reported. The physical phenomena involve unsteady two-phase vapor-liquid flow and intense boiling heat transfer of the cryogenic fluid that is coupled with the transient heat conduction inside pipe walls. The objective for the present study is to compare the chilldown rates and flow patterns between the upward flow and downward flow in a vertical pipe. Liquid nitrogen is employed as the working fluid and the test section is a vertical straight segment of a Pyrex glass pipe with an inner diameter of 8 mm. The effects of mass flow rate on the flow patterns, heat transfer characteristics and interface movement were determined through experiments performed under several different mass flow rates. Through flow visualization, measurement and analysis on the flow patterns and temperature variations, a physical explanation of the vertical chilldown is given. By observing the process and analyzing the results, it is concluded that pipe chilldown in a vertical flow is similar to that in microgravity to some extent.
Hu, Hong; Chung, Jacob N.; Amber, Samuel H.
An investigation of heat exchange of liquid metal during flow in a vertical tube with non-uniform heating in the transverse magnetic field
The results of experimental investigations of heat exchange during the downflow of liquid metal in a vertical tube with non-uniform heating in the transverse magnetic field are presented. The experiment was more realistic in terms of conditions of the blanket of a fusion reactor of the tokamak type. Profiles of the average temperature, distribution of local and mean heat transfer coefficients (Nusselt numbers), and the intensities and spectra of temperature pulsations have been measured. On certain combinations of operating parameters in the strong magnetic field low-frequency temperature pulsations with abnormal intensity were found.
Mel'nikov, I. A.; Razuvanov, N. G.; Sviridov, V. G.; Sviridov, E. V.; Shestakov, A. A.
Natural convection and radiation heat transfer of an externally-finned tube vertically placed in a chamber
A three-dimensional numerical study was made to investigate effects of fin angle, fin surface emissivity, and tube wall temperature on heat transfer enhancement for a longitudinal externally-finned tube placed vertically in a small chamber. The numerical model was first validated through comparison with experimental measurements and the appropriateness of general boundary conditions was examined. The numerical results show that the mean Nusselt number increases with Rayleigh number for all the fin angles investigated. The maximum heat transfer rate per mass occurs when the fin angle is about 60� for fin surface emissivity between 0.7 and 0.8 and 55� when the surface emissivity increases to 0.9. With increasing tube wall temperature, both the natural convection and radiation heat transfer are enhanced, but the fraction of radiation heat transfer decreases in the temperature range studied. Radiation fraction increases with increasing fin surface emissivity. Both convection and radiation heat transfer modes are important.
Qiu, Yan; Tian, Maocheng; Guo, Zhixiong
An effective numerical technique for entry length laminar convective heat transfer in vertical and horizontal ducts of any cross section
A numerical technique is developed for predicting the temperature and velocity distributions in vertical ducts formed between parallel plates and vertical and horizontal ducts of circular and rectangular cross-section. This technique solves the energy (Fourier) equation, and the solution is then coupled with the momentum (Navier) and continuity equations. This technique has been employed to determine the laminar fluid flow and specified constant wall heat tranfer rate. The method is dependent upon the heat transfer fluid having a high Prandtl number (typically greater than 10). Such fluids are characterized by highly temperature sensitive thermophysical properties which can be taken fully into account by this technique. It is found that this technique yields results very close to experimental values. In addition, a large saving in computer memory usage and in execution times can be obtained using this technique instead of the conventional full solutions.
Allen, P. H. G.; Szpiro, O.
Constructal optimization of a vertical insulating wall based on a complex objective combining heat flow and strength
For a vertical insulating wall, a product function of heat flow and strength with power weight is introduced as the complex\\u000a optimization objective to compromise between insulating performance and mechanical performance. Under the global constraints\\u000a of fixed external dimensions and safety requirements, the constructal optimization of the wall is carried out by taking the\\u000a complex function maximization as the objective.
ZhiHui Xie; LinGen Chen; FengRui Sun
Non-Darcy mixed convection in a vertical porous channel with discrete heat sources at the walls
A numerical study of mixed convection in a parallel-plate vertical channel filled with a fluid-saturated porous medium and containing discrete heat sources at the walls is performed using the Brinkman-Forchheimer-extended Darcy model. The evolution of buoyancy-assisted mixed convection is examined for both the Darcy and the non-Darcy regimes. The results indicate that as the Darcy number is decreased, the location
A. Hadim; G. Chen
Experimental determination of natural convection heat transfer coefficient in a vertical flat-plate solar air heater
In this study, natural convection heat transfer in a vertical flat-plate solar air heater of 2.5m height and 1m width, with one- and two-glass covers was studied experimentally. Totally six cases of airflow (two for air heater with one glass cover and four for air heater with two-glass covers) were considered. These cases included states that air could flow within
N. Hatami; M. Bahadorinejad
Modeling convection heat transfer and turbulence with flre applications: a high temperature vertical plate and a methane flre
Simulations of the three-dimensional turbulent ?ow and heat transfer adjacent to a large (3 meter) high temperature (up to 860 K) vertical ?at plate and in a large-scale methane ?ame have been made and compared with experimental data. Results are obtained with a Reynolds averaged Navier-Stokes (RANS) v2� f model, a direct numerical simulation (DNS), and a detached eddy simulation
D. Rouson; S. R. Tieszen; G. Evans
Effects of mass transfer on flow past an impulsively started infinite vertical plate with Newtonian heating and chemical reaction
An exact solution to the problem of flow due to the impulsive motion of an infinite vertical plate in its own plane in the presence of i) species concentration, ii) Newtonian heating at the plate, and iii) first-order chemical reaction has been derived by the Laplace transform technique. The influence of various parameters entering into the problem on the velocity field and skin friction for both air and water in the cases of both cooling and heating of the plate is discussed.
Rajesh, V.
MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition
Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement.
Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.
MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.
Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688
Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmed I
Analysis of staggered tube bundle heat transfer to vertical foam flow
In general heat transfer intensity between solid surface and coolant (fluid) depends on three main parameters: heat transfer coefficient, size of heat exchange surface and temperature difference between surface and fluid. Sometimes the last two parameters (surface size and temperature difference) are strictly limited due to the process or technological requirements, and only increase of heat transfer coefficient is allowed.
J. Gylys; S. Sinkunas; T. Zdankus
Retrieved Vertical Profiles of Latent Heat Release Using TRMM Rainfall Products
This paper represents the first attempt to use TRMM rainfall information to estimate the four dimensional latent heating structure over the global tropics for February 1998. The mean latent heating profiles over six oceanic regions (TOGA COARE IFA, Central Pacific, S. Pacific Convergence Zone, East Pacific, Indian Ocean and Atlantic Ocean) and three continental regions (S. America, Central Africa and Australia) are estimated and studied. The heating profiles obtained from the results of diagnostic budget studies over a broad range of geographic locations are used to provide comparisons and indirect validation for the heating algorithm estimated heating profiles. Three different latent heating algorithms, the Goddard Convective-Stratiform (CSH) heating, the Goddard Profiling (GPROF) heating, and the Hydrometeor heating (HH) are used and their results are intercompared. The horizontal distribution or patterns of latent heat release from the three different heating retrieval methods are quite similar. They all can identify the areas of major convective activity (i.e., a well defined ITCZ in the Pacific, a distinct SPCZ) in the global tropics. The magnitude of their estimated latent heating release is also not in bad agreement with each other and with those determined from diagnostic budget studies. However, the major difference among these three heating retrieval algorithms is the altitude of the maximum heating level. The CSH algorithm estimated heating profiles only show one maximum heating level, and the level varies between convective activity from various geographic locations. These features are in good agreement with diagnostic budget studies. By contrast, two maximum heating levels were found using the GPROF heating and HH algorithms. The latent heating profiles estimated from all three methods can not show cooling between active convective events. We also examined the impact of different TMI (Multi-channel Passive Microwave Sensor) and PR (Precipitation Radar) rainfall information on latent heating structures.
Tao, W.-K.; Lang, S.; Olson, W. S.; Meneghini, R.; Yang, S.; Simpson, J.; Kummerow, C.; Smith, E.
Investigations on Water Vapor-Coal Partial Gasification in a Helium Heated Vertical Gas Generator.
Process engineering design and layout strategies for a gas generator in vertical construction (vs. horizontal construction in the past) of the process of water vapor-coal gasification to non-catalytical partial and complete gasification of bituminous coal...
H. Barnert J. Singh H. Hohn G. Romes H. Kalwitzki
Natural Convection in an Enclosure with Discrete Roughness Elements on a Vertical Heated Wall.
Natural convection flow next to a heated wall with single and repeated, two-dimensional, rectangular roughness elements is studied numerically and experimentally. The objective is to determine how these roughness elements influence heat transfer rates fro...
S. Shakerin M. S. Bohn R. I. Loehrke
Ocean Turbulence. Paper 2; One-Point Closure Model Momentum, Heat and Salt Vertical Diffusivities in the Presence of Shear
We develop and test a 1-point closure turbulence model with the following features: 1) we include the salinity field and derive the expression for the vertical turbulent diffusivities of momentum K(sub m) , heat K(sub h) and salt K(sub s) as a function of two stability parameters: the Richardson number R(sub i) (stratification vs. shear) and the Turner number R(sub rho) (salinity gradient vs. temperature gradient). 2) to describe turbulent mixing below the mixed layer (ML), all previous models have adopted three adjustable "background diffusivities" for momentum, heat and salt. We propose a model that avoids such adjustable diffusivities. We assume that below the ML, the three diffusivities have the same functional dependence on R( sub i) and R(sub rho) as derived from the turbulence model. However, in order to compute R(sub i) below the ML, we use data of vertical shear due to wave-breaking.measured by Gargett et al. The procedure frees the model from adjustable background diffusivities and indeed we employ the same model throughout the entire vertical extent of the ocean. 3) in the local model, the turbulent diffusivities K(sub m,h,s) are given as analytical functions of R(sub i) and R(sub rho). 5) the model is used in an O-GCM and several results are presented to exhibit the effect of double diffusion processes. 6) the code is available upon request.
Canuto, V. M.; Howard, A.; Cheng, Y.; Dubovikov, M. S.
Seismic-geodynamic constraints on three-dimensional structure, vertical flow, and heat transfer in the mantle
Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.
Forte, A. M.; Woodward, R. L.
SEMICONDUCTOR MATERIALS: Finite element analysis of the temperature field in a vertical MOCVD reactor by induction heating
The temperature field in the vertical metalorganic chemical vapor deposition (MOCVD) reactor chamber used for the growth of GaN materials is studied using the finite element analysis method (FEM). The effects of the relative position between the coils and the middle section of the susceptor, the radius of the coil, and the height of the susceptor on heating condition are analyzed. All simulation results indicate that the highest heating efficiency can be obtained under the conditions that the coil distributes symmetrically in the middle section of the susceptor and the ratio of the height of the susceptor to that of the coil is three-quarters. Furthermore, the heating efficiency is inversely proportional to the radius of the coil.
Zhiming, Li; Shengrui, Xu; Jincheng, Zhang; Yongming, Chang; Jingyu, Ni; Xiaowei, Zhou; Yue, Hao
Generalized correlaion of critical heat flux for the forced convection boiling in vertical uniformly heated round tubes
The present study deals with the critical heat flux (CHF) in the conditions that the fluid fed to heated tubes is subcooled (including saturated liquid in the extreme situation) with no entrained vapor. To start with, postulating that there is a state where the hydrodynamic condition is responsible for CHF, a theoretical presumption for the generalized correlaion equation of CHF
Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube
Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated tube are experimentally investigated. The double tube test sections are 0.5 m long with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tubes are one smooth tube and two corrugated tubes, which are constructed from smooth copper tube of 8.7 mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20 C, heat fluxes of 20, 25, and 30 kW/m{sup 2}, and mass fluxes of 200, 300, and 400 kg/m{sup 2} s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat flux, mass flux, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated tubes compared with those of the smooth tube are approximately 0-10% and 70-140%, respectively. (author)
Aroonrat, Kanit; Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering, King Mongkut's University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)
Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in a Small Diameter Tube
In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in a copper smooth tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2�s), heat fluxes from 1 to 16 kW/m2 and qualities from 0.1 to over 1 at evaporation temperature of 10�C, and pressure drops were also measured at mass fluxes of 100 and 200 kg/(m2�s) and qualities from 0.1 to 0.9. Three types of flow pattern were observed in the tube: A slug, a slug-annular and an annular flow. Based on the measurements, the characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified. The measured pressure drop and heat transfer coefficient were compared with correlations.
The effect of thermal dispersion on unsteady MHD convective heat transfer through vertical porous
The influence of thermal dispersion on unsteady two-dimensional laminar flow is presented. A viscous incompressible conducting fluid in the vicinity of a semi infinite vertical porous through a moving plate in the presence of a magnetic fluid is studied. A cod (FORTRAN) was constructed for numerical computations for the velocity and temperature for various values of the affected parameters were carried out.
Mohamadien, Ghada F.
Critical heat flux data set for boiling R-12 in uniformly heated vertical tubes under transient conditions.
The critical heat flux (CHF) phenomenon has been extensively investigated in the past with particular regard to steady-state nuclear reactor operating conditions, with the aim of establishing the bounds of the thermohydraulic design. However transient CHF...
G. P. Celata M. Cumo F. D'Annibale G. E. Farello
Effects of mass transfer on transient free convective flow past a semi-infinite vertical plate with constant heat flux
Implicit finite-difference method is employed to study the effects of the mass transfer on the transient free convection flow past a semiinfinite vertical plate in the presence of constant heat flux. The resulting algebraic equations are solved by Thomas algorithm. The transient velocity, temperature and concentration profiles, the average skin-friction, the Nusselt number and the Sherwood number are shown graphically. It is observed that an increase in the Schmidt number leads to a decrease in the average skin-friction and the average Sherwood number but an increase in the Nusselt number.
Soundalgekar, Vyenkatesh M.; Gokhale, Mukund Y.
Natural convection with surface radiation from a planar heat generating element mounted freely in a vertical channel
Experiments and numerical simulations have been conducted to study the conjugate heat transfer by natural convection and surface radiation from a planar heat generating element placed centrally between two adiabatic vertical plates. The relevant problem dependent parameters considered in this study are modified Rayleigh number, channel aspect ratio, stream-wise location of the heat generating element, and surface emissivities of the heat generating element and the adiabatic side plates. Experiments are conducted for different values of modified Rayleigh number ranging from 3.2 � 105 to 1.6 � 107 and surface emissivities 0.05, 0.55, 0.75 and 0.85. The interdependence between the heat transfer mechanism and the flow field under the influence of surface radiation on natural convection is explored and discussed. Experimental correlations for total and convective Nusselt number, and dimensionless temperature in terms of relevant parameters have been developed. The mathematical model governing the problem has been numerically solved using a commercial computational fluid dynamics package FLUENT 6.3 and the numerical predictions substantiate the experimental observations.
Rajkumar, M. R.; Venugopal, G.; Lal, S. Anil
Forced convective flow and heat transfer of upward cocurrent air-water slug flow in vertical plain and swirl tubes
This experimental study comparatively examined the two-phase flow structures, pressured drops and heat transfer performances for the cocurrent air-water slug flows in the vertical tubes with and without the spiky twisted tape insert. The two-phase flow structures in the plain and swirl tubes were imaged using the computerized high frame-rate videography with the Taylor bubble velocity measured. Superficial liquid Reynolds number (Re{sub L}) and air-to-water mass flow ratio (AW), which were respectively in the ranges of 4000-10000 and 0.003-0.02 were selected as the controlling parameters to specify the flow condition and derive the heat transfer correlations. Tube-wise averaged void fraction and Taylor bubble velocity were well correlated by the modified drift flux models for both plain and swirl tubes at the slug flow condition. A set of selected data obtained from the plain and swirl tubes was comparatively examined to highlight the impacts of the spiky twisted tape on the air-water interfacial structure and the pressure drop and heat transfer performances. Empirical heat transfer correlations that permitted the evaluation of individual and interdependent Re{sub L} and AW impacts on heat transfer in the developed flow regions of the plain and swirl tubes at the slug flow condition were derived. (author)
Chang, Shyy Woei [Thermal Fluids Laboratory, National Kaohsiung Marine University, No. 142, Haijhuan Road, Nanzih District, Kaohsiung City 81143 (China); Yang, Tsun Lirng [Department of Marine Engineering, National Kaohsiung Marine University, No. 142, Haijhuan Road, Nanzih District, Kaohsiung City 81143 (China)
Experimental study of a closed loop vertical ground source heat pump system
Ground source heat pumps (GSHPs), also known as geothermal heat pumps, are a promising new technology that has been used for the last three years in the Turkish market. The main objective of the present study, which was performed for the first time in Turkey at the university level, is to investigate the performance characteristics of a GSHP system with
Arif Hepbasli; Ozay Akdemir; Ebru Hancioglu
Natural convection in enclosures with floor cooling subjected to a heated vertical wall
Natural convection in enclosures is extensively investigated due to its importance in many applications, such as heat transfer through double glazing windows, electronic cooling devices, geophysical applications, etc. Two configurations that have been extensively explored in the literature are the differentially heated enclosures and the Rayleigh�Benard problems. In the present work, a different kind of problem is investigated, namely the
A. A. Mohamad; J. Sicard; R. Bennacer
Experimental investigation of in-line tube bundle heat transfer process to vertical downward foam flow
Usage of two phase flow as a coolant allows to reach more intensive heat transfer process. This paper presents the results of the investigation of the heat transfer between the in-line tube bundle and statically stable aqueous foam flow. The flow of the foam was generated at the top of the experimental channel and crossed down the tubes of the
J. Gylys; T. Zdankus; R. Jonynas; R. Maladauskas
Retrieved Vertical Profiles of Latent Heat Release Using TRMM Rainfall Products for February 1998
This paper represents the first attempt to use Tropical Rainfall Measuring Mission (TRMM) rainfall information to estimate the four-dimensional latent heating structure over the global Tropics for one month (February 1998). The mean latent heating profiles over six oceanic regions [Tropical Ocean and Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) Intensive Flux Array (IFA), central Pacific, South Pacific Convergence
W.-K. Tao; S. Lang; W. S. Olson; R. Meneghini; S. Yang; J. Simpson; C. Kummerow; E. Smith; J. Halverson
Study on effect of liquid level on the heat leak into vertical cryogenic vessels
The diminishing of heat leak into cryogenic vessels can prolong the storage time of cryogenic liquid. With the storage of cryogenic liquid reducing, the heat leak decreases, while the actual storage time increases. Compared with the theoretical analysis, the numerical simulation can more accurately calculate the heat transfer and temperature distribution in the vessel with complex structure. In this paper the steady state heat leak into cryogenic vessels with different liquid level height is analyzed using a finite element model. And liquid nitrogen boil-off method was adopted in experiments to validate the result of numerical simulation. Experimental results indicate favorable agreement with numerical simulation by ANSYS software. The effect of liquid level on heat leak into the cryogenic vessel can be considered in calculation of storage time and structure design.
Li, Yang; Wang, Rongshun; Wang, Caili
Detecting hidden volcanic explosions from Mt. Cleveland Volcano, Alaska with infrasound and ground-coupled airwaves
In Alaska, where many active volcanoes exist without ground-based instrumentation, the use of techniques suitable for distant monitoring is pivotal. In this study we report regional-scale seismic and infrasound observations of volcanic activity at Mt. Cleveland between December 2011 and August 2012. During this period, twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent, and ground-coupled acoustic waves were recorded at seismic stations across the Aleutian Arc. Several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data. However, many explosions eluded initial, automated, analyses of satellite data due to poor weather conditions. Infrasound and seismic monitoring provided effective means for detecting these hidden events. We present results from the implementation of automatic infrasound and seismo-acoustic eruption detection algorithms, and review the challenges of real-time volcano monitoring operations in remote regions. We also model acoustic propagation in the Northern Pacific, showing how tropospheric ducting effects allow infrasound to travel long distances across the Aleutian Arc. The successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the Aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.
De Angelis, Silvio; Fee, David; Haney, Matthew; Schneider, David
Vertical Mass, Momentum, Moisture, and Heat Fluxes in Hurricanes above 10 km during CAMEX-3 and CAMEX-4
The third and fourth NASA Convection and Moisture Experiments (CAMEX-3 and CAMEX-4) during the Atlantic hurricane seasons of 1998 and 2001, respectively, have yielded comprehensive multi-aircraft datasets using, both remote and in-situ instrumentation. Among these are high-frequency in-situ measurements of vertical wind, horizontal wind, temperature, and water vapor, made from NASA's DC-8 aircraft in the upper portions of the hurricane (typically above 10 km). Wind and temperature measurements were made at 20 hz by the NASA/Ames Meteorological Measurement System, while water vapor was measured at 1 hz by the NASA/JPL Laser Hygrometer. Fluxes of heat, momentum, and moisture at these levels are important, since modeling studies have shown that ice processes, which are dominant at temperatures below -40C (where the DC-8 flies) are important for hurricane intensification. Also, there are indications from satellite studies that latent heat release at DC-8 levels is significant, perhaps a third of those in the mid-troposphere. Preliminary results show that typical updrafts in the eyewall region are comparable to or higher than previous observations of tropical convection, with several instances of updraft magnitudes of 15 meters per second (the maximum observed was 21 meters per second). They also show significant supersaturations (10-20% or more) in the updrafts, which would enhance the latent heat release at the upper levels of the hurricane. This paper will examine the magnitude and distribution of small and mesoscale vertical fluxes of mass, momentum, moisture, and heat. The goal is to examine the role of these fluxes in the overall budgets of the respective quantities in the upper portions of the hurricane.
Pfister, Leonhard; Bui, Paul; Herman, Robert; Dean-Day, Jon; Hipskind, R. Stephen (Technical Monitor)
Geothermal Studies of the Outokumpu Deep Drill Hole, Finland: Vertical variation in heat flow and palaeoclimatic implications
Detailed geothermal studies of deep drill holes provide insights to heat transfer processes in the crust, and allow separation of different factors involved, such as palaeoclimatic and structural conductive effects as well as advective fluid flow effects. We present high resolution geothermal results of the 2,516 m deep Outokumpu Deep Drill Hole in eastern Finland drilled in 2004-2005 into a Palaeoproterozoic formation with metasedimentary rocks, ophiolite-derived altered ultramafic rocks and pegmatitic granite. The down-hole temperatures have been logged five times after end of drilling and extend to day 948 after drilling. The hole is completely cored (79% core coverage) and thermal conductivity measurements were done at 1 m intervals. The geothermal results on temperature gradient, thermal conductivity and heat flow density yield an exceptionally detailed data set and indicate a significant vertical variation in gradient and heat flow density. Heat flow density increases from about 28-32 mW m-2 in the uppermost 1000 m to 40-45 mW m-2 at depths exceeding 2000 m. The estimated undisturbed surface heat flow value is 42 mWm-2. We present results on forward and inverse transient conductive models which suggest that the vertical variation in heat flow can mostly be attributed to a palaeoclimatic effect due to ground surface temperature (GST) variations during the last 100,000 years. The modelling suggests that the average GST was about -3�-4�C during the Weichselian glaciation. Holocene GST values are within �2 degree from the present average GST in Outokumpu (5�C). The topographic hydraulic heads and hydraulic conductivity of crystalline rocks are low which suggests that advective heat transfer in the formation is not significant. The slow replacement of fresh flushing water by saline formation fluids is observed in the hole, but it does not generate significant thermal disturbances in the logs. On the other hand, free sluggish thermal convection is present in the large diameter (22 cm) borehole, and temperature variations in the range of few mK to 0.01 K occur over times of minutes to tens of minutes. Theory suggests that convection cells are about as tall as the drill hole diameter, and thus the free convection is expected to generate only local thermal 'noise'not affecting the general geothermal results. Reference: Physics of the Earth and Planetary Interiors 188 (2011) 9-25 (doi:10.1016/j.pepi.2011.06.002)
Kukkonen, I. T.; Rath, V.; Kivek�s, L.; �afanda, J.; ?ermak, V.
Geothermal studies of the Outokumpu Deep Drill Hole, Finland: Vertical variation in heat flow and palaeoclimatic implications
Detailed geothermal studies of deep drill holes provide insights to heat transfer processes in the crust, and allow separation of different factors involved, such as palaeoclimatic and structural conductive effects as well as advective fluid flow effects. We present high resolution geothermal results of the 2516 m deep Outokumpu Deep Drill Hole in eastern Finland drilled in 2004-2005 into a Palaeoproterozoic formation with metasedimentary rocks, ophiolite-derived altered ultramafic rocks and pegmatitic granite. The down-hole temperatures have been logged five times after end of drilling and extend to day 948 after drilling. The hole is completely cored (79% core coverage) and thermal conductivity measurements were done at 1 m intervals. The geothermal results on temperature gradient, thermal conductivity and heat flow density yield an exceptionally detailed data set and indicate a significant vertical variation in gradient and heat flow density. Heat flow density increases from about 28 - 32 mW m -2 in the uppermost 1000 m to 40-45 mW m -2 at depths exceeding 2000 m. The estimated undisturbed surface heat flow value is 42 mW m -2. We present results on forward and inverse transient conductive models which suggest that the vertical variation in heat flow can mostly be attributed to a palaeoclimatic effect due to ground surface temperature (GST) variations during the last 100,000 years. The modeling suggests that the average GST was about -3 to -4 �C during the Weichselian glaciation. Holocene GST values are within �2� from the present average GST in Outokumpu (5 �C). The topographic hydraulic heads and hydraulic conductivity of crystalline rocks are low which suggests that advective heat transfer in the formation is not significant. The slow replacement of fresh flushing water by saline formation fluids is observed in the hole, but it does not generate significant thermal disturbances in the logs. On the other hand, free sluggish thermal convection is present in the large diameter (22 cm) borehole, and temperature variations in the range of few mK to 0.01 K occur over times of minutes to tens of minutes. Theory suggests that convection cells are about as tall as the drill hole diameter, and thus the free convection is expected to generate only local thermal 'noise' not affecting the general geothermal results.
Kukkonen, Ilmo T.; Rath, Volker; Kivek�s, Liisa; �afanda, Jan; ?ermak, Vladimir
The Effect of a Transverse Notch on the Heat Transfer Rate from a Heated Vertical Plate in Free Convection.
Based on the results of this study, the following conclusions are drawn: (1) The notch effect on heat transfer is local in nature with the range of influence restricted to a region from about one inch below the notch to about two inches above the notch. (...
C. C. Fletcher
Investigation on the effect of filling ratio on the steady-state heat transfer performance of a vertical two-phase closed thermosyphon
Filling ratio of the working fluid has a predominant effect on the heat transfer characteristics of a two-phase closed thermosyphon (TPCT). A comprehensive model is developed to investigate the effect of filling ratio on the steady-state heat transfer performance of a vertical TPCT. Three types of flow pattern and two types of transition, according to the distribution of liquid film
B. Jiao; L. M. Qiu; X. B. Zhang; Y. Zhang
Numerical modelling of temperature fields in the flow boiling liquid through a vertical minichannel with an enhanced heating surface
The paper presents results of heat transfer research on flow boiling in a rectangular minichannel positioned vertically, with an enhanced surface. One of the channel walls was made of thin foil powered by direct current. This foil is enhanced on the side contacting fluid in the minichannel. It is possible to observe both surfaces of the minichannel through two openings covered with glass panes. One allows detecting temperature of the plain side of the foil by liquid crystal thermography. The opposite surface of the minichannel (from the enhanced side of the foil) can be observed through the other glass pane. The observations of the flow structures allowed to calculate the void fraction for some cross-sections of selected two phase flow images. In mathematical modelling of the considered process stationary heat transfer in a glass pane, heating foil and boiling liquid can be described with Laplace equation, Poisson equation and energy equation, respectively. For completeness of the model a corresponding system of boundary conditions was given. The two-dimensional temperature fields of glass pane, heating foil and fluid was computed with the Trefftz method. The equalizing calculus used to smooth the measured data has reduced errors.
Ho?ejowska, Sylwia; Piasecka, Magdalena
Interaction of surface radiation with conjugate mixed convection from a vertical channel with multiple discrete heat sources
Important results of a numerical study performed on combined conduction-mixed convection-surface radiation from a vertical channel equipped with three identical flush-mounted discrete heat sources in its left wall are provided here. The channel has walls of identical height with the spacing varied by varying its aspect ratio (AR). The cooling medium is air that is considered to be radiatively transparent. The heat generated in the channel gets conducted along its walls before getting dissipated by mixed convection and radiation. The governing equations for fluid flow and heat transfer are considered without boundary layer approximations and are transformed into vorticity-stream function form and are later normalized. The resulting equations are solved, along with relevant boundary conditions, making use of the finite volume method. The computer code written for the purpose is validated both for fluid flow and heat transfer results with those available in the literature. Detailed parametric studies have been performed and the effects of modified Richardson number, surface emissivity, thermal conductivity and AR on various pertinent results have been looked into. The significance of radiation in various regimes of mixed convection has been elucidated. The relative contributions of mixed convection and radiation in carrying the mandated cooling load have been thoroughly explored.
Londhe, Shrikant D.; Gururaja Rao, C.
Study on heat transfer characteristic of ethanol-water mixture condensation on a vertical micro-tube
In present experiment, the vapor mixture with different velocities (2m.s-1, 4m.s-1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.16kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW.m-2.K1, which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from -20% to 20%.
Chen, Xiping; Wang, Jinshi; Qin, Junchao; Chong, Daotong; Yan, Junjie
MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect
A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory.
Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.
MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.
A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295
Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md
Effect of varying the depth of heat application on the adaptability of gutta-percha during warm vertical compaction.
The purpose of this study was to compare the adaptability of gutta-percha after varying the depth of heat application in the obturation of a set of standard root canals. A split-tooth model was constructed using a human maxillary central incisor. The root canal was cleaned and shaped using a step-back preparation to a size #60 FlexOFile at the working length (WL). Five shallow depressions were produced on the root canal wall. Twenty obturations without sealer were performed for each technique (thermoplasticized injectable (TI), lateral condensation, and warm vertical compaction (WVC) with heat applications at 3, 4, 5, and 7 mm from the WL). After each obturation the model was separated and the mesial and distal sides of each obturation were examined and videotaped at x 32 magnification. The quality of the obturation was graded based on the replication to the WL, replication of the artificial depressions, surface adaptation, and homogenicity of the gutta-percha. The Kruskal-Wallis analysis and the Student-Newman-Keuls tests indicated that all the techniques were significantly different from each other (p < 0.05) except for the TI group versus the WVC group with the heat application to within 3 mm from the WL (p > 0.05). The TI technique was ranked best followed by the WVC with heat applications at 3, 4, 5, and 7 mm. The lateral condensation technique received the lowest ranking. PMID:11469298
Smith, R S; Weller, R N; Loushine, R J; Kimbrough, W F
Rationale and technique for vertical compaction of warm gutta-percha: the heat wave approach.
Endodontic treatment rationale is based on anatomic principles, which state that all involved teeth can be saved if the root canal system is sealed, either nonsurgically or surgically, and the tooth is periodontally healthy or can be brought to health. Additionally, the tooth must be restorable, and the patient must be immunologically competent. The history of endodontics validates the effort to clean, shape, and obturate the root canal system as prerequisites for preventing and resolving lesions of endodontic origin. The vertical compaction of warm gutta-percha HW is a time-tested and effective method to achieve predictably successful outcomes. PMID:17955861
West, John
Critical heat-flux experiments under low-flow conditions in a vertical annulus
An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF.
Mishima, K.; Ishii, M.
Improved Detection of Vulcanian Explosions from Mt. Cleveland, Alaska with Infrasound and Ground-Coupled Airwaves
Geophysical measurements play a crucial role in detecting, tracking, and interpreting unrest at active volcanoes. Although large explosions with Volcanic Explosivity Index (VEI) of 4 or greater have been observed in seismic records at long range, smaller eruptions, with VEI less than 3, are unlikely to be detected seismically more than a few kilometers away from the source. In the Aleutian Islands, where several active volcanoes exist without ground-based instrumentation, infrasound has proven to be a particularly sensitive and reliable tool for the detection of remote volcanic explosions. We report on recent activity at Mt. Cleveland, a stratovolcano situated on western half of Chuginadak Island, Alaska. Between December 25, 2011 and August 7, 2012, we detected nineteen explosive events from Cleveland using an infrasound array located 1000 km away in Dillingham, Alaska and ground-coupled airwaves recorded on regional seismic stations at distances of 80-500 km. Many of the detected explosions have resulted from the presumed destruction of small lava domes within the summit crater. We have implemented automatic detection algorithms at the Alaska Volcano Observatory on data streams from both the infrasound array and seismic stations to dispatch warnings of explosive activity at Mt. Cleveland. The main challenge to near-real-time (< 10 minutes) detection has been the propagation time (50 minutes) needed for acoustic waves to travel 1000 km to the infrasound array. With recently installed infrasound arrays at nearby Okmok (150 km) and Akutan (300 km) volcanoes, this issue will become less of a problem in the future since the travel times from Cleveland to Okmok and Akutan are 6 and 15 minutes, respectively. Additionally, these closer arrays will allow better estimation of source parameters and inferences on vulcanian eruptions from Mt. Cleveland. Several of the explosions over the past year eluded detection by routine satellite remote sensing checks due to generally poor weather conditions and thick cloud cover in the Aleutian Islands. Thus, infrasound monitoring provides a highly sensitive means for detecting "hidden" volcanic explosions, with plumes obscured by clouds that would otherwise have gone undetected. The catalog of 19 explosive events over the first 8 months of infrasound monitoring has provided new insights into the activity at Mt. Cleveland; for example, no previous 8-month period have as many as 19 explosions been detected. Thus, Mt. Cleveland is considerably more active, in terms of volcanic explosions, than previously known. Furthermore, this repeating source of infrasound has revealed new information about acoustic propagation in the Northern Pacific. During the winter months, propagation in the Northeast direction is enhanced by a strong tropospheric duct filling an otherwise expected acoustic shadow zone, and allowing infrasound and ground-coupled airwaves to be recorded approximately 120 km away from the source. Overall, the successful results from Mt. Cleveland provide motivation for expanded efforts in infrasound monitoring across the Aleutian Arc in addition to improved knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.
De Angelis, S.; Fee, D.; Haney, M. M.; Schneider, D. A.
Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube
The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m\\/s), the inlet subcoolings (DeltaTsub,in=48.6 to 154.7 K), the inlet pressure (Pin=735.2 to 969.0 kPa) and the increasing heat input (Q0 exp(t\\/tau), tau=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of
Critical Heat Fluxes of Subcooled Water Flow Boiling against Inlet Subcooling in Short Vertical Tube
The critical heat fluxes (CHFs) of subcooled water flow boiling for the test tube inner diameters (d=3 and 6mm) and the heated lengths (L=67, 120 and 150mm) are systematically measured for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, in=48 to 148K), the outlet subcoolings (DeltaTsub, out=10.5 to 95.1K), the inlet pressure (Pin=753 to 995kPa) and the outlet
Koichi Hata; Hirokazu Komori; Masahiro Shiotsu; Nobuaki Noda
Determining Vertical Groundwater-Surface Water Exchange Using a New Approach to Solve the 1D Heat Transport Equation
In water management it has become common practice to consider groundwater and surface water as coupled parts of the same system. This has led to intensive research into groundwater-surface water interactions. Part of that research is being conducted with the aim to improve delineation and quantification of groundwater-surface water exchange fluxes or vertical Darcy velocities using heat as a natural tracer. In these cases, streambed temperatures can be measured at various depths within the streambed using e.g. multilevel temperature probes. Together with additional information such as hydraulic head, temperature data can then be incorporated into numerical models, which in turn can be used to make sound assumptions on water flow in the hyporheic zone as well as to estimate hydraulic conductivity within the streambed. As these models are usually complex and data intensive, procedures have been developed that allow for a fast assessment of the vertical exchange flow component based on the 1D heat transport equation for a semi-infinite half-space. So far, most of these 1D solutions make use of the sinusoidal components of the diurnal temperature fluctuations between different depths within the streambed. However, they are limited regarding their use of data in the frequency domain as well as their ability to conduct proper uncertainty assessment. The authors propose a solution for the 1D case based on the determination of the frequency response function between the input temperature at a point z0 and the temperature at a position z for a given vector containing information regarding thermal and hydraulic parameters as well as sediment properties. This frequency response function and its uncertainty are obtained by using the Local Polynomial Method, a method that uses information regarding the randomness of the input data and the spectral smoothness. With the frequency response function and its uncertainty a maximum-likelihood estimator based on non-linear least-squares optimization techniques is then used to determine model quality, estimate model parameters and determine their uncertainty. Optimized parameters are then back-transformed from the frequency domain to the time domain where they hold information regarding the vertical exchange fluxes as well as thermal parameters. The methodology was verified using streambed temperature data obtained from multiple locations within a reach of the Slootbeek, a small sidearm of the River Aa in Belgium. It allowed for a reliable quantification of the vertical exchange flux component and its uncertainty and results could be obtained faster as compared to other 1D methods.
Schneidewind, U.; Anibas, C.; Vandersteen, G.; Batelaan, O.; Joris, I.; Seuntjens, P.; Voloshchenko, O.
Gas Evaporation of Zn by Means of the Top-Heating Vertical Furnace
Gas evaporation of Zn without convection was carried out in the top-heating furnace. The temperature distribution and the pressure of He gas in the furnace were controlled and the particles deposited at various places of temperature in the furnace were observed by scanning electron microscope. The conditions of nucleation and growth mechanisms of the evaporated Zn vapors were discussed.
Dohi, Minoru; Sawai, Shinya; Kato, Manabu; Wada, Nobuhiko
Critical Heat Fluxes to Water in a Vertical Annulus in a Natural Circulation System.
The influences of sub-cooling and pressure on the values of the critical heat flux in a natural circulation system were investigated. The system used could simulate an experimental loop in a nuclear reactor in case of failure of forced circulation cooling...
M. Vaxman
Effects of heat and mass transfer in flow along a vertical stretching cylinder with slip conditions
This article explores the magnetohydrodynamic (MHD) axisymmetric flow by a stretching cylinder with slip conditions. Simultaneous effects of heat and mass transfer are considered. The relevant equations are computed. Impact of various parameters on the velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number is discussed.
Hayat, T.; Qayyum, A.; Alsaedi, A.
Heat and mass transfer in MHD free convection from a moving permeable vertical surface by a perturbation technique
Numerical results are presented for heat and mass transfer effect on hydromagnetic flow of a moving permeable vertical surface. An analysis is performed to study the momentum, heat and mass transfer characteristics of MHD natural convection flow over a moving permeable surface. The surface is maintained at linear temperature and concentration variations. The non-linear coupled boundary layer equations were transformed and the resulting ordinary differential equations were solved by perturbation technique [Aziz A, Na TY. Perturbation methods in heat transfer. Berlin: Springer-Verlag; 1984. p. 1-184; Kennet Cramer R, Shih-I Pai. Magneto fluid dynamics for engineers and applied physicists 1973;166-7]. The solution is found to be dependent on several governing parameter, including the magnetic field strength parameter, Prandtl number, Schmidt number, buoyancy ratio and suction/blowing parameter, a parametric study of all the governing parameters is carried out and representative results are illustrated to reveal a typical tendency of the solutions. Numerical results for the dimensionless velocity profiles, the temperature profiles, the concentration profiles, the local friction coefficient and the local Nusselt number are presented for various combinations of parameters.
Abdelkhalek, M. M.
Heat transfer simulation in a vertical Bridgman CdTe growth configuration
Modelling and numerical simulation of crystal growth processes have been shown to be powerful tools in order to understand the physical effects of different parameters on the growth conditions. In this study a finite difference/control volume technique for the study of heat transfer has been employed. This model takes into account the whole system: furnace temperature profile, air gap between furnace walls and ampoule, ampoule geometry, crucible coating if any, solid and liquid CdTe thermal properties, conduction, convection and radiation of heat and phase change. We have used the commercial code FLUENT for the numerical resolution that can be running on a personal computer. Results show that the temperature field is very sensitive to the charge and ampoule peculiarities. As a consequence, significant differences between the velocity of the ampoule and that of the isotherm determining the solid/liquid interface have been found at the onset of the growth.
Martinez-Tomas, C.; Mu�oz, V.; Triboulet, R.
Non-equilibrium pressure control of the height of a large-scale, ground-coupled, rotating fluid column
When a ground-coupled, rotating fluid column is modeled incorporating non-equilibrium pressure forces in the Navier-Stokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infinite-height, classical solution, the non-equilibrium pressure solution yields a ground-coupled rotating fluid column of finite height. A viscous, non-equilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and non-equilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from the outer potential vortex region. Thus, the non-equilibrium region acts to confine and shield the central, rigid-body-like, rotating fluid core, justifying this examination of how such a rotating fluid column can interact with the ground. The resulting non-equilibrium ground-coupled, rotating fluid column solution was employed to estimate the central column heights of three well-documented dust devils, and the central column height predictions were consistent with published dust devil height statistics.
Ash, R. L.; Zardadkhan, I. R.
Vertical structure of convective heating over the large-scale subsidence region in the CMIP3 models
Vertical structure of tropical heating associated with convective activities is known to play an important role in determining a large-scale circulation (Hartmann et al. 1984; Wu 2003). Takayabu et al. (AGU2008) showed heating over the large-scale subsidence region is suppressed in the lower troposphere using TRMM data. They suggested a dry layer in the lower troposphere is important for the suppression of deep convection. In this study, apparent heat source (Q1) associated with convective activities in 22 20C3M model runs from the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset is analyzed over the subsidence region (monthly dp/dt > 0) in September-November seasons of 1979-2000. A multi-model ensemble average of Q1-QR, where radiative heating (QR) is obtained from JRA reanalysis data, well reproduces the suppressed heating profile over the subsidence region as observed by TRMM. Then we examine the impact of the lower-level dry layer to the strength of the suppression represented by a ratio of Q1-QR at 500hPa and 850hPa (Q1-QR500/850). Each model shows a decrease of Q1-QR500/850 as the relative humidity at 600hPa (RH600) decreases in the region RH600 < 35%. This relationship is identified in most of the models, JRA, and ERA reanalysis data, which means in each model, the dryness of the lower troposphere suppresses the deep convection effectively. Although most of the models reproduce the suppressed structure of the heating and its relationship with RH600, the strength of the suppression varies largely among the models. We speculate that the large diversity among models is influenced by cumulus parameterization schemes. When we compare six models with a similar parameterization scheme based on Arakawa and Schubert (1974), we find relatively converged relationships between RH600 and the suppression of deep convection. We will further discuss the scheme dependency at the poster. This study is financially supported by the Global Environment Research Fund (S-5-2) of the Ministry of the Environment, Japan.
Hirota, N.; Takayabu, Y. N.
Numerical investigation of heat and mass transfer during vertical Bridgman crystal growth under rotational vibrations
The paper deals with the numerical investigation of convective flows and heat and mass transfer in the directional solidification of binary melts in the presence of rotational vibrations of finite amplitude and frequency. The study is performed in the framework of the Boussinesq approximation and unsteady axisymmetric approach, taking into account the existence of the two-phase zone. The simulation is conducted for binary melt with low phase change temperature (succinonitrile with ethanol), using ANSYS Fluent package which realizes the finite volume method. The data on the temporal evolution of velocity, temperature and solute concentration fields in the melt and on the solute distribution in the grown crystal with and without vibrations are obtained. It is demonstrated that the vibrations make strong stabilizing effect; they reduce the radial segregation and prevent the pit formation and solidification front breakdown, which leads to a substantial increase of grown crystal homogeneity.
Lyubimova, T. P.; Parshakova, Ya. N.
Particle image velocimetry measurements for opposing flow in a vertical channel with a differential and asymmetric heating condition
Particle image velocimetry (PIV) measurements were carried out in an experimental investigation of laminar mixed convection in a vertical duct with a square cross-section. The main downward water-flow is driven by gravity while a portion of a lateral side is heated, and buoyancy forces produce non-stationary vortex structures close to the heated region. Various ranges of the Grashof number, Gr are studied in combination with the Reynolds number, Re varying from 300 to 700. The values of the generalized buoyancy parameter or Richardson number, Ri = Gr/Re{sup 2} parallel to the Grashof number are included in the results. The influence of these nondimensional parameters and how they affect the fluid flow structure and vortex sizes and locations are reported. The flow patterns are nonsymmetric, periodic, and exhibit increasing complexity and frequency for increasing buoyancy. For the averaged values of the resulting vortex dimensions, it was found that a better and more congruent representation occurs when employing the Grashof and Reynolds numbers as independent parameters. (author)
Martinez-Suastegui, L. [Graduate Student, Facultad de Ingenieria, Universidad Nacional Autonoma de Mexico, C.U., Mexico 04510 D.F. (Mexico); Trevino, C. [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, C.U., Mexico 04510 D.F. (Mexico)
New data on two-phase two-component heat transfer and hydrodynamics in a vertical tube
In forced-convective two-phase, two component (gas-liquid) flow, experimental data for mean heat-transfer coefficients, pressure drop and flow patterns were taken simultaneously for the flow in a 1.17-cm i.d. electrically heated vertical tube using three liquids: water, glycerine and water and silicone liquid with air as the gas phase. The combination of silicone liquid and the glycerine and water solution provided a set of data in which the surface tension changed by a factor of 3.4 (being lower for the silicone liquid) with a rough matching of other hydrodynamic properties and a precise matching of the Prandtl number (63 at 25 C). The flow-pattern results showed a significant change in the bubble-slug boundary for the silicone liquid compared with the glycerine and water solution, while the pressure drop results for silicone-air, in the range of V(SL) between 0.277 and 0.690 m/s at high V(SC) showed a sudden drop in Delta/P(tot) followed by a subsequent increase.
Rezkallah, K. S.; Sims, G. E.
Effect of viscous dissipation on an MHD free convective flow past a semi-infinite vertical cone with a variable surface heat flux
An analysis is presented to investigate the influence of viscous dissipation on a free convection flow over a vertical cone with a variable surface heat flux under the action of a transverse magnetic field. The heat transfer characteristics of the free convection flow are investigated numerically. Numerical solutions for transformed governing equations with a variable surface heat flux are obtained. Velocity, temperature, local shear stress, and heat transfer coefficients are calculated for various values of the problem parameters and presented in the graphical form. The effects of the magnetic parameter, the dissipation number, the power-law index, the angle between the cone generatrix and the vertical line, and the Prandtl number on the flow are discussed. For validation of the present numerical results, they are compared with available experimental data and are found to agree well.
Palani, G.; Ragavan, A. R.; Thandapani, E.
Heat transfer, pressure drop and void fraction in two- phase, two-component flow in a vertical tube
There are very few data existing in two-phase, two- component flow where heat transfer, pressure drop and void fraction have all been measured under the same conditions. Such data are very valuable for two-phase heat-transfer model development and for testing existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction. An experiment was performed which adds markedly to the available data of the type described in terms of the range of gas and liquid flow rates and liquid Prandtl number. Heat transfer and pressure drop measurements were taken in a vertical 11.68-mm i.d. tube for two-phase (gas-liquid) flows covering a wide range of conditions. Mean void fraction measurements were taken, using quick- closing valves, in a 12.7-mm i.d. tube matching very closely pressures, temperatures, gas-phase superficial velocities and liquid-phase superficial velocities to those used in the heat-transfer and pressure-drop experiments. The gas phase was air while water and two aqueous solutions of glycerine (59 and 82% by mass) were used as the liquid phase. In the two-phase experiments the liquid Prandtl number varied from 6 to 766, the superficial liquid velocity from 0.05 to 8.5 m/s, and the superficial gas velocity from 0.02 to 119 m/s. The measured two-phase heat-transfer coefficients varied by a factor of approximately 1000, the two-phase frictional pressure drop ranged from small negative values (in slug flow) to 93 kPa and the void fraction ranged from 0.01 to 0.99; the flow patterns observed included bubble, slug, churn, annular, froth, the various transitions and annular-mist. Existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction were: tested against the present data for mean heat-transfer coefficients. It was found that the methods with more restrictions (in terms of the applicable range of void fraction, liquid Prandtl number or liquid superficial Reynolds number) give better predictions. Among the most restrictive methods, the method of Drucker et al. is recommended. A method less restrictive, but still giving good predictions, is the Liquid Acceleration Model for superficial liquid Reynolds numbers greater than 2000. For local heat-transfer coefficients, a method proposed by Vijay, where Spalding's single-phase boundary-layer theory was adapted to the two-phase case, was tested considering the flow patterns individually and various methods of calculating two-phase properties. Good predictions were obtained for the case of bubble and froth flows when liquid properties were used as the two- phase mixture properties.
Sujumnong, Manit
A vertical heat pipe: an experimental and statistical study of the thermal performance in the presence of low-frequency vibrations
New experimental results present the effects of low-frequency vibrations in a vertical heat pipe. The thermal resistance was investigated under different heat transfer rates, filling ratios and frequencies, increase of which improved the thermal performance. The vibrations were effective 33.83 % on the performance, and the best performance was estimated using the L16 array of Taguchi method, and it was achieved with the thermal resistance 0.064 K/W in the frequency 30 Hz.
Alaei, Amir; Kafshgari, Morteza Hasanzadeh; Rahimi, Shahab Kashani
The characteristics and visualization of critical heat flux of R-134a flowing in a vertical annular geometry with spacer grids
In the present paper, critical heat flux (CHF) experiments of forced convection boiling were performed to investigate the CHF characteristics of a vertical annular channel with one heated rod and four spacer grids for new refrigerant R-134a. The experiments were conducted under outlet pressure of 11.6, 13, 16 and 20bar, mass fluxes of 100�600kg\\/m2s, and inlet temperatures of 25�40�C. The
Kwi Lim Lee; In Cheol Bang; Soon Heung Chang
Characterizing fractured rock aquifers using heated Distributed Fiber-Optic Temperature Sensing to determine borehole vertical flow
In highly heterogeneous media, fracture network connectivity and hydraulic properties can be estimated using methods such as packer- or cross-borehole pumping-tests. Typically, measurements of hydraulic head or vertical flow in such tests are made either at a single location over time, or at a series of depths by installing a number of packers or raising or lowering a probe. We show how this often encountered monitoring problem, with current solutions sacrificing either one of temporal or spatial information, can be addressed using Distributed Temperature Sensing (DTS). Here, we electrically heat the conductive cladding materials of cables deployed in boreholes to determine the vertical flow profile. We present results from heated fiber optic cables deployed in three boreholes in a fractured rock aquifer at the much studied experimental site near Ploemeur, France, allowing detailed comparisons with alternative methods (e.g. Le Borgne et al., 2007). When submerged in water and electrically heated, the cable very rapidly reaches a steady state temperature (less than 60 seconds). The steady state temperature of the heated cable, measured using the DTS method, is then a function of the velocity of the fluid in the borehole. We find that such cables are sensitive to a wide range of fluid velocities, and thus suitable for measuring both ambient and pumped flow profiles at the Ploemeur site. The cables are then used to monitor the flow profiles during all possible configurations of: ambient flow, cross-borehole- (pumping one borehole, and observing in another), and dipole-tests (pumping one borehole, re-injection in another). Such flow data acquired using DTS may then be used for tomographic flow inversions, for instance using the approach developed by Klepikova et al., (submitted). Using the heated fiber optic method, we are able to observe the flow response during such tests in high spatial detail, and are also able to capture temporal flow dynamics occurring at the start of both the pumping and recovery phase of cross-borehole- and dipole- tests. In addition, the clear advantage of this is that by deploying a single fiber optic cable in multiple boreholes at a site, the flow profiles in all boreholes can be simultaneously measured, allowing many different pumping experiments to be conducted and monitored in a time efficient manner. Klepikova M. V., Le Borgne T., Bour O., and J-R.de Dreuzy, Inverse modelling of flow tomography experiments in fractured media, submitted to Water Resources Research. Le Borgne T., Bour O., Riley M. S., Gouze P., Pezard P.A., Belghoul A., Lods G., Le Provost R., Greswell R. B., Ellis P.A., Isakov E., and B. J. Last, Comparison of alternative methodologies for identifying and characterizing preferential flow paths in heterogeneous aquifers. Journal of Hydrology 2007, 345, 134-148.
Read, T. O.; Bour, O.; Selker, J. S.; Le Borgne, T.; Bense, V.; Hochreutener, R.; Lavenant, N.
Unsteady mass transfer in mixed convective heat flow from a vertical plate embedded in a liquid-saturated porous medium with melting effect
This paper numerically studies the transient mass transfer in mixed convective heat flow with melting effect from a vertical plate in a liquid saturated porous medium in the presence of aiding external flow. The governing equations are transformed into the non-dimensional form by using pseudo similarity coordinate (?) and dimensionless time (?). The resulting two dimensional boundary value problem (BVP)
W. T. Cheng; C. H. Lin
Non-Darcy unsteady mixed convection flow near the stagnation point on a heated vertical surface embedded in a porous medium with thermal radiation and variable viscosity
The unsteady mixed convection boundary layer flow near the stagnation point on a heated vertical plate embedded in a fluid saturated porous medium is studied. It is assumed that the unsteadiness is caused by the impulsive motion of the free stream velocity and by sudden increase in the surface temperature. Both the buoyancy assisting and the buoyancy opposing flow situations
I. A. Hassanien; T. H. Al-Arabi
Heat transfer and flow behaviour of aqueous suspensions of TiO 2 nanoparticles (nanofluids) flowing upward through a vertical pipe
Stable aqueous TiO2 nanofluids with different particle (agglomerate) sizes and concentrations are formulated and measured for their static thermal conductivity and rheological behaviour. The nanofluids are then measured for their heat transfer and flow behaviour upon flowing upward through a vertical pipe in both the laminar and turbulent flow regimes. Addition of nanoparticles into the base liquid enhances the thermal
Yurong He; Yi Jin; Haisheng Chen; Yulong Ding; Daqiang Cang; Huilin Lu
Ground Coupling and Single-Blow Thermal Storage in a Double-Envelope House.
The possibility of ground thermal storage and coupling in a double-shell house is investigated. Temperature distribution in the ground, utilizing measured ground temperatures, is obtained, and the amount of heat retrieval is assessed. One experimental mod...
H. T. Ghaffari R. F. Jones
Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube
Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1,500t.h-1 and the heat flux on test tubes ranges from 10 to 40 kW.m-2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8~5.7 times of that in smooth tube and the pressure drop of the porous surface tube is 0.99~1.007 times of that in the smooth tube. The physical mechanisms of the enhanced heat transfer characteristics of flow boiling in the porous surface tube are analyzed. By the regression analysis of the experimental data, correlations predicting the flow boiling heat transfer coefficient and pressure drop of glycol-water solution within the error range of +/-20% are established. The experimental results can be used to guide the design of heat exchange equipment using the porous surface tube as heat transfer elements under these test conditions.
Qiao, Shouxu; Wang, Haijun; Gu, Hongfang; Luo, Yushan; Zhang, Lei; Xiong, Wei
Solar energy and heat pumps: evaluation of combined systems for heating and cooling of buildings
An analysis of a broad range of solar assisted heat pump systems was carried out. Systems were divided into three categories on the basis of whether ground coupling was included in the system and, if so, whether solar energy was stored in the ground or used in some other way. In the category of non-ground-coupled systems, an advanced air-source heat
J. W. Andrews; M. A. Catan; P. Le Doux
Ground coupling and single-blow thermal storage in a double-envelope house
The possibility of ground thermal storage and coupling in a double shell house was investigated. Temperature distribution in the ground, utilization of measured ground temperatures, and the amount of heat retrieval are assessed. One experimental model and several hypothetical models are introduced, and their affects and advantages are compared.
H. T. Ghaffari; R. F. Jones
Ghaffari, H. T.; Jones, R. F.
Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones
Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m�), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufri�re volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.
Gaudin, Damien; Finizola, Anthony; Beauducel, Fran�ois; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline
An experimental study on the critical heat flux for low flow of water in a non-uniformly heated vertical rod bundle over a wide range of pressure conditions
An experimental study of the critical heat flux (CHF) has been performed for a water flow in a non-uniformly heated vertical 3�3 rod bundle under low flow and a wide range of pressure conditions. The experiment was especially focused on the parametric trends of the CHF and the applicability of the conventional CHF correlations to a return-to-power conditions of a
Sang-Ki Moon; Se-Young Chun; Seok Cho; Won-Pil Baek
Experimental investigation on heat transfer of forced convection condensation of ethanol-water vapor mixtures on a vertical mini-tube
In this paper, condensation heat transfer characteristics of ethanol-water vapor mixtures on a vertical mini-vertical tube with 1.221 mm outside diameter were investigated experimentally. The experiments were performed at different velocities and pressures over a wide range of ethanol mass fractions in vapor. The test results indicated that, with respect to the change of the vapor-to-surface temperature difference, the condensation curves of the heat transfer coefficients revealed nonlinear characteristics, and had peak values. At 2 % ethanol mass fraction in vapor, the condensation heat transfer coefficient value of the ethanol-water vapor mixture was found to have a maximum heat transfer coefficient of 50 kW m-2 K-1, which was 3-4 times than that of pure steam. The condensation heat transfer coefficients decreased with increased ethanol mass fraction in vapor. The vapor pressure and vapor velocity had a positive effect on the condensation heat transfer coefficients of ethanol-water vapor mixtures.
Chen, Xiping; Chong, Daotong; Wang, Jinshi; Huang, Ronghai; Yan, Junjie
Experimental investigation of convective heat transfer coefficient during downward laminar flow condensation of R134a in a vertical smooth tube
This paper presents an experimental investigation of laminar film condensation of R134a in a vertical smooth tube having an inner diameter of 7-8.1 mm and a length of 500 mm. Condensation experiments were performed at mass fluxes of 29 and 263 kg m ? 2 s ? 1 . The pressures were between 0.77 and 0.1 MPa. The heat transfer
A. S. Dalkilic; S. Yildiz; S. Wongwises
Numerical simulation and experimental analysis of heat transfer through the neck tube into vertical cryogenic insulated cylinders
The neck tube is an important support structure in cryogenic insulated cylinders. The heat flux from the outside environment\\u000a through the neck tube into the cryogenic liquid occupies a great proportion of the total heat leak and can be more than half\\u000a of the total heat loads. In this paper, conjugate convective-conductive heat transfer model between wall and the cold
Yang Li; Caili Wang; Rongshun Wang
Application of homotopy analysis method for natural convection of Darcian fluid about a vertical full cone embedded in pours media prescribed surface heat flux
In this paper, a powerful analytical method, called homotopy analysis method (HAM) is used to obtain the analytical solution for a nonlinear ordinary deferential equation that often appear in boundary layers problems arising in heat and mass transfer which these kinds of the equations contain infinity boundary condition. The boundary layer approximations of fluid flow and heat transfer of vertical full cone embedded in porous media give us the similarity solution for full cone subjected to surface heat flux boundary conditions. Nonlinear ODE which is obtained by similarity solution has been solved through homotopy analysis method (HAM). The main objective is to propose alternative methods of solution, which do not require small parameters and avoid linearization and physically unrealistic assumptions. The obtained analytical solution in comparison with the numerical ones represents a remarkable accuracy. The results also indicate that HAM can provide us with a convenient way to control and adjust the convergence region.
Sohouli, A. R.; Famouri, M.; Kimiaeifar, A.; Domairry, G.
Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2002
NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs. S. America ) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model. Review of other latent heating algorithms will be discussed in the workshop.
Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.
Free convection about a vertical flat plate embedded in a porous medium with application to heat transfer from a dike
An analysis is made for steady free convection about a vertical flat plate embedded in a saturated porous medium at high Rayleigh numbers. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xlambda, i.e., a power function of distance from the origin where wall temperature begins to deviate
Ping Cheng; W. J. Minkowycz
Vertical Profiles of Latent Heat Release Over the Global Tropics using TRMM Rainfall Products from December 1997 to November 2001
NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. Additional information is included in the original extended abstract.
Tao, W.-K.; Lang, S.; Simpson, J.; Meneghini, R.; Halverson, J.; Johnson, R.; Adler, R.; Starr, David (Technical Monitor)
NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2000. Rainfall, latent heating and radar reflectivity structures between El Nino (DJF 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs west Pacific, Africa vs S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in stratiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.
Vertical Profiles of Latent Heat Release over the Global Tropics using TRMM rainfall products from December 1997 to November 2001
NASA Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) derived rainfall information will be used to estimate the four-dimensional structure of global monthly latent heating and rainfall profiles over the global tropics from December 1997 to November 2001. Rainfall, latent heating and radar reflectivity structures between El Nino (DE 1997-98) and La Nina (DJF 1998-99) will be examined and compared. The seasonal variation of heating over various geographic locations (i.e., oceanic vs continental, Indian ocean vs. west Pacific, Africa vs. S. America) will also be analyzed. In addition, the relationship between rainfall, latent heating (maximum heating level), radar reflectivity and SST is examined and will be presented in the meeting. The impact of random error and bias in strtaiform percentage estimates from PR on latent heating profiles is studied and will also be presented in the meeting. The Goddard Cumulus Ensemble Model is being used to simulate various mesoscale convective systems that developed in different geographic locations. Specifically, the model estimated rainfall, radar reflectivity and latent heating profiles will be compared to observational data collected from TRMM field campaigns over the South China Sea in 1998 (SCSMEX), Brazil in 1999 (TRMM-LBA), and the central Pacific in 1999 (KWAJEX). Sounding diagnosed heating budgets and radar reflectivity from these experiments can provide the means to validate (heating product) as well as improve the GCE model.
The vertical distribution of radiogenic heat production in the Precambrian Crust of Norway and Sweden: Geothermal implications
The present geology of southern Scandinavia offers the unique opportunity to sample deep and intermediate levels from the same crustal section for both heat flow and heat production. In the central part ot southern Norway, amphibolite facies terranes appear to lie on top of the same deeper crustal formations which crop out on their western and eastern margins. An extensive
Christophe Pinet; Claude Jaupart
Heat transfer and pressure changes due to a large temperature difference across an enclosed vertical air layer
The TRACE-2D Code has been used to obtain non-Boussinesq results from transient, compressible and two-dimensional calculations using Sutherland law conductivity and viscosity property variations for air. These free convection results are limited to the laminar flow region. The aspect ratio A of the vertical air layer, with adiabatic top and bottom walls, is taken to be unity or greater, and
D. R. Chenoweth; S. Paolucci
Experimental study of forced convective heat transfer from a vertical tube conveying dilute Ag/DI water nanofluids in a cross flow of air
Forced convective heat transfer from a vertical circular tube conveying deionized (DI) water or very dilute Ag-DI water nanofluids (less than 0.02% volume fraction) in a cross flow of air has been investigated experimentally. Some experiments have been performed in a wind tunnel and heat transfer characteristics such as thermal conductance, effectiveness, and external Nusselt number has been measured at different air speeds, liquid flow rates, and nanoparticle concentrations. The cross flow of air over the tube and the liquid flow in the tube were turbulent in all cases. The experimental results have been compared and it has been found that suspending Ag nanoparticles in the base fluid increases thermal conductance, external Nusselt number, and effectiveness. Furthermore, by increasing the external Reynolds number, the external Nusselt number, effectiveness, and thermal conductance increase. Also, by increasing internal Reynolds number, the thermal conductance and external Nusselt number enhance while the effectiveness decreases.
Mohammadian, Shahabeddin Keshavarz; Layeghi, Mohammad; Hemmati, Mansor
Computational Treatment of MHD Transient Natural Convection Flow in a Vertical Channel Due to Symmetric Heating in Presence of Induced Magnetic Field
This paper considers the effect of induced magnetic field on transient hydromagnetic natural convection flow of an incompressible viscous electrically conducting fluid in the presence of transverse magnetic field in a vertical channel formed by electrically non-conducting infinite vertical parallel plates due to symmetric heating of vertical parallel plates. The problem is solved using Laplace transform technique and the inversion of the Laplace domain to the time domain is obtained by Riemann-sum approximation method. In order to verify the accuracy of Riemann-sum approximation method, analytical solution for steady state mathematical model is obtained in closed form. The governing equations are also solved using an implicit finite difference method to confirm the method used in the present problem. During the course of numerical computation an excellent agreement was found between steady state solution obtained exactly and transient solution obtained by implicit finite difference method or Riemann sum approximation method at large values of time. The dimensionless parameters in the flow are extensively discussed with the help of graphs.
Jha, Basant K.; Isa, Sani
Capital cost comparison of commercial ground-source heat pump systems.
The report provides a capital cost comparison of commercial ground source heat pump systems. The study includes groundwater systems, ground-coupled systems and hybrid systems. (ERA citation 19:033437)
K. Rafferty
Convective heat transfer to CO{sub 2} at a supercritical pressure flowing vertically upward in tubes and an annular channel
The Super-Critical Water-Cooled Reactor (SCWR) has been chosen by the Generation IV International Forum as one of the candidates for the next generation nuclear reactors. Heat transfer to water from a fuel assembly may deteriorate at certain supercritical pressure flow conditions and its estimation at degraded conditions as well as in normal conditions is very important to the design of a safe and reliable reactor core. Extensive experiments on a heat transfer to a vertically upward flowing CO{sub 2} at a supercritical pressure in tubes and an annular channel have been performed. The geometries of the test sections include tubes of an internal diameter (ID) of 4.4 and 9.0 mm and an annular channel (8 x 10 mm). The heat transfer coefficient (HTC) and Nusselt numbers were derived from the inner wall temperature converted by using the outer wall temperature measured by adhesive K-type thermocouples and a direct (tube) or indirect (annular channel) electric heating power. From the test results, a correlation, which covers both a deteriorated and a normal heat transfer regime, was developed. The developed correlation takes different forms in each interval divided by the value of parameter Bu. The parameter Bu (referred to as Bu hereafter), a function of the Grashof number, the Reynolds number and the Prandtl number, was introduced since it is known to be a controlling factor for the occurrence of a heat transfer deterioration due to a buoyancy effect. The developed correlation predicted the HTCs for water and HCFC-22 fairly well. (author)
Bae, Yoon-Yeong; Kim, Hwan-Yeol [Korea Atomic Energy Research Institute, 1045 Daedeokdaero, Yuseong, Daejeon 305-353 (Korea)
The TRACE-2D Code has been used to obtain non-Boussinesq results from transient, compressible and two-dimensional calculations using Sutherland law conductivity and viscosity property variations for air. These free convection results are limited to the laminar flow region. The aspect ratio A of the vertical air layer, with adiabatic top and bottom walls, is taken to be unity or greater, and the Rayleigh number Ra based on the layer width is as large as 10 to the 7th power when A = 1. The results are valid for large temperature differences between the hot and cold isothermal walls, epsilon = sub T(h) - sub T(c) or = 0.6, where the limitation is due to the Sutherland law accuracy. The various flow regimes are defined in terms of epsilon, A and Ra and correlations are developed for the Nusselt number and pressure in terms of these parameters. It is shown that, with proper non-dimensionalization, much of the vast body of literature concerning Nusselt number correlations and vertical temperature stratification for the Boussinesq case (which is asymptotically approached here for epsilon 1) can be used where epsilon is not small.
Chenoweth, D. R.; Paolucci, S.
Critical heat-flux experiments under low-flow conditions in a vertical annulus. [PWR; BWR; LMFBR
An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam-water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn-turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding-limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF.
Study of instabilities and quasi-two-dimensional turbulence in volumetrically heated magnetohydrodynamic flows in a vertical rectangular duct
We consider magnetohydrodynamic (MHD) rectangular duct flows with volumetric heating. The flows are upward, subject to a strong transverse magnetic field perpendicular to the temperature gradient, such that the flow dynamics is quasi-two-dimensional. The internal volumetric heating imitates conditions of a blanket of a fusion power reactor, where a buoyancy-driven flow is imposed on the forced flow. Studies of this mixed-convection flow include analysis for the basic flow, linear stability analysis and Direct Numerical Simulation (DNS)-type computations. The parameter range covers the Hartmann number (Ha) up to 500, the Reynolds number (Re) from 1000 to 10 000, and the Grashof number (Gr) from 105 to 5 � 108. The linear stability analysis predicts two primary instability modes: (i) bulk instability associated with the inflection point in the velocity profile near the ``hot'' wall and (ii) side-wall boundary layer instability. A mixed instability mode is also possible. An equation for the critical Hartmann number has been obtained as a function of Re and Gr. Effects of Ha, Re, and Gr on turbulent flows are addressed via nonlinear computations that demonstrate two characteristic turbulence regimes. In the ``weak'' turbulence regime, the induced vortices are localized near the inflection point of the basic velocity profile, while the boundary layer at the wall parallel to the magnetic field is slightly disturbed. In the ``strong'' turbulence regime, the bulk vortices interact with the boundary layer causing its destabilization and formation of secondary vortices that may travel across the flow, even reaching the opposite wall. In this regime, the key phenomena are vortex-wall and various vortex-vortex interactions. Flow and magnetic field effects on heat transfer are also analyzed.
Vetcha, N.; Smolentsev, S.; Abdou, M.; Moreau, R.
Effect of thermal-hydrogeological and borehole heat exchanger properties on performance and impact of vertical closed-loop geothermal heat pump systems
Ground-source geothermal systems are drawing increasing attention and popularity due to their efficiency, sustainability and being implementable worldwide. Consequently, design software and regulatory guidelines have been developed. Interaction with the subsurface significantly affects the thermal performance, sustainability, and impacts of such systems. Reviewing the related guidelines and the design software, room for improvement is evident, especially in regards to interaction with groundwater movement. In order to accurately evaluate the thermal effect of system and hydrogeological properties on a borehole heat exchanger, a fully discretized finite-element model is used. Sensitivity of the loop outlet temperatures and heat exchange rates to hydrogeological, system and meteorological factors (i.e. groundwater flux, thermal conductivity and volumetric heat capacity of solids, porosity, thermal dispersivity, grout thermal conductivity, background and inlet temperatures) are analyzed over 6-month and 25-year operation periods. Furthermore, thermal recovery during 25 years after system decommissioning has been modeled. The thermal plume development, transport and dissipation are also assessed. This study shows the importance of subsurface thermal conductivity, groundwater flow (flux > 10-7 m/s), and background and inlet temperature on system performance and impact. It also shows the importance of groundwater flow (flux > 10-8 m/s) on thermal recovery of the ground over other factors.
Dehkordi, S. Emad; Schincariol, Robert A.
An analytical study on heat and mass transfer for ammonia-water system in a vertical falling-film type of absorber and generator
A numerical analysis on simultaneous heat and mass transfer for ammonia-water air-conditioning with a vertical falling-film type of absorber and generator was performed by the one-dimensional difference method which takes into account only the change of flow direction. In the calculation, the geometries of absorber/generator and the temperature conditions were taken like as those in our previous works for water-lithium bromide system. Therefore, the liquid and vapor concentrations ranged 53-55 and 99-l00mass%NH3, respectively. The ratio of the liquid mass flow rate to the vapor mass flow rate, L/V, ranged up to 18000. For these thermal conditions, it was found that the vapor-phase mass transfer resistance is negligibly small, and the absorption/generation rates are almost constant regardless of the vapor flow rate, but increase with increasing liquid flow rate. It was also found that the calculated values of heat fluxes in the absorber/generator for ammonia-water system are equivalent or superior to those for water-lithium bromide system.
Honda, Katsumi; Matsuda, Akira
Multisensor Observations of the Lifecycles of Propagating Tropical Convective Systems: Horizontal and Vertical Structure, Diabatic Heating and Moistening, and Relationship to Environmental Parameters
Tropical oceanic convective systems are identified and tracked through use of the CMORPH high-resolution rainfall product. The composite areal coverage of rainfall (provided by TRMM PR and CMORPH), convective/stratiform ratio (from TRMM PR), vertical extent of the raining system (TRMM PR) and the diabatic heating and moistening tendencies (Q1-QR, Q2 from the Spectral Latent Heating Algorithm product) are all quantified, as a function of both system lifecycle stage and system longevity. System longevity is shown to have strong relationships with environmental shear and humidity. The composite changes in total precipitable water (TPW) and SST (from the GHRSST product) along the paths of the systems are discussed, both as a function of system stage and longevity. Unlike the composite convective events, individual systems undergo both systematic and random variations in terms of convective organization, surface rainfall characteristics, and propagation direction as their lifecycle proceeds. These variations are investigated as a function of varying environmental shear along the path of system (provided from NCEP re-analysis), the distribution of water vapor surrounding the system (from AIRS Version-6 0.25-degree product), and newly derived QuikSCAT-based 'triggering energy' (often associated with convergence zones at the edges of large cold pools) that is a function of both the system in question as well as near-vicinity convection.
Elsaesser, G.; Li, Y.; Kummerow, C. D.; Carbone, R. E.
Vapor compression heat pump system field tests at the tech complex
The Tennessee Energy Conservation In Housing (TECH) complex has been utilized since 1977 as a field test site for several novel and conventional heat pump systems for space conditioning and water heating. Systems tested include the Annual Cycle Energy System (ACES), solar assisted heat pumps (SAHP) both parallel and series, two conventional air-to-air heat pumps, an air-to-air heat pump with desuperheater water heater, and horizontal coil and multiple shallow vertical coil ground-coupled heat pumps (GCHP). A direct comparison of the measured annual performance of the test systems was not possible. However, a cursory examination revealed that the ACES had the best performance, however, its high cost makes it unlikely that it will achieve wide-spread use. Costs for the SAHP systems are similar to those of the ACES but their performance is not as good. Integration of water heating and space conditioning functions with a desuperheater yielded significant efficiency improvement at modest cost. The GCHP systems performed much better for heating than for cooling and may well be the most efficient alternative for residences in cold climates.
Baxter, Van D.
Vapor compression heat pump system field tests at the TECH complex
The Tennessee Energy Conservation In Housing (TECH) complex has been utilized since 1977 as a field test site for several novel and conventional heat pump systems for space conditioning and water heating. Systems tested include the Annual Cycle Energy System (ACES), solar assisted heat pumps (SAHP) both parallel and series, two conventional air-to-air heat pumps, an air-to-air heat pump with desuperheater water heater, and horizontal coil and multiple shallow vertical coil ground-coupled heat pumps (GCHP). A direct comparison of the measured annual performance of the test systems was not possible. However, a cursory examination revealed that the ACES had the best performance. However, its high cost makes it unlikely that it will achieve widespread use. Costs for the SAHP systems are similar to those of the ACES but their performance is not as good. Integration of water heating and space conditioning functions with a desuperheater yielded significant efficiency improvement at modest cost. The GCHP systems performed much better for heating than for cooling and may well be the most efficient alternative for residences in cold climates.
Baxter, V. D.
The role of diabatic heating, torques and stabilities in forcing the radial-vertical circulation within cyclones part ii: case study of extratropical and tropical cyclones
Utilizing Eliassen's concepts, the forcing of the isentropic azimuthally-averaged mass-weighted radial-vertical circulation by diabatic heating and torques within an extratropical cyclone and a typhoon was studied through numerical simulations based on the linear diagnostic equation derived previously. The structure of the forcing associated with diabatic heating and torques was determined from quasi-Lagrangian diagnostic analyses of actual case studies. The two cyclones studied were the Ohio extratropical cyclone of 25-27 January 1978 and typhoon Nancy of 18-23 September 1979. The Ohio cyclone, which formed over the Gulf Coast and moved through Ohio and eastern Michigan, was one of the most intense storms with blizzard conditions to ever occur in this region. Typhoon Nancy which occurred over the South China Sea during the FGGE year was selected since relatively high quality assimilated data were available. Within the Ohio cyclone, the dominant internal processes forcing the mean circulation with embedded relatively strong hydrodynamic stability were the pressure torque associated with baroclinic (asymmetric) structure and the horizontal eddy angular momentum transport associated with the typical S-shaped thermal and wind structures of self-development. Within typhoon Nancy, the dominant internal process forcing the mean circulation with embedded weak hydrodynamic stability was the latent heat release. This analysis shows that the simulated azimuthally-averaged mass-weighted radial motions within these two cyclones agree quite well with the � observed? azimuthally-averaged mass-weighted radial motions. This isentropic numerical study also provides insight into the relatively important internal forcing processes and the trade off between forcing and stability within both extratropical and tropical cyclones.
Yuan, Zhuojian; Johnson, Donald R.
Effects of Surface Heat Flux Anomalies on Stratification, Convective Growth and Vertical Transport within the Saharan Boundary Layer
The very large surface sensible and very low latent heat fluxes in the Sahara desert lead to its unusually deep, almost dry-adiabatic boundary layer, that often reaches 6 km. This is often observed to consist of a shallow convective boundary layer (CBL) with a near neutral residual layer above (the Saharan Residual Layer, or SRL). It has been shown that the SRL can be both spatially extensive and persist throughout the day. Multiple near-neutral layers are frequently observed within the SRL, or within the SAL, each with a different water vapour and/or dust content, and each separated by a weak lid (e.g., Figure 1). A local maximum in not only relative humidity, but also water vapour mixing ratio (WVMR) is often seen at the top of the SRL or SAL. This structure suggests that in some locations, at some times, convection from the surface is mixing the full depth of the Saharan boundary layer, but in most locations and times this is not the case, and varying horizontal advection leads to the multiple layering observed. During the GERBILS (GERB Intercomparison of Longwave and Shortwave radiation) field campaign in the Sahara, coherent couplings were observed between surface albedo, CBL air temeperatures and CBL winds. Using two cases based on observations from GERBILS, large eddy model (LEM) simulations have been used to investigate the effects of surface flux anomalies on the growth of the summertime Saharan CBL into the Saharan Residual layer (SRL) above, and transport from the CBL into the SRL. Hot surface anomalies generated updraughts and convergence in the CBL that increased transport from the CBL into the SRL. The induced subsidence in regions away from the anomalies inhibited growth of the CBL there. If the domain-averaged surface fluxes were kept constant this led to a shallower, cooler CBL. If fluxes outside the anomalies were kept constant, so that stronger anomalies led to increased domain-averaged fluxes, this gave a warmer, shallower CBL. These effects were larger for wider, stronger anomalies, with low winds. These LEM simulations show that mesoscale variations in surface fluxes can contribute to both inhibiting the growth of the Saharan CBL into the SRL, and generating layerings within the SRL.
Huang, Qian; Marsham, John; Parker, Doug; Tian, Wenshou; Grams, Christian; Cuesta, Juan; Flamant, Cyrille
Vertical Disintegration
With economies of scale, a vertically integrated firm can lower its upstream cost by supplying downstream competitors. The competitors may strategically choose not to purchase from the integrated firm, unless the latter's price for the intermediate good is sufficiently lower than those of alternative suppliers. In a simple model of dynamic scale economies through learning by doing, equilibrium vertical disintegration
Yongmin Chen
Steady MHD free convection heat and mass transfer flow about a vertical porous surface with thermal diffusion and induced magnetic field
In this study the thermal diffusion effect on the steady laminar free convection flow and heat transfer of viscous incompressible MHD electrically conducting fluid above a vertical porous surface is considered under the influence of an induced magnetic field. The governing non-dimensional equations relevant to the problem, containing the partial differential equations, are transformed by usual similarity transformations into a system of coupled non-linear ordinary differential equations and will be solved analytically by using the perturbation technique. On introducing the non-dimensional concept and applying Boussinesq's approximation, the solutions for velocity field, temperature distribution and induced magnetic field to the second order approximations are obtained for large suction with different selected values of the established dimensionless parameters. The influences of these various establish parameters on the velocity and temperature fields and on the induced magnetic fields are exhibited under certain assumptions and are studied graphically in the present analysis. It is observed that the effects of thermal-diffusion and large suction have great importance on the velocity, temperature and induced magnetic fields and mass concentration for several fluids considered, so that their effects should be taken into account with other useful parameters associated. It is also found that the dimensionless Prandtl number, Grashof number, Modified Grashof number and magnetic parameter have an appreciable influence on the concerned independent variables.
Touhid Hossain, M. M.; Afruz-Zaman, Md.; Rahman, Fouzia; Hossain, M. Arif
Sustainable Cooling via a Ground Coupled Chilled Ceiling System - A Theoretical Investigation (UK6.M1P)
SUMMARY Traditional cooling systems are large contributors to global warming and ozone depletion and this has provided opportunities for new sustainable methods of cooling buildings. One approach that has recently been reported involves an integrated system utilising ground source heat exchangers and chilled ceilings to provide sustainable cooling. This paper describes a study into the practicalities and economics of applying
G. G. Maidment; J. F. Missenden
'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.
Albert, Stephen L.; Spencer, Jeffrey B.
Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997
Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.
Allan, M.L.
Viscous dissipation and Joule heating effects on MHD-free convection from a vertical plate with power-law variation in surface temperature in the presence of Hall and ion-slip currents
An analysis is presented to study the effects of viscous dissipation and Joule heating on MHD-free convection flow past a semi-infinite vertical flat plate in the presence of the combined effect of Hall and ion-slip currents for the case of power-law variation of the wall temperature. The fluid is permeated by a strong transverse magnetic field imposed perpendicularly to the
Emad M. Abo-Eldahab; Mohamed A. El Aziz
Vertical mammaplasty.
Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques. PMID:15793463
Hidalgo, David A
Comparative Study Between a Geothermal Heat Pump System and an Air-to-Water Heat Pump System for Heating and Cooling in Typical Conditions of the European Mediterranean Coast
To make a overall assessment of a Ground Coupled Heat Exchanger (GCHE) it is not only important to understand the behaviour of the GCHE, but also to consider the system in which it will operate: its loads and utilization factors (as a function of climate conditions and application), efficiency (which also depends on the heat pump) and other system parameters,
G. Romero; J. F. Urchuegu�a; H. Witte; W. Cambien; T. Magraner
Simple computer program to model 3-dimensional underground heat flow with realistic boundary conditions
A FORTRAN computer program called GROCS (GRound Coupled Systems) has been developed to study 3-dimensional underground heat flow. Features include the use of up to 30 finite elements or blocks of Earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth dependent boundary conditions. No explicit consideration of mositure movement or freezing
P. D. Metz
A simple computer program to model three-dimensional underground heat flow with realistic boundary conditions
A FORTRAN computer program called GROCS (Ground Coupled Systems) has been developed to study three-dimensional underground heat flow. Features include the use of up to 30 finite elements or ''blocks'' of earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth-dependent boundary conditions. No explicit consideration of moisture movement or freezing is
Thermal radiation effect on mixed convection heat and mass transfer of a non-Newtonian fluid over a vertical surface embedded in a porous medium in the presence of thermal diffusion and diffusion-thermo effects
Thermal radiation, thermal diffusion, and diffusion-thermo effects on heat and mass transfer by mixed convection of non-Newtonian power-law fluids over a vertical permeable surface embedded in a saturated porous medium are investigated. The governing equations describing the problem are non-dimensionalized and transformed into a non-similar form. The transformed equations are solved by using the local non-similarity method combined with the shooting technique. The effects of the physical parameters of the problem on the fluid temperature and concentration are illustrated graphically and analyzed. Also, the effects of the pertinent parameters on the local Nusselt number and the local Sherwood number are presented.
Mahmoud, M. A. A.; Megahed, A. M.
Analysis of the critical heat flux in round vertical tubes under low pressure and flow oscillation conditions. Applications of artificial neural network
Artificial neural networks (ANNs) for predicting critical heat flux (CHF) under low pressure and oscillation conditions have been trained successfully for either natural circulation or forced circulation (FC) in the present study. The input parameters of the ANN are pressure, mean mass flow rate, relative amplitude, inlet subcooling, oscillation period and the ratio of the heated length to the diameter
Su Guanghui; K Morita; K Fukuda; Mark Pidduck; Jia Dounan; Jaakko Miettinen
Radiation and thermal diffusion effects on an unsteady MHD free convection mass-transfer flow past an infinite vertical porous plate with the hall current and a heat source
An analysis is performed to study the effects of radiation and thermal diffusion on an unsteady MHD free convection heat- and mass-transfer flow of an incompressible, electrically conducting, viscous fluid past an infinite vertical porous plate with the Hall current and a heat source. The flow is considered under the influence of a constant suction velocity and a uniform magnetic field applied normally to the flow. The dimensionless governing equations are solved numerically by the Galerkin finite element method. The effects of the flow parameters on the primary and secondary velocities, temperature, species concentration, shearing stresses, Nusselt number, and Sherwood number are calculated and presented in figures and tables. The results obtained show that a decrease in the temperature boundary layer thickness occurs when the Prandtl number and radiation parameter are increased and an increase in the Schmidt number leads to a decrease in the concentration boundary layer thickness.
Reddy, B. Prabhakar; Rao, J. Anand
Convective flow past a vertical plate under the influence of magnetic field and thermal radiation subjected to a variable surface temperature in the presence of heat source/sink
In the present analysis, a numerical study is performed to examine the heat transfer characteristics of a convective flow over a vertical plate under the combined effects of magnetic field and thermal radiation in the presence of heat source/sink. The surface of the plate is subjected to a variable surface temperature. The boundary layer equations governing the flow are reduced to non-dimensional equations valid in the free convection regime using the suitable non-dimensional parameters. The dimensionless governing equations are solved by an implicit finite difference method of Crank�Nicolson type which is fast convergent, more accurate and unconditionally stable. Numerical results are obtained and presented for velocity, temperature, local and average wall shear stress, local and average Nusselt number in air. The present results are compared with the results available in the literature and are found to be in an excellent agreement.
Reddy, P. B. A.; Reddy, N. B.; Palani, G.
Experimental investigation of heat transfer coefficient of R134a during condensation in vertical downward flow at high mass flux in a smooth tube
The two-phase heat transfer coefficients of pure HFC-134a condensing inside a smooth tube-in-tube heat exchanger are experimentally investigated. The test section is a 0.5�m long double tube with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is constructed from smooth copper tubing of 9.52�mm outer diameter and 8.1�mm inner diameter. The test
A. S. Dalkilic; S. Laohalertdecha; S. Wongwises
A numerical analysis of solid-liquid phase change heat transfer around a single and two horizontal, vertically spaced cylinders in a rectangular cavity
In the present study, a new numerical model is proposed to analyze solid-liquid phase change heat transfer in a complicated geometry. The present model can treat the solid\\/liquid phase change heat transfer with\\/without porous media, as well as conventional transient natural convection with\\/without porous media. Solidification calculations of pure water (without porous media) around a single cylinder and two cylinders
R. Viskanta
Vertical Profiles of Latent Heat Release and Their Retrieval for TOGA COARE Convective Systems Using a Cloud Resolving Model, SSM/I, and Ship-borne Radar Data
Latent heating profiles associated with three (TOGA COARE) Tropical Ocean and Global Atmosphere Coupled Ocean Atmosphere Response Experiment active convective episodes (December 10-17 1992; December 19-27 1992; and February 9-13 1993) are examined using the Goddard Cumulus Ensemble (GCE) Model and retrieved by using the Goddard Convective and Stratiform Heating (CSH) algorithm . The following sources of rainfall information are input into the CSH algorithm: Special Sensor Microwave Imager (SSM/1), Radar and the GCE model. Diagnostically determined latent heating profiles calculated using 6 hourly soundings are used for validation. The GCE model simulated rainfall and latent heating profiles are in excellent agreement with those estimated by soundings. In addition, the typical convective and stratiform heating structures (or shapes) are well captured by the GCE model. Radar measured rainfall is smaller than that both estimated by the GCE model and SSM/I in all three different COARE IFA periods. SSM/I derived rainfall is more than the GCE model simulated for the December 19-27 and February 9-13 periods, but is in excellent agreement with the GCE model for the December 10-17 period. The GCE model estimated stratiform amount is about 50% for December 19-27, 42% for December 11-17 and 56% for the February 9-13 case. These results are consistent with large-scale analyses. The accurate estimates of stratiform amount is needed for good latent heating retrieval. A higher (lower) percentage of stratiform rain can imply a maximum heating rate at a higher (lower) altitude. The GCE model always simulates more stratiform rain (10 to 20%) than the radar for all three convective episodes. SSM/I derived stratiform amount is about 37% for December 19-27, 48% for December 11-17 and 41% for the February 9-13 case. Temporal variability of CSH algorithm retrieved latent heating profiles using either GCE model simulated or radar estimated rainfall and stratiform amount is in good agreement with that diagnostically determined for all three periods. However, less rainfall and a smaller stratiform percentage estimated by radar resulted in a weaker (underestimated) latent heating profile and a lower maximum latent heating level compared to those determined diagnostically. Rainfall information from SSM/I can not retrieve individual convective events due to poor temporal sampling. Nevertheless, this study suggests that a good 4r, rainfall retrieval from SSM/I for a convective event always leads to a good latent heating retrieval. Sensitivity testing has been performed and the results indicate that the SSM/I derived time averaged stratiform amount may be underestimated for December 19-27. Time averaged heating profiles derived from SSM/I, however, are not in bad agreement with those derived by soundings for the December 10-17 convective period. The heating retrievals may be more accurate for longer time scales provided there is no bias in the sampling.
Tao, Wei-Kuo; Lang, S.; Simpson, J.; Olson, W. S.; Johnson, D.; Ferrier, B.; Kummerow, C.; Adler, R.
Vertical Launch Third Harmonic Electron Cyclotron Resonance Heating of H-mode on TCV and Access to Quasi-Stationary ELM-free H-mode
The Tokamak a Configuration Variable (TCV) is equipped with three 480 kW gyrotrons operating at 118 GHz. Radiation is launched in the extraordinary mode allowing plasma heating using third harmonic X-mode electron cyclotron resonance heating (ECRH) at density up to 11x10{sup 19} m{sup -3}. Power is transmitted to the tokamak along 3 evacuated waveguides and is projected onto one plasma facing mirror that can be translated radially, between shots, and rotated poloidally during a shot. Linear ray-tracing is adequate tool for estimating the X3 coupled power in H-mode plasma and all estimates of X3 coupled power presented in this paper have been obtained using ray tracing. Experiments were performed to heat H-mode using X3. The target was an ohmic H-mode. Up to 90% of the launched X3 power was coupled to the plasma so that the total heating power (1.3 MW) was about much greater than the ohmic H-mode threshold power (500 kW). This level of coupled power was maintained even in the presence of significant perturbations to the plasma; ELMS. The radiated power was 300 kW during the X3 heated phase. The X3 heated H-mode discharges often transited into an ELM free H-mode regime with constant electron density and stored energy. During the X3 phase the stored energy and {beta}{sub tor} both doubled ({beta}{sub N} = 2). The maximum, achieved {beta}{sub tor} was 2.5% while the ideal {beta}-limit for these discharges was 3.5%. The recycling light level was high compared to the baseline ohmic H-mode level and the fluctuations in the recycling light level were correlated with core MHD. The confinement time for these discharges was found to be as high as 30 ms (HIPB(y,2) = 1.7). Measurements of carbon ion temperature profiles and carbon rotation velocity using charge exchange recombination spectroscopy showed that the ion temperature, near mid radius, increased from 500 eV to 1 keV during the quiescent phase. The plasma rotation increased also from 5 kms{sup -1} to 5 kms{sup -1} in the direction of plasma current.
Porte, L. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, CRPP EPFL, Association EURATOM--Confederation Suisse, 1015 Lausanne (Switzerland)
Finite element analysis of MHD mixed convection heat transfer enhancement of a heat-generating block in a double lid-driven enclosure filled with air at different vertical location
m Abstract- Tbe present numerical study is conducted to investigate MHD mixed convection flow and beat transfer cbaracteristics in a double-lid driven cavity witb a beat� generating solid square block. Tbe cavity borimntal walls are adiabatic while both the vertical lids are maintained at a uniform temperature Tc and velocity Vo-Tbe present study simulates a reasonable system such as air-cooled
M. M. Billaha; M. M. Rahmanc; M. S. Uddine; M. Shahabuddina
Downflow dryout in a heated ribbed vertical annulus with a cosine power profile (Results from test series ECS-2, WSR, and ECS-2cE)
Experiments designed to investigate surface dryout in a heated, ribbed annulus test section simulating one of the annular coolant channels of a Savannah River Plant production reactor Mark 22 fuel assembly have been conducted at the Idaho National Engineering Laboratory. The inner surface of the annulus was constructed of aluminum and was electrically heated to provide an axial cosine power profile and a flat azimuthal power shape. Data presented in this report are from the ECS-2, WSR, and ECS-2cE series of tests. These experiments were conducted to examine the onset of wall thermal excursion for a range of flow, inlet fluid temperature, and annulus outlet pressure. Hydraulic boundary conditions on the test section represent flowrates (0.1--1.4 1/s), inlet fluid temperatures (293--345 K), and outlet pressures (-18--139.7 cm of water relative to the bottom of the heated length (61--200 cm of water relative to the bottom of the lower plenum)) expected to occur during the Emergency Coolant System (ECS) phase of postulated Loss-of-Coolant Accident in a production reactor. The onset of thermal excursion based on the present data is consistent with data gathered in test rigs with flat axial power profiles. The data indicate that wall dryout is primarily a function of liquid superficial velocity. Air entrainment rate was observed to be a strong function of the boundary conditions (primarily flowrate and liquid temperature), but had a minor effect on the power at the onset of thermal excursion for the range of conditions examined. 14 refs., 33 figs., 13 tabs.
Larson, T.K.; Anderson, J.L.; Condie, K.G.
Heat transfer to and from a reversible thermosiphon placed in porous media
The primary focus of this work is an assessment of heat transfer to and from a reversible thermosiphon imbedded in porous media. The interest in this study is the improvement of underground thermal energy storage (UTES) system performance with an innovative ground coupling using an array of reversible (pump-assisted) thermosiphons for air conditioning or space cooling applications. The dominant mechanisms, including the potential for heat transfer enhancement due to natural convection, of seasonal storage of "cold" in water-saturated porous media is evaluated experimentally and numerically. Winter and summer modes of operation are studied. A set of 6 experiments are reported that describe the heat transfer in both fine and coarse sand in a 0.32 cubic meter circular tank, saturated with water, under freezing (due to heat extraction) and thawing (due to heat injection) conditions, driven by the heat transfer to or from the vertical thermosiphon in the center of the tank. It was found that moderate to strong natural convection was induced at Rayleigh numbers of 30 or higher. Also, near water freezing temperatures (0�C-10�C), due to higher viscosity of water at lower temperatures, almost no natural convection was observed. A commercial heat transfer code, ANSYS FLUENT, was used to simulate both the heating and cooling conditions, including liquid/solid phase change. The numerical simulations of heat extraction from different permeability and temperature water-saturated porous media showed that enhancement to heat transfer by convection becomes significant only under conditions where the Rayleigh number is in the range of 100 or above. Those conditions would be found only for heat storage applications with higher temperatures of water (thus, its lower viscosity) and large temperature gradients at the beginning of heat injection (or removal) into (from) soil. For "cold" storage applications, the contribution of natural convection to heat transfer in water-saturated soils would be negligible. Thus, the dominant heat transfer mechanism for air conditioning applications of UTES can be assumed to be conduction. An evaluation of the potential for heat transfer enhancement in air-saturated media is also reported. It was found that natural convection in soils with high permeability and air saturations near 1 becomes more important as temperatures drop significantly below freezing.
Kekelia, Bidzina
Convective Instabilities in Vertical Fractures and Faults
Natural convection of water contained in a vertical fracture or fault in which the temperature increases with depth is strongly influenced by the heat transport processes not only within the water itself but also by the heat transferred to and from the surrounding rock mass. The results of a linear stability analysis indicate that the critical Rayleigh number R* is
Hugh D. Murphy; Geosciences Division
Vertical bounce of two vertically aligned balls
When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.
Cross, Rod
Vertical axis wind turbines
A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.
Krivcov, Vladimir (Miass, RU) [Miass, RU; Krivospitski, Vladimir (Miass, RU) [Miass, RU; Maksimov, Vasili (Miass, RU) [Miass, RU; Halstead, Richard (Rohnert Park, CA) [Rohnert Park, CA; Grahov, Jurij (Miass, RU) [Miass, RU
Experimental comparison of retrofit vertical air collectors
Two vertical air collector systems were built and monitored. One of these is a back-pass collector in which a layer of sheet metal serves as the absorber plate. The other is a front pass collector in which the wall surface serves as the absorber plate. The results demonstrate the importance of considering heat moving through walls even when storage of heat in the wall is of limited significance. With poorly insulated walls, heat is better able to move through the wall with a front pass collector, indicating that this type of collector is a more effective heating system.
Wilson, A.T.; Stickney, B.L.
Vertical axis windmill
A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.
Campbell, J.S.
Vertical axis wind turbine
A Darrieus-type vertical axis wind turbine is disclosed which includes a vertically extending rotor tube mounted on a support structure with two or three rotor blades of troposkein configuration on the rotor tube for rotating the tube in response to wind energy and thereby drive a generator to produce electrical power. The turbine includes an erection hinge which permits assembly
Vertikale temperaturgradienter i rum med konvektive stroemninger. (Vertical temperature gradients in rooms with convective air flow).
This project deals with measuring and calculation of vertical temperature gradients in radiator heated rooms and measuring of similar vertical gradients in rooms ventilated by displacement ventilation. The project focuses on experimental and theoretical e...
H. Overby
Vertical two chamber reaction furnace
A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.
Blaugher, Richard D. (Evergreen, CO)
A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.
Blaugher, R.D.
Vertical Line Test
NSDL National Science Digital Library
In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.
On the Vertical Stability of a Rotating Fluid Subject to a Horizontal Temperature Gradient
The vertical potential temperature gradient in the atmosphere is the result of heat transport by radiation and by small- and large-scale motions, with complications due to latent heat release and absorption in condensation and cloud. An idealized model, characterized by the absence of latent heat effects and of a vertical component to the gradient of the impressed temperature field, is
R. Hide
Micromachined electrostatic vertical actuator
A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.
Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)
Paroxysmal Vertical Ocular Dyskinesia.
Paroxysmal vertical ocular dyskinesia of a previously undescribed nature is reported in a 42-year old woman with demyelinating disease, who was affected with a myelopathy, bilateral amblyopia, and a modified sylvian aqueduct syndrome. Electroencephalograp...
J. B. MacLean J. F. Sassin
Ground energy coupling
The feasibility of ground coupling for various heat pump systems was investigated. Analytical heat flow models were developed to approximate design ground coupling devices for use in solar heat pump space conditioning systems. A digital computer program called GROCS (GRound Coupled Systems) was written to model 3-dimensional underground heat flow in order to simulate the behavior of ground coupling experiments and to provide performance predictions which have been compared to experimental results. GROCS also has been integrated with TRNSYS. Soil thermal property and ground coupling device experiments are described. Buried tanks, serpentine earth coils in various configurations, lengths and depths, and sealed vertical wells are being investigated. An earth coil used to heat a house without use of resistance heating is described.
Metz, P. D.
Verticality in hydroelectric machines
Everyone who erects a vertical hydroelectric machine makes an effort to put the machine together so that its elements are vertical. A plumb line (or its optical equivalent) is a practical starting point for aligning the stationary parts of the machine - the generator stator, turbine case, and bearings. This does not mean, though, that the machine parts must be in near-perfect vertical orientation for the machine to perform well. Verticality is sometimes over-emphasized when procedures are undertaken to achieve good machine alignment. If the generator rotor, the connecting shaft, and the turbine runner are centered in stationary parts that are well-aligned along the same axis angle, this angle can depart from true vertical by a significant amount without ill effect. Mechanical balance does not often play a large part in determining how well a generator rotor is centered in the air gap. Magnetic forces are much more important. This is why it is desirable to maintain air gap variations around the machine to less than 5 percent from the average. However, this is sometimes difficult, especially if bearing clearances are large.
O'Kelly, F.
Enhancement of Condensation on a Vertical Plate
In previous study, the characteristic of the condensation heat transfer on the dispersed vertical surface were investigated experimentally for the application of the finned surface to the thermoelectric generator utilizing boiling and condensation as the electrodes of the thermoelectric module. A prediction model for this diapered finned surface was proposed, based on Adamek-Webb model of the condensation on a finned tube. In this study, a condensation heat transfer experiment on a vertical dispersed finned surfaces using FC5312 was carried out, in order to enhance the condensation heat transfer coefficient by optimizing the fin size on a dispersed heat transfer surface. The object of the experiment was limited to the rectangular fin with the height of 3 mm. Experimental parameters were the temperature difference, the fin groove width, the fin thickness and the dispersing size on the vertical direction. As the results, it was found from the experiment that the dependence of the condensation heat transfer coefficient on the dispersed size is controlled by the fin groove width. That is, the condensation heat transfer coefficient will increase for a smaller fin groove width and will decrease for a larger fin groove width, with decreasing of the dispersing size. Moreover, there is an optimum fin thickness at which the condensation heat transfer coefficient becomes the maximum in the case of constant fin groove width for both size of the fin groove width. This effect of the fin thickness is more significant for the smaller fin groove width. Further, the prediction values exhibit a good agreement with the experimental data in the present experiment.
Chu, Rencai; Hatanaka, Tsutomu; Nishio, Shigefumi
Vertical structuring of gigantic jets
Gigantic Jets (GJs) are initiated deep inside the thundercloud as intracloud discharges whose upward-directed leaders manage to escape through the thundercloud top and propagate up to the ionosphere. The speed at which leaders propagate is limited by the air heating of every newly formed leader section, rate of which is slower at upper altitudes in the Earth's atmosphere. Despite the expected deceleration of an upward-directed leader, GJs are observed to accelerate as they approach the ionosphere. In this letter, we discuss the dependence of the leader speed on current density in the leader stem, and we propose a simple time-dynamic model for GJ propagation that includes the effects of the expansion of the streamer zone adjacent to the leader head. We propose that the GJ acceleration is a consequence of its vertical structuring and, therefore, can be used to trace the transition altitude between the leader and streamer zone sections of GJs.
Silva, Caitano L.; Pasko, Victor P.
Vertical winds in the central polar cap
Upward vertical winds are observed in the polar cap F-region over Eureka (80�N) during and following sustained polar auroras. This suggests that heating due to particle energy deposition in the F-region is sufficient to generate upward flow. At such times there is a positive divergence in the horizontal winds, indicating that the upward flow is also outward over a >1000 km diameter across the central polar cap. The vertical winds, averaged over a 5-winter period, also have a positive correlation with the horizontal divergences indicating the flow is generally large scale. Downward winds are seen to similarly correspond with negative divergences, and negative IMF Bz, suggesting they may be linked with activity at auroral latitudes. Vertical winds observed over Eureka at other times, appear to be oscillatory with 12-hr and higher harmonic periods suggesting tidal activity. This preliminary conclusion will be tested by examining further winds and aeronomic data.
Guo, W.; McEwen, D. J.
Vertical emitting aperture nanoantennas.
Herein we propose, theoretically investigate, and numerically demonstrate a compact design for a vertical emitter at a wavelength of 1.5 ?m based on nanophotonic aperture antennas coupled to a dielectric waveguide. The structure utilizes a plasmonic antenna placed above a Si3N4 waveguide with a ground plane for breaking the up-down symmetry and increasing the emission efficiency. Three-dimensional (3-D) finite-difference time-domain (FDTD) simulations reveal that up to 60% vertical emission efficiency is possible in a structure only four wavelengths long with a 3 dB bandwidth of over 300 nm. PMID:22555702
Yaacobi, Ami; Timurdogan, Erman; Watts, Michael R
Vertical breast reduction.
The vertical approach to breast reduction surgery has achieved increasing popularity. The learning curve can be a problem for surgeons starting to incorporate vertical techniques into their practices; the medial pedicle approach is outlined in detail. Designing and creating the medial pedicle is straightforward and rotating it into position is easy. An elegant curve to the lower pole of the reduced breast can thus be created. Current concepts related to the skin brassiere, breast sutures, and the longevity of results are reviewed. It is important for the surgeon to understand that the skin resection pattern and the pedicle design are separate issues when discussing breast reduction surgery. PMID:20574477
Hall-Findlay, Elizabeth J
A vertical axis windmill has a blade pivotally connected to a rotatable support structure on an axis passing through its center of gravity which is arranged to lie forward of its aerodynamic center whereby the blade automatically swings outwardly and inwardly when moving on the windward and leeward sides respectively of the axis of rotation of said support means.
Zheug, Y.K.
Vertical shaft windmill
A vertical shaft has several equally spaced blades mounted thereon. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.
Grana, D.C.; Inge, S.V. Jr.
A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.
Grana, D. C.; Inge, S. V., Jr. (inventors)
Improved vertical scanning interferometry
Vertical scanning interferometers are routinely used for the measurement of optical fiber connectors. There are increasing needs for measurements of such items as machined surfaces, contact lenses, paint texture, cell structure, and integrated circuit devices, to name a few. These structures have too much depth, or are too rough, to measure with standard interferometry methods. Phase- measurement interferometry methods are
Akiko Harasaki; Joanna Schmidt; James C. Wyant
Developing Vertical File Resources.
Describes how to develop vertical file resources for school libraries. Discusses the importance of having primary sources that are not available in other formats; sources for obtaining materials, including the Internet and printed sources; how to organize the materials; providing access; and promoting the collection. (LRW)
Smallwood, Carol
Aiding Vertical Guidance Understanding
A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.
Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen
Upward vertical winds are observed in the polar cap F-region over Eureka (80�N) during and following sustained polar auroras. This suggests that heating due to particle energy deposition in the F-region is sufficient to generate upward flow. At such times there is a positive divergence in the horizontal winds, indicating that the upward flow is also outward over a >1000
W. Guo; D. J. McEwen
Thermal analysis of vertically integrated circuits
In this paper, a thermal analysis of Vertically Integrated Circuits (VIC) is presented for the first time. Based on a 1-D model, temperature differences in VICs of less than 10�C are evaluated for most practical applications. Detailed 3-D investigations show that self-heating of MOSFETs in the upper chip-layers of a VIC is more pronounced than in bulk CMOS and that
M. B. Kleiner; S. A. Kuhn; P. Ramm; W. Weber
A new method to simulate vertical and horizontal structure in galactic disks
We have modified the particles in an N-body treecode to have different softening lengths in the horizontal and vertical directions. This allows us to simultaneously have thin enough particles to resolve the vertical structure in galactic disks, and horizontally large enough particles to suppress the vertical heating due to two-body effects.
Dalcanton, Julianne J.; Gunn, James E.
Heat transfer system
A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
McGuire, Joseph C. (Richland, WA)
A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
Not Available
Vertical vector face lift.
Facial rejuvenation using local anesthesia has evolved in the past decade as a safer option for patients seeking fewer complications and minimal downtime. Mini- and short-scar face lifts using more conservative incision lengths and extent of undermining can be effective in the younger patient with lower face laxity and minimal loose, elastotic neck skin. By incorporating both an anterior and posterior approach and using an incision length between the mini and more traditional face lift, the Vertical Vector Face Lift can achieve longer-lasting and natural results with lesser cost and risk. Submentoplasty and liposuction of the neck and jawline, fundamental components of the vertical vector face lift, act synergistically with superficial musculoaponeurotic system plication to reestablish a more youthful, sculpted cervicomental angle, even in patients with prominent jowls. Dramatic results can be achieved in the right patient by combining with other procedures such as injectable fillers, chin implants, laser resurfacing, or upper and lower blepharoplasties. PMID:21276163
Somoano, Brian; Chan, Joanna; Morganroth, Greg
A Study of the Vertical Transport of Momentum, Sensible Heat, and Water Vapor over Vegetation-Covered Surfaces in the Tropics Um Estudo DOS Transportes Verticais de Momentum, Calor Sensivele Vapor d'Agua Sobre Superficie Vegetada Nos Tropicos.
The energy balance changes with aerodynamic characteristics of the surface for four successive crop stage are presented. Parameterizations are used to calculate the sensible and water vapor fluxes. The results of the momentum, sensible heat and water vapo...
R. G. B. Andre
Vortex Formation in Vertically Stratified Protoplanetary Disks
A central problem of planet formation is how to form large planetesimals in a turbulent protoplanetary disk. Recent work suggests that MRI turbulence would excite such large velocities that the planetesimals would collisionally fragment rather than grow. The structure of chondritic meteorites indicates a gentle nebular environment where chondrules are sorted by size and cemented together rapidly. Although it is well established that anticyclones can concentrate particles that are weakly coupled to the gas in protoplanetary disks, the conditions required for the formation and long-time stability of anticyclones in a vertically stratified disk are still highly uncertain. Fully three dimensional fluid dynamic simulations of protoplanetary disks are computationally expensive when one requires a computational domain that is large compared to the vertical scale height of the disk. An alternative simulation approach is to use potential temperature as the vertical coordinate so that the equations of motion resemble the shallow water equations (Dowling et al. 1998). We have therefore modified a multilayer shallow water simulation code to model the formation of vortices in a vertically stratified protoplanetary disk with a radial entropy gradient. Vertical stratification of the disk is modeled by using multiple layers, where each layer has a different constant value of the entropy. By forcing a slope in the interfaces between the layers, we impose a radial entropy gradient in the disk. Radiative heating and cooling causes vertical mass exchange between adjacent constant entropy layers according to a Newton cooling formula. We find that the formation of anticyclones is robust, and that these vortices actively excite density waves, which in turn, transport angular momentum through the disk. Our simulations therefore yield new insights on how the dusty dead zones of protoplanetary disks can transport angular momentum through the disk by purely hydrodynamic processes. Support from NASA�s Origins of Solar Systems program is gratefully acknowledged.
Stewart, Glen R.
In previous study, the characteristic of the condensation heat transfer on the dispersed vertical surface were investigated experimentally for the application of the finned surface to the thermoelectric generator utilizing boiling and condensation as the electrodes of the thermoelectric module. A prediction model for this diapered finned surface was proposed, based on Adamek-Webb model of the condensation on a finned tube. In this study, a condensation heat transfer experiment on a vertical dispersed finned surfaces using FC5312 was carried out, in order to enhance the condensation heat transfer coefficient by optimizing the fin size on a dispersed heat transfer surface. Experimental parameters were the fin width, thickness, height and the dispersed fin length. As the results, it was found from the experiment there was a dispersed fin length corresponding to the condensation at the maximum and its value was 1.75 mm. As the characteristic, the condensation changed from slowly increasing to rapidly increasing and then decreasing at a steep grade, with decreasing the dispersed fin length. In addition, the fin height did not affect this optimum dispersed fin length and the dispersed fin length affects the dependence of the condensation on different fin thickness. Further, the prediction values have a good agreement with the experimental data except the case of short dispersed fin length.
Vertical blind assembly
US Patent & Trademark Office Database
A vertical blind assembly includes an elongate header casing and two sets of louvers movably supported in adjacent channels within the header casing, including a first set of plain louvers structured to be moved horizontally along the length of the first channel, and a second set of louvers which are molded and configured in a decorative, three-dimensional pattern and structured to be moved horizontally along the length of the second channel so that they are positioned in front of the first set of louvers.
'Endurance' Untouched (vertical)
Vertical Motion Simulator
The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.
Vertical velocity estimates in the North Pacific using Argo floats
Vertical velocity in the oceans is critical for maintenance of the structure of the main thermoclines and the transport of nutrients from deepwater towards the surface and thus is an important variable for understanding the dynamics of the ocean and the transport of scalar variables. In the mid 1970s the author was engaged in discussions with Tom Rossby about how SOFAR floats might be used to observe the vertical component of velocity. This paper in some sense follows on from those discussions almost 40 years later. In this paper the Argo array is used to compute the horizontal volume divergence in a control volume in the North Pacific. Divergence is found and this must be related to a volume flux through the base of the control volume. The implied vertical velocity is large and various tests are proposed to determine whether or not the estimate is plausible. The first test shows that a vertical velocity this large is necessary to close the salt budget. The second test shows that the vertical velocity balances about half of the observed heat divergence, the remainder is then accounted for by heat flux at the sea surface. Finally the time variable vertical velocity is computed and used to compute the evolution of the salt content in the control volume. Thus though the estimated vertical velocity is surprisingly large, it passes plausibility tests.
Freeland, Howard J.
Solar heating\\/cooling system
A solar heating and cooling system comprising a multi-tiered collector and heat exchanger is described that is mounted on a roof or installed in a vertical wall. Each tier of the exchanger includes a plurality of longitudinal channels with upper and lower manifolds communicating with all of the channels. A duct extends from each manifold into the premises being heated
Effects of random horizontal variations in radiogenic heat source distribution on its relationship with heat flow
Lateral conduction resulting from variations in the radiogenic heat generation is known to modify the heat flow-heat generation relation and to bias the evaluation of thickness of radiogenic heat sources. In this paper a statistical approach is used to account for a random horizontal variation in radiogenic heat sources, whereas their vertical variation is simulated by simple models. Relationships between
G. Vasseur; R. N. Singh
Vertical Dimension in Complete Dentures.
The video demonstrates proportional and functional methods to establish a tentative vertical dimension for the edentulous patient. It emphasizes the correlation of this dimension with the centric relation.
Waste heat recovery in asphalt mixing plant
In an asphalt mixing plant, a portion of the heat used to vaporize water in the process of drying aggregate is recovered by conducting dryer exhaust gases through parallel ducts which extend serially through the aggregate cold feed bins. These parallel ducts are vertically elongated for optimum heat transfer and to avoid impeding aggregated flow. The ducts have vertically extending
Vertical quantum dot with a vertically coupled charge detector
We fabricated a vertical quantum dot equipped with a charge detector. The dot current flows vertically between the top and bottom contacts. The charge detector is formed at the bottom contact layer with a current channel constricted to the region just under the dot. This channel current is reduced by addition of an extra electron onto the dot due to
Koichiro Zaitsu; Yosuke Kitamura; Keiji Ono; Seigo Tarucha
Natural convection in vertical Bridgman configurations
Buoyancy driven convection in closed vertical cylinders heated from below and crystal growth in corresponding configurations (vertical Bridgman technique with top seeding) have been studied experimentally and theoretically. The hydrodynamic state in such configurations is described by three dimensionless numbers, the Rayleigh number Ra, the aspect ratio (height h/diameter d) and the Prandtl number Pr. Two different types of melts have been investigated, H 2O (Pr = 6.7), and Ga and GaSb melts (Pr ? 2 � 10 -2) for various aspect ratios (0.5 ? h/ d ? 5) and Rayleigh numbers up to 10 8. Both experimental results and numerical analysis for the onset of convection (critical Rayleigh number Ra c1) and the state of convective flow are presented. The values of Ra c1 for 0.5 ? h/ d ? 5 and the symmetries of the basic flow (axial symmetry for h/ d = 0.5 and non-axial symmetry for 1 ? h/ d ? 5) are in good agreement with the theoretical predictions of Charlson and Sani [1]. Te-doped GaSb crystals have been grown by using the vertical Bridgman technique with top seeding. Temperatures have been measured in the GaSb melt during growth and compared with the results of our flow investigations in Ga melts. It shows clearly, that the occurrence of doping striations in the GaSb crystals can be very well correlated to the unsteady flow regimes.
M�ller, G.; Neumann, G.; Weber, W.
Measuring Growth with Vertical Scales
A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from�
Briggs, Derek C.
Vertical strabismus in monofixation syndrome
Purpose: The manifest angle of the horizontal deviation in monofixation syndrome (MFS) has been reported to reach a maximum of 8 to 10 PD. Review of the literature, however, revealed no studies about the vertical deviation associated with MFS. The purpose of this study is to evaluate the range of the angle of the vertical deviation in MFS. Methods: Forty
Dong Gyu Choi; Sherwin J. Isenberg
Functions and Vertical Line Test
This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.
The Gains from Vertical Scaling
It is often assumed that a vertical scale is necessary when value-added models depend upon the gain scores of students across two or more points in time. This article examines the conditions under which the scale transformations associated with the vertical scaling process would be expected to have a significant impact on normative interpretations�
Briggs, Derek C.; Domingue, Ben
Free convection in hydromagnetic flows in a vertical wavy channel
Free convection in hydromagnetic flows in a vertical wavy channel in the presence of a constant heat source or sink is investigated analytically. The zeroth-order, first-order, and total solutions to the problem are determined numerically for different values of the principal parameters using a mathematical method similar to that of Vajravelu and Sastri (1978). The velocity and temperature profiles are
D. R. V. P. Rao; D. V. Krishna; L. Debnath
Undamped inductive switching of integrated quasi-vertical DMOSFETs
This investigation explores the unclamped inductive switching (UIS) performance and failure mechanisms of 60 V quasi-vertical N-channel DMOSFETs through measurement and numerical device simulation. The non-uniform current distributions that arise inside the DMOS during UIS are analyzed and the effects of local self-heating are investigated
R. Constapel; M. S. Shekar; R. K. Williams
Warm vertical gutta-percha obturation: a technique update.
An updated version of the vertical warm gutta-percha obturation technique is presented. Recent research suggests that the physical properties of gutta-percha may be altered by using heat carriers that are too hot or by overheating gutta-percha in a flame. The technique proposes a simple method of thermoplasticizing and delivering gutta-percha without overheating it. PMID:8006575
Jerome, C E
We fabricated a vertical quantum dot equipped with a charge detector. The dot current flows vertically between the top and bottom contacts. The charge detector is formed at the bottom contact layer with a current channel constricted to the region just under the dot. This channel current is reduced by addition of an extra electron onto the dot due to the electrostatic coupling to the dot. The charge state of the vertical dot was detected, starting from zero electrons. The sensitivity of the charge detector was comparable to that previously reported for lateral dots with nearby quantum point contacts.
Zaitsu, Koichiro; Kitamura, Yosuke; Ono, Keiji; Tarucha, Seigo
A new contribution to the finite line-source model for geothermal boreholes
Heat transfer around vertical ground heat exchangers is a common problem for the design and simulation of ground-coupled heat pump (GCHP) systems. Most models are based on step response of the heat transfer rate, and the superposition principle allows the final solution to be in the form of the convolution of these contributions. The step response is thus a very
Numerical computation of magnetothermal convection of water in a vertical cylindrical enclosure
Numerical computations were carried out to clarify the effect of Kelvin force on the flow of water in a vertical cylindrical enclosure heated from below and cooled from above under a vertical magnetic field gradient. Since the Kelvin force that is produced by the magnetic field gradient depends on the position and the size of a circular electric coil, the
Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe
The Effect of Vertical Shear on Tropical Cyclone Intensity Change.
The effect of vertical shear on tropical cyclone intensity change is usually explained in terms of `ventilation' where heat and moisture at upper levels are advected away from the low-level circulation, which inhibits development. A simple two-layer diagnostic balance model is used to provide an alternate explanation of the effect of shear. When the upper-layer wind in the vortex environment differs from that in the lower layer, the potential vorticity (PV) pattern associated with the vortex circulation becomes tilted in the vertical. The balanced mass field associated with the tilted PV pattern requires an increased midlevel temperature perturbation near the vortex center. It is hypothesized that this midlevel warming reduces the convective activity and inhibits the storm development.Previous studies have shown that diabatic heating near the storm center acts to reduce the vertical tilt of the vortex circulation. These studies have also shown that there is an adiabatic process that acts to reduce the vertical tilt of a vortex. The effectiveness of the adiabatic process depends on the Rossby penetration depth, which increases with latitude, horizontal scale, and vortex amplitude. Large-scale analyses from the 1989-1994 Atlantic hurricane seasons are used to show that high-latitude, large. and intense tropical cyclones tend to be less sensitive to the effect of vertical shear than low-latitude, small, and weak storms.
Demaria, Mark
Horizontal and Vertical Line Designs.
Presents an art lesson in which students learn about the artist Piet Mondrian and create their own abstract artworks. Focuses on geometric shapes using horizontal and vertical lines. Includes background information about the artist. (CMK)
Johns, Pat
Vertical Electromagnetic Pulse (VEMP) Testing.
This TOP provides methods for planning, providing instrumentation, and execution of testing of Army/DOD Materiel to determine the effects of Vertical Component High Altitude Electromagnetic Pulse (VHEMP) Environment on the safety and/or reliability of the...
Vertical axis wind turbine airfoil
A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.
Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich
Vertical Reactor Coolant Pump Instabilities.
This paper describes the investigation conducted at the Tennessee Valley Authority's Sequoyah Nuclear Power Plant to determine and correct increasing vibrations in the vertical reactor coolant pumps. Diagnostic procedures to determine the vibration causes...
Horizontal Inequity and Vertical Redistribution
Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by
Peter J. Lambert; Xavier Ramos
Analogy between steam condensation on a horizontal tube bundle and on a vertical wall
Experimental results are given for heat transfer with low-pressure steam condensation on the tubes of a test model of a condenser represented by a vertical row of 16 horizontal tubes. The correlation of the results is made assuming an analogy between steam condensation on a vertical wall and on the horizontal tube bundle. Computational relations are suggested for determining the heat transfer coefficient on the steam side for different zones of the condenser.
Arkhipov, G.A.; Volkov, D.I.; Makarov, O.I.; Chistyakov, V.A
Solar heat regulator
A solar heat regulating device selectively heats, with sunlight, the air in a building having a window therein and alternately shields and insulates the air in the building from the heat of sunlight. A frame is provided for mounting the solar heat regulating device inside the structure adjacent to the window. A plurality of hollow vanes each of which have a passageway therethrough. Each of the vanes has a heat absorptive surface on one side which allows solar radiation impinging thereon to heat the air in the passageways of the vanes. The vanes also have a heat reflective surface on another side. The heat reflective surface reflects the solar radiation impinging thereon and insulates the air inside the building from the heat of the sunlight. The vanes are rotatably mounted about vertical axes and spaced so that either the heat absorptive surfaces on the vanes or the heat reflective surfaces on the vanes may face the outside of the building. The device includes means for sealing the outside facing surfaces of the vanes from the inside of the building. Manifold means are also provided for conducting the cooler air from the inside of the building to the bottom of the passageways in the vanes and for conducting the heated air from the top of the passageways of the vanes to the inside of the building.
Heat-pipe Earth.
The heat transport and lithospheric dynamics of early Earth are currently explained by plate tectonic and vertical tectonic models, but these do not offer a global synthesis consistent with the geologic record. Here we use numerical simulations and comparison with the geologic record to explore a heat-pipe model in which volcanism dominates surface heat transport. These simulations indicate that a cold and thick lithosphere developed as a result of frequent volcanic eruptions that advected surface materials downwards. Declining heat sources over time led to an abrupt transition to plate tectonics. Consistent with model predictions, the geologic record shows rapid volcanic resurfacing, contractional deformation, a low geothermal gradient across the bulk of the lithosphere and a rapid decrease in heat-pipe volcanism after initiation of plate tectonics. The heat-pipe Earth model therefore offers a coherent geodynamic framework in which to explore the evolution of our planet before the onset of plate tectonics. PMID:24067709
Moore, William B; Webb, A Alexander G
Vertical Slot Convection: A linear study
The linear stability properties of fluid convection in a vertical slot were studied. We use a Fourier-Chebychev decomposition was used to set up the linear eigenvalue problems for the Vertical Slot Convection and Benard problems. The eigenvalues, neutral stability curves, and critical point values of the Grashof number, G, and the wavenumber were determined. Plots of the real and imaginary parts of the eigenvalues as functions of G and [alpha] are given for a wide range of the Prandtl number, Pr, and special note is made of the complex mode that becomes linearly unstable above Pr [approximately] 12.5. A discussion comparing different special cases facilitates the physical understanding of the VSC equations, especially the interaction of the shear-flow and buoyancy induced physics. Making use of the real and imaginary eigenvalues and the phase properties of the eigenmodes, the eigenmodes were characterized. One finds that the mode structure becomes progressively simpler with increasing Pr, with the greatest complexity in the mid ranges where the terms in the heat equation are of roughly the same size.
McAllister, A. (Tokyo Univ. (Japan)); Steinolfson, R. (Southwest Research Inst., San Antonio, TX (United States)); Tajima, T. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies)
The linear stability properties of fluid convection in a vertical slot were studied. We use a Fourier-Chebychev decomposition was used to set up the linear eigenvalue problems for the Vertical Slot Convection and Benard problems. The eigenvalues, neutral stability curves, and critical point values of the Grashof number, G, and the wavenumber were determined. Plots of the real and imaginary parts of the eigenvalues as functions of G and {alpha} are given for a wide range of the Prandtl number, Pr, and special note is made of the complex mode that becomes linearly unstable above Pr {approximately} 12.5. A discussion comparing different special cases facilitates the physical understanding of the VSC equations, especially the interaction of the shear-flow and buoyancy induced physics. Making use of the real and imaginary eigenvalues and the phase properties of the eigenmodes, the eigenmodes were characterized. One finds that the mode structure becomes progressively simpler with increasing Pr, with the greatest complexity in the mid ranges where the terms in the heat equation are of roughly the same size.
McAllister, A. [Tokyo Univ. (Japan); Steinolfson, R. [Southwest Research Inst., San Antonio, TX (United States); Tajima, T. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies
Convective flows in enclosures with vertical temperature or concentration gradients
The transport process in the fluid phase during the growth of a crystal has a profound influence on the structure and quality of the solid phase. In vertical growth techniques the fluid phase is often subjected to vertical temperature and concentration gradients. The main objective is to obtain more experimental data on convective flows in enclosures with vertical temperature or concentration gradients. Among actual crystal systems the parameters vary widely. The parametric ranges studied for mass transfer are mainly dictated by the electrochemical system employed to impose concentration gradients. Temperature or concentration difference are maintained between two horizontal end walls. The other walls are kept insulated. Experimental measurements and observations were made of the heat transfer or mass transfer, flow patterns, and the mean and fluctuating temperature distribution. The method used to visualize the flow pattern in the thermal cases is an electrochemical pH-indicator method. Laser shadowgraphs are employed to visualize flow patterns in the solutal cases.
Wang, L. W.; Chai, A. T.; Sun, D. J.
Vertically transmitted symbiont reduces host fitness along temperature gradient.
Parasites with exclusive vertical transmission from host parent to offspring are an evolutionary puzzle. With parasite fitness entirely linked to host reproduction, any fitness cost for infected hosts risks their selective elimination. Environmental conditions likely influence parasite impact and thereby the success of purely vertical transmission strategies. We tested for temperature-dependent virulence of Caedibacter taeniospiralis, a vertically transmitted bacterial symbiont of the protozoan Paramecium tetraurelia. We compared growth of infected and cured host populations at five temperatures (16�32 �C). Infection reduced host density at all temperatures, with a peak of ?30% at 28 �C. These patterns were largely consistent across five infected Paramecium strains. Similar to Wolbachia symbionts, C. taeniospiralis may compensate fitness costs by conferring to the host a �killer trait�, targeting uninfected competitors. Considerable loss of infection at 32 �C suggests that killer efficacy is not universal and that limited heat tolerance restricts the conditions for persistence of C. taeniospiralis. PMID:24779056
Dusi, E; Krenek, S; Schrallhammer, M; Sachse, R; Rauch, G; Kaltz, O; Berendonk, T U
Vertical motion simulator familiarization guide
The Vertical Motion Simulator Familiarization Guide provides a synoptic description of the Vertical Motion Simulator (VMS) and descriptions of the various simulation components and systems. The intended audience is the community of scientists and engineers who employ the VMS for research and development. The concept of a research simulator system is introduced and the building block nature of the VMS is emphasized. Individual sections describe all the hardware elements in terms of general properties and capabilities. Also included are an example of a typical VMS simulation which graphically illustrates the composition of the system and shows the signal flow among the elements and a glossary of specialized terms, abbreviations, and acronyms.
Danek, George L.
Convection in vertical Bridgman configurations
We are interested in tracing the convective profiles of vertical Bridgman growth in two configurations, the pure Rayleigh convective mode and the combined Rayleigh-Marangoni mode. In order to do so, we conducted a numerical investigation that involved a finite volume calculation. The governing equations were integrated about a cell volume, using the Gauss Theorem and the volume variables like temperature and velocity were related to the surface variables. In order to solve for the pressure field, we employed the continuity equation and the residuals resulted in a Poisson equation. Results and comments for the Rayleigh and Marangoni problems in a vertical cylinder or Bridgman configuration are given.
Narayanan, Ranga
Natural convection of two staggered cylinders for various prandtl numbers and vertical and horizontal pitches
Natural convection heat transfer phenomena of two staggered cylinders were investigated for laminar flows. Numerical simulations were carried out to examine the effect of varying the Prandtl number and the vertical and horizontal pitch-to-diameter ratios for a Rayleigh number of 1.5 � 108 using FLUENT. This study focused on phenomena related to very small vertical pitch. The heat transfer rates of the upper cylinders were influenced by plumes from the lower cylinders, exhibiting preheating, velocity, sweep, and side flow effects. The heat transfer rates of the lower cylinders were not affected by the upper cylinders at moderate vertical pitches. However, when the vertical pitch was very small, they were affected by stagnant flow, sweep, and side flow effects.
Heo, Jeong-Hwan; Chung, Bum-Jin
Investigation of Factors Affecting Vertical Drain Behavior
Some influencing factors on vertical drain behavior were investigated by laboratory tests as well as by back-analyses of test embankments on vertical drain improved subsoil at Saga Airport, Saga, Japan. Based on the results from this study, suggestions are made on determining the design parameters for vertical drain improvement. For the discharge capacity test of a prefabricated vertical drain, confining
Jun-Chun Chai; Norihiko Miura
A FORTRAN computer program called GROCS (GRound Coupled Systems) has been developed to study 3-dimensional underground heat flow. Features include the use of up to 30 finite elements or blocks of Earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth dependent boundary conditions. No explicit consideration of mositure movement or freezing is given. GROCS has been used to model the thermal behavior of buried solar heat storage tanks (with and without insulation) and serpentine pipe fields for solar heat pump space conditioning systems. The program is available independently or in a form compatible with specially written TRNSYS component TYPE subroutines. The approach taken in the design of GROCS, the mathematics contained and the program architecture, are described. Then, the operation of the stand-alone version is explained. Finally, the validity of GROCS is discussed.
Natural convection between a vertical cylinder and a surrounding array
The generic situation considered is natural convection between a single heated, vertical cylinder and a surrounding array of cooler vertical cylinders in a triangular pattern. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6 by adjusting the electrical power. The Rayleigh number, based on test section diameter and air properties evaluated at cooling tube temperature, ranged from 2.9 x 10{sup 4} to 4.6 x 10{sup 5}. Results indicate that the convective heat transfer data could be approximated as Nu{sub D} (T{sub ts}/T{sub ct}){sup 0.14} = 0.156 Ra{sub D}{sup 1/3} in the apparent turbulent region for Ra{sub L} > 1.2 x 10{sup 11.}
McEligot, D.M.; O'Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.
McEligot, D.M.; O`Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.
Scale Shrinkage in Vertical Equating
As an alternative to equipercentile equating in the area of multilevel achievement test batteries, item response theory (IRT) vertical equating has produced unexpected results. When expanded standard scores were obtained to link the Comprehensive Test of Basic Skills and the California Achievement Test, the variance of test scores diminished both within particular grade levels from fall to spring, and also
Gregory Camilli; Kentaro Yamamoto; Ming-mei Wang
Vertically Fused Face Sheet Performance.
This study evaluates the performance of vertically fused face sheet mirrors used in adaptive optical systems that are subjected to high thermal irradiance. A one meter diameter by 20mm thick segmented, low expansion glass face sheet was fabricated from di...
H. M. Simmons J. W. Pepi
Graphs with four boundary vertices
A vertex v of a graph G is a boundary vertex if there exists a vertex u such that the distance in G from u to v is at least the distance from u to any neighbour of v. We give a full description of all graphs that have exactly four boundary vertices, which answers a question of Hasegawa and
Tobias M�ller; A. Por; J.-S. Sereni
Vertical Instability in KEK Booster
In the KEK Booster Synchrotron, from one msec after injection to extraction timing, beam intensity is stable, though it is reduced to about one half during one msec after injection. An instability of the vertical direction is one of the candidates of the beam loss. The e-folding time of the instability is less than 0.1 msec, and it strongly depends
M. Suetake; T. Kasuga; T. Kawakubo; I. Sakai; H. Someya; S. Takeda
Vertical Pricing and Parallel Imports
We generalize an earlier model of international vertical pricing to explain key features of parallel imports, or unauthorized trade in legitimate goods. When a manufacturer (or trademark owner) sells its product through an independent agent in one country, the agent may find it profitable to engage in parallel trade, selling the product to another country without the authorization of the
Yongmin Chen; KEITH E. MASKUS
Vertical Instability at IPNS RCS.
The rapid cycling synchrotron (RCS) of the intense pulsed neutron source (IPNS) at ANL accelerates > 3.0 times 10{sup 12} protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, large- amplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1]. More data analysis and experiments were performed to characterize the instability.
Wang, S.; Brumwell, F. R.; Dooling, J. C.; Harkay, K. C.; Kustom, R.; McMichael, G. E.; Middendorf, M. E.; Nassiri, A.; Accelerator Systems Division (APS)
Ground-source Heat Pumps Applied to Commercial Buildings
Ground-source heat pumps can provide an energy-efficient, cost-effective way to heat and cool commercial facilities. While ground-source heat pumps are well established in the residential sector, their application in larger, commercial-style, facilities is lagging, in part because of a lack of experience with the technology by those in decision-making positions. Through the use of a ground-coupling system, a conventional water-source heat pump design is transformed to a unique means of utilizing thermodynamic properties of earth and groundwater for efficient operation throughout the year in most climates. In essence, the ground (or groundwater) serves as a heat source during winter operation and a heat sink for summer cooling. Many varieties in design are available, so the technology can be adapted to almost any site. Ground-source heat pump systems can be used widely in commercial-building applications and, with proper installation, offer great potential for the commercial sector, where increased efficiency and reduced heating and cooling costs are important. Ground-source heat pump systems require less refrigerant than conventional air-source heat pumps or air-conditioning systems, with the exception of direct-expansion-type ground-source heat pump systems. This chapter provides information and procedures that an energy manager can use to evaluate most ground-source heat pump applications. Ground-source heat pump operation, system types, design variations, energy savings, and other benefits are explained. Guidelines are provided for appropriate application and installation. Two case studies are presented to give the reader a sense of the actual costs and energy savings. A list of manufacturers and references for further reading are included for prospective users who have specific or highly technical questions not fully addressed in this chapter. Sample case spreadsheets are provided in Appendix A. Additional appendixes provide other information on the ground-source heat pump technology.
Parker, Steven A.; Hadley, Donald L.
Laminar natural convection along vertical corners and rectangular channels
Laminar natural convection along a vertical right angle corner and in rectangular ducts has been analyzed. Solutions for isothermal and constant heat flux walls have been obtained by a coupled strongly implicit procedure. The effect of Prandtl number on the corner flow behavior is examined. It is also shown that rectangular ducts entrain a larger amount of mass than do square ducts of equal length.
Ramakrishna, K.; Khosla, P. K.; Rubin, S. G.
The Effect of Vertical Shear on Tropical Cyclone Intensity Change
The effect of vertical shear on tropical cyclone intensity change is usually explained in terms of `ventilation' where heat and moisture at upper levels are advected away from the low-level circulation, which inhibits development. A simple two-layer diagnostic balance model is used to provide an alternate explanation of the effect of shear. When the upper-layer wind in the vortex environment
Mark Demaria
On the Vertical Thermal Structure of Pluto's Atmosphere
A radiative�conductive model for the vertical thermal structure of Pluto's atmosphere is developed with a non-LTE treatment of solar heating in the CH43.3 ?m and 2.3 ?m bands, non-LTE radiative exchange and cooling in the CH47.6 ?m band, and LTE cooling by CO rotational line emission. The model includes the effects of opacity and vibrational energy transfer in the CH4molecule.
Darrell F. Strobel; Xun Zhu; Michael E. Summers; Michael H. Stevens
Heating with waste heat
Most of the power consumed in the gaseous diffusion process is converted into heat of compression, which is removed from the process gas and rejected into the atmosphere by recirculating cooling water over cooling towers. The water being handled through the X-333 and X-330 Process Buildings can be heated to 140 to 150/sup 0/F for heating use. The Gas Centrifuge Enrichment Plant is provided with a recirculating heating water (RHW) system which uses X-330 water and wasted heat. The RHW flow is diagrammed. (DLC)
Beabout, R.W.
Transient or steady-state? Using vertical temperature profiles to quantify groundwater-surface water exchange
Heat is recognized as a natural tracer to identify the exchange of water between the groundwater and surface water compartment. One-dimensional (1D) heat transport models have the ability to obtain quantitative estimates of vertical fluxes through the sediment matrix. Input to these models can come from temperatures observed in the surface water and in the bed material of rivers and
Christian Anibas; Jan H. Fleckenstein; Nina Volze; Kerst Buis; Ronny Verhoeven; Patrick Meire; Okke Batelaan
Investigation of the Vertical Bunsen Burner Test for Flammability of Plastics.
A vertical Bunsen burner test for flammability of plastics (UL-94V) was studied in an attempt to relate the upward burning of plastics to their material fire properties. It was shown that the heat release parameter, the critical heat flux for piloted igni...
B. P. Downey J. G. Quintiere R. E. Lyon
If water is heated or cooled while flowing through a vertical pipe with ; a laminar motion, the velocity profile will differ from the parabolic shape for ; isothermal flow due to density variations in the fluid. If a constant heat flux ; is used at the wall and if the changes in temperature affect only the density ; appearing
George F. Scheele; Thomas J. Hanratty
Adjustment to heating, potential vorticity and cyclogenesis
Solutions of an isentropic coordinate model of the atmosphere, permitting acoustic waves and inertial gravity waves, demonstrate that a vertically symmetric heat source in the troposphere usually induces a vertically asymmetric dipole anomaly in the potential vorticity (PV), with an intense, tall and thin positive (cyclonic) anomaly below a less intense, flat and broad negative (anticyclonic) anomaly. The emergence of this asymmetry is associated with the vertical gradient of the PV,which is an important factor in the local PV budget, even when this gradient is zero initially. The degree of vertical asymmetry of the response to heating depends on the 'thickness' (in K) of the heated layer relative to the total heat added. The adjusted balanced state shows little sensitivity to the heating intensity (i.e. the time-scale within which the heat is added), in spite of the existence of large-amplitude waves when the heating is applied very abruptly relative to the adiabatic adjustment time-scale. The surrounding (non-heated) region shows little permanent change due to the process of adjustment as far as PV substance and mass is concerned, and only functions as a transmitter of acoustic waves and inertial gravity waves. The balanced state is sensitive to variations in the horizontal scale of the heat source. The response to heating within a PV stratified region (for example, in the region of the tropopause) is quite subtle. For example, it is shown that a heat source in the tropopause region induces a predominantly anticyclonic wind anomaly.
van Delden, Aarnout
Vertical formations demand unique treatments
In the US midcontinent area, major thrust faults trap large quantities of hydrocarbons in the down-thrown fault block. As exploration of these thrust fault structures continues, the application of extended reach and horizontal well bores will increase. Formations in deep structures are apt to have lower porosity and permeability than the currently developed thrust faults and thus, require fracture stimulation. In addition, the portion of the formation closest to the fault may be subjected to folding resulting in a vertical formation penetrated by a horizontal well bore. Low porosity and vertical bedding were encountered in the City of Lawton No. 1-34, an 18,088-ft wildcat (14,627-ft TVD) in Caddo County, Oklahoma. This article details methods to overcome the obstacles that well bore and formation geometry present to fracture stimulation operations in the 17,714-ft (14,614-ft TVD) Britt sand.
Fairchild, K. [Fina Oil and Chemical Co., Midland, TX (United States)
Kinematic Fitting of Detached Vertices
The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.
Paul Mattione
Geometry effects on critical heat flux for subcooled convective boiling from an array of heated elements
The critical heat flux (CHF) condition was experimentally determined for subcooled flow boiling from an array of simulated microelectronic devices on one wall of a vertical rectangular passage. A test apparatus was used in these experiments that allowed visual observation of the boiling process while simultaneously measuring the heat flux and surface temperature for ten heat-dissipating elements. Using R-113 as
W. R. McGillis; V. P. Carey; B. D. Strom
Vertical Structure of the Atmosphere
Earth is surrounded by a protective atmosphere, composed of nitrogen, oxygen, and argon, and trace amounts of other gases, that protects Earth's surface from damaging solar radiation and plays a major role in water and energy transport. This interactive feature shows the vertical structure of the atmosphere. Viewers can see the regions of the atmosphere, some of the objects (natural and man-made) found at various altitudes, as well as the variations in air temperature and pressure with altitude.
NASA-Ames vertical gun
A national facility, the NASA-Ames vertical gun range (AVGR) has an excellent reputation for revealing fundamental aspects of impact cratering that provide important constraints for planetary processes. The current logistics in accessing the AVGR, some of the past and ongoing experimental programs and their relevance, and the future role of this facility in planetary studies are reviewed. Publications resulting from experiments with the gun (1979 to 1984) are listed as well as the researchers and subjects studied.
Schultz, P. H.
Understanding basics of vertical pumps
Discusses requirements of vertical centrifugal pumps for slurry service. Points out that the most commonly accepted criterion for the classification of a pump for a slurry application is wear adjustment. Presents graph showing the relative effect of radial thrust at other than best efficiency conditions. Diagram illustrates how radial thrust problems can be reduced by using a double volute. Examines the use of alloys, protective coatings (e.g. rubber or synthetic elastomers), and cast ceramics for corrosion and abrasion resistance.
Haentjens, W.D.
Tropical Cyclone Intensity in Vertical Wind Shear.
The structure and intensity changes of tropical cyclones (TCs) in environmental vertical wind shear (VWS) are investigated in this study using the fifth-generation Pennsylvania State University National Center for Atmospheric Research (PSU NCAR) Mesoscale Model (MM5). Triply nested domains of 36-, 12-, and 4-km resolution are used with fully explicit moisture physics in the 4-km domain. Idealized environments with easterly shears of 2, 4, 6, 8, and 10 m s-1 between 800 and 200 hPa are applied on an f plane. Under small values of VWS (2 and 4 m s-1), the TC intensities are similar to that of the control (CTRL; i.e., no VWS) after initial adjustments. The TCs under 6 and 8 m s-1 of VWS are not as intense, although they do not weaken during the simulation. On the other hand, the TC in 10 m s-1 of VWS weakened significantly.Given the same VWS, the TC intensity is also found to be sensitive to TC size. Experiments with TCs with a smaller radius of 15 m s-1 wind reveal that while the TC in 2 m s-1 of VWS remains as intense as the CTRL, the TC in the 4 m s-1 VWS case weakened significantly to a minimal hurricane by the end of the simulation. A VWS of 6 m s-1 is strong enough to cause dissipation of the TC in 72 h. These results indicate that the size of a TC has to be taken into account in determining the intensity change of a TC in VWS.In the 10 m s-1 VWS case, the average temperature over the lower half of the troposphere within 50 km from the TC surface center is higher than that of the CTRL throughout the simulation. Such a warming, though of a small magnitude, is also observed for a brief period in the upper half of the troposphere before the rapid weakening of the TC and is related to the asymmetry of temperature required for a tilt of the vortex axis. The evolution of the vortex tilt is found to be similar to the dry simulations in previous studies, with the midlevel center (? = 0.525) located mainly in the southeast quadrant of the surface center. A tendency for the midlevel center to rotate about the surface center is also observed. These results support the idea that the resistance to vertical tilt by the mutual rotation between the low-level and midlevel centers is also valid in the moist simulations.It is hypothesized that the secondary circulation and the associated diabatic heating reduce the vertical tilt and the weakening. Condensation heating offsets the anomalous cooling effect due to the anomalous rising motion ahead of the vortex tilt. For small VWS, the vertical motion asymmetry is not strong enough to destroy the complete secondary circulation and the eyewall. As a result, a large temperature asymmetry and the associated vortex tilt cannot develop. Furthermore, there is no entrainment of cool/dry air in the upper troposphere. Therefore, TCs under small shears can be as intense as the CTRL.Large-scale asymmetries in the form of anticyclones found in previous studies are also observed. These asymmetries are apparently related to the change of shears near the TCs. While the shears at outer radii stay roughly constant with time, the shears near the TC centers can have large temporal fluctuations both in magnitude and orientation. This result suggests that the location at which the VWS is estimated in observational studies could be important in determining the relationship between VWS and TC intensity change.
Wong, Martin L. M.; Chan, Johnny C. L.
5-Foot Vertical Wind Tunnel
Construction of 5-Foot Vertical Wind Tunnel. The 5-Foot Vertical Wind Tunnel was built to study spinning characteristics of aircraft. It was an open throat tunnel capable of a maximum speed of 80 mph. NACA engineer Charles H. Zimmerman designed the tunnel starting in 1928. Construction was completed in December 1929. It was one of two tunnels which replaced the original Atmospheric Wind Tunnel (The other was the 7x10-Foot Wind Tunnel.). In NACA TR 387 (p. 499), Carl Wenzinger and Thomas Harris report that 'the tunnel passages are constructed of 1/8-inch sheet iron, stiffened with angle iron and bolted together at the corners. The over-all dimensions are: Height 31 feet 2 inches; length, 20 feet 3 inches; width, 10 feet 3 inches.' The tunnel was partially constructed in the Langley hanger as indicated by the aircraft in the background. Published in NACA TR 387, 'The Vertical Wind Tunnel of the National Advisory Committee for Aeronautics,' by Carl J. Wenzinger and Thomas A. Harris, 1931.
Vertical Height of the Atmosphere
This is a lesson about the vertical dimension of the atmosphere and includes four activities. Activity 1 Introduces concepts related to distance, including length and height and units of measurement. Students are asked to make comparisons of distances. In activity 2, students learn about the vertical profile of the atmosphere. They work with a graph and plot the heights of objects and the layers of the atmosphere: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In activity 3, students learn about other forms of visual displays using satellite imagery. They compare images of the same weather feature, a hurricane, using two different images from MODIS and CALIPSO. One image is looking down on the hurricane from space, the other looks through the hurricane to display a profile of the hurricane. Activity 4 reinforces the concept of the vertical nature of the atmosphere. Students will take a CALIPSO satellite image that shows a profile of the atmosphere and use this information to plot mountains and clouds on their own graph of the atmosphere. The recommended order for the activities is to complete the first two activities on day one, and the second two activities on day two. Each day will require approximately 1 to 1.5 hours.
Galactic Spiral Shocks with Thermal Instability in Vertically Stratified Disks
Galactic spiral shocks are dominant morphological features and believed to be responsible for substructure formation of spiral arms in disk galaxies. They can also provide a large amount of kinetic energy for the interstellar gas by tapping the rotational energy. We use numerical hydrodynamic simulations to investigate dynamics and structure of spiral shocks with thermal instability in vertically stratified galactic disks. We initially consider an isothermal disk in vertical hydrostatic equilibrium and let it evolve under interstellar cooling and heating. Due to cooling and heating, the disk rapidly turns to a dense slab near the midplane surrounded by rarefied gas at high-altitude regions. The imposed stellar spiral potential develops a vertically curved shock that exhibits strong flapping motions along the direction perpendicular to the arm. The flows across the spiral shock are characterized by transitions from rarefied to dense phases at the shock and from dense to rarefied phases at the postshock expansion zone. The shock flapping motions stirs the disk, supplying the gas with random kinetic energy. For a model resembling the galactic disk near the solar neighborhood, the density-weighted vertical velocity dispersions are 2 km/s for the rarefied gas and 1 km/s for the dense gas. The shock compression in this model reduces an amount of the rarefied gas from 29% to 19% by mass. Despite the flapping motions, the time-averaged profiles of surface density are similar to those of the one-dimensional counterparts, and the vertical density distribution is overall consistent with effective hydrostatic equilibrium. When self-gravity is included, the shock compression forms large gravitationally bound condensations with virial ratio of about 2 and typical masses of 0.5 to one million solar masses, comparable to the Jeans mass.
Kim, Chang-Goo; Kim, W.; Ostriker, E. C.
Evolution of the upper ocean layer during daytime heating
A one-dimensional model for the evolution of a near-surface layer during daytime heating is suggested. The paper considers how upward thermal fluxes and the Coriolis force affect the heated layer's vertical structure. Experiments have shown that atmospheric heat and impulse are localized in the heated layer, and that the earth's rotation causes deviation of the surface current velocity and reduction
V. N. Kudryavtsev; A. V. Tsvetkov
Metrics of hurricane-ocean interaction: vertically-integrated or vertically-averaged ocean temperature?
The ocean thermal field is often represented in hurricane-ocean interaction by a metric termed the upper Ocean Heat Content (OHC), the vertical integral of ocean temperature in excess of 26�C. High values of OHC have proven useful for identifying ocean regions that are especially favorable for hurricane intensification. Nevertheless, it is argued here that a more direct and robust metric of the ocean thermal field may be afforded by a vertical average of temperature, in one version from the surface to 100 m, a typical depth of vertical mixing by a mature hurricane. OHC and the depth-averaged temperature, dubbed T100, are well correlated over the deep open ocean in the high range of OHC, OHC?75 kJ cm-2. They are poorly correlated in the low range of OHC, ?50 kJ cm-2, in part because OHC is degenerate when evaluated on cool ocean temperatures ?26�C. OHC and T100 can be qualitatively different also over shallow continental shelves: OHC will generally indicate comparatively low values regardless of the ocean temperature, while T100 will take on high values over a shelf that is warm and upwelling neutral or negative, since there will be little cool water that could be mixed into the surface layer. Some limited evidence is that continental shelves may be regions of comparatively small sea surface cooling during a hurricane passage, but more research is clearly required on this important issue.
Price, J. F.
Mathematical simulation of lithium bromide solution laminar falling film evaporation in vertical tube
For utilization of the residual heat of flue gas to drive the absorption chillers, a lithium-bromide falling film in vertical tube type generator is presented. A mathematical model was developed to simulate the heat and mass coupled problem of laminar falling film evaporation in vertical tube. In the model, the factor of mass transfer was taken into account in heat transfer performance calculation. The temperature and concentration fields were calculated. Some tests were conducted for the factors such as Re number, heating flux, the inlet concentration and operating pressure which can affect the heat and mass transfer performance in laminar falling film evaporation. The heat transfer performance is enhanced with the increasing of heat flux. An increasing inlet concentration can weaken the heat transfer performance. The operating pressure hardly affects on heat and mass transfer. The bigger inlet Re number means weaker heat transfer effects and stronger mass transfer. The mass transfer obviously restrains the heat transfer in the falling film solution. The relation between dimensionless heat transfer coefficient and the inlet Re number is obtained.
Shi, Chengming; Wang, Yang; Hu, Huili; Yang, Ying
Internally baffled, horizontal flow, vertical oil skimmer
An internally baffled, horizontal flow, vertical oil separator or skimmer for the flotation and removal of oil from mixtures of oil and water has internal baffles that compel horizontal flow of a vertically elongated cross-section of fluid in the vertical vessel. The skimmer is of particular utility on offshore platforms where deck space is extremely expensive and limited.
Warne, J.P.
Vertical partitioning algorithms for database design
This paper addresses the vertical partitioning of a set of logical records or a relation into fragments. The rationale behind vertical partitioning is to produce fragments, groups of attribute columns, that �closely match� the requirements of transactions.Vertical partitioning is applied in three contexts: a database stored on devices of a single type, a database stored in different memory levels, and
Shamkant B. Navathe; Stefano Ceri; Gio Wiederhold; Jinglie Dou
On Vertical Mergers and Their Competitive Effects
It is well known that vertical integration cats change the pricing incentive of an upstream producer. However, it has not been noticed that vertical integration may also change the pricing incentive of downstream producer and the incentive of a competitor in choosing input suppliers. I develop an equilibrium theory of vertical merger that incorporates these additional strategic considerations. Under fairly
Vertical Lift - Not Just For Terrestrial Flight
Autonomous vertical lift vehicles hold considerable potential for supporting planetary science and exploration missions. This paper discusses several technical aspects of vertical lift planetary aerial vehicles in general, and specifically addresses technical challenges and work to date examining notional vertical lift vehicles for Mars, Titan, and Venus exploration.
Young, Larry A
Laser tracking for vertical control
The Global Laser Tracking Network has provided LAGEOS ranging data of high accuracy since the first MERIT campaign in late 1983 and we can now resolve centimeter-level three dimensional positions of participating observatories at monthly intervals. In this analysis, the station height estimates have been considered separately from the horizontal components, and can be determined by the strongest stations with a formal standard error of 2 mm using eight years of continuous observations. The rate of change in the vertical can be resolved to a few mm/year, which is at the expected level of several geophysical effects. In comparing the behavior of the stations to that predicted by recent models of post-glacial rebound, we find no correlation in this very small effect. Particular attention must be applied to data and survey quality control when measuring the vertical component, and the survey observations are critical components of the geodynamic results. Seasonal patterns are observed in the heights of most stations, and the possibility of secular motion at the level of several millimeters per year cannot be excluded. Any such motion must be considered in the interpretation of horizontal inter-site measurements, and can help to identify mechanisms which can cause variations which occur linearly with time, seasonally, or abruptly.
Dunn, Peter; Torrence, Mark; Pavlis, Erricos; Kolenkiewicz, Ron; Smith, David
Auroral heating and the composition of the neutral atmosphere.
Heating of the neutral atmosphere by auroral particle fluxes and by orthogonal electric fields is responsible for large changes in the thermospheric composition that have been observed by satellite mass spectrometers. Vertical winds of a few meters per second are produced in the region subject to auroral heating; this vertical upwelling drives circulation cells that extend the effects of heating in the auroral region on a global scale. Our analysis focuses on the initial phase of a magnetic storm within the auroral region.
Hays, P. B.; Jones, R. A.; Rees, M. H.
Fast reactor power plant design having heat pipe heat exchanger
The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.
Huebotter, Paul R. (Western Springs, IL); McLennan, George A. (Downers Grove, IL)
Huebotter, P.R.; McLennan, G.A.
The gamma heat generations in selected positions of the ETR were ; measured with aluminum calorimeters and graphite- CO�, ion chambers. ; Midplane gamma heat generation maps are presented for two fuel loadings along ; with vertical traverses for selected positions. Descriptions of the measuring ; instruments are also included. (auth)
C. H. Hogg; L. D. Weber; M. W. Echo
Heater treater waste heat recovery system
A waste heat recovery system for a heater treater which elevates the overall energy imparted into crude oil from a finite amount of combustion gases is described. The system includes a vertical heat exchanger supported from the shell of the heater treater. The exchanger has an outer housing within which a plurality of longitudinally arranged tubes are disposed. Untreated crude
Rapid vertical tectonics in ductile continental crust
Research over the past two decades has shown that in regions of moderately high heat flow, the lower continental crust is ductile enough to flow on geological timescales. Vertical motions taking place within continental interiors produce localized features such as intracratonic basins and domes, and the results of this thesis indicate that ductile crustal flow can contribute significantly to the formation of these otherwise enigmatic features. A major goal of this thesis has been to analyze, quantitatively, the behaviour of loaded continental crust where a ductile layer is present. Specifically, I examine the long-term effects of sublithospheric heating events on crust with embedded density loads. Density anomalies within the crust can be initially supported by elastic stresses but sag appreciably if the elastic crust is thinned modestly. Beginning with a semi-analytic approach, I estimate the additional subsidence that would result from thermal reactivation, and introduce the previously unmodelled phenomenon of thermal annealing of stresses at the base of the elastic crust. In basins caused by intracrustal density loads, reactivated subsidence can be significant (of the order of 1 km, enough to account for about one quarter of the total Michigan basin subsidence). If the crust is sufficiently weakened, the long-term result is detachment of the load followed by rebound and inversion of the basin to form a dome. To model this phenomenon I use a full thermal and viscoelastic finite-element model, and find that such load detachment can occur for geologically reasonable load densities in high heat flow regions. Strikingly, the total upward displacement of material from depth during rebound can be as much as 10 km, enough to exhume the basin completely and expose basement rocks to some depth. Exhumation is rapid, lasting only about 5 to 10 million years. This raises the interesting question of what field evidence might support such a history for a dome: the results of my simulations are consistent with many of the features of metamorphic core complexes in the southern Basin and Range province, although an additional mechanism may be required to explain the exposure of rocks that originated at mid-crustal depths.
Pearse, Jillian
FFTF vertical sodium storage tank preliminary thermal analysis
In the FFTF Shutdown Program, sodium from the primary and secondary heat transport loops, Interim Decay Storage (IDS), and Fuel Storage Facility (FSF) will be transferred to four large storage tanks for temporary storage. Three of the storage tanks will be cylindrical vertical tanks having a diameter of 28 feet, height of 22 feet and fabricated from carbon steel. The fourth tank is a horizontal cylindrical tank but is not the subject of this report. The storage tanks will be located near the FFTF in the 400 Area and rest on a steel-lined concrete slab in an enclosed building. The purpose of this work is to document the thermal analyses that were performed to ensure that the vertical FFTF sodium storage tank design is feasible from a thermal standpoint. The key criterion for this analysis is the time to heat up the storage tank containing frozen sodium at ambient temperature to 400 F. Normal operating conditions include an ambient temperature range of 32 F to 120 F. A key parameter in the evaluation of the sodium storage tank is the type of insulation. The baseline case assumed six inches of calcium silicate insulation. An alternate case assumed refractory fiber (Cerablanket) insulation also with a thickness of six inches. Both cases assumed a total electrical trace heat load of 60 kW, with 24 kW evenly distributed on the bottom head and 36 kW evenly distributed on the tank side wall.
Irwin, J.J.
Distance cues for vertical vergence adaptation.
Vertical vergence can be trained to respond to vertical and/or horizontal conjugate eye position, horizontal vergence, and vertical head tilt. This cross-coupling is manifest as a vertical phoria aftereffect (monocular vertical vergence response) that varies with direction and distance of gaze. The function of the spatially dependent adaptation is to maintain the calibration between vertical eye alignment and intended placement of the two retinal images. Oculomotor adaptation stabilizes our sense of spatial localization and calibrates a body-referenced coordinate representation of visual space that is necessary for visually guided motor responses. We have tested the possible association of vertical phoria adaptation with perceptual cues to distance in the absence of any other associated motor activity. During adaptive training, vertical disparity vergence was associated with variations of perceptual distance cues (including loom, overlap, relative size, and relative motion), oculomotor distance cues (horizontal vergence), or a combination of both classes of cues. We observed that in a 2-h period the open-loop (monocular) vertical vergence response could not be trained to occur as an aftereffect in association with the perceptual cues to distance, whereas it could be trained in association with oculomotor cues. We conclude that the spatial specificity of vertical vergence aftereffects caused by short-term adaptation results from an associated cross-coupling with supranuclear sources of oculomotor activity. PMID:8539011
Schor, C M; McCandless, J W
Heat Without Heat
Logic of the Second Law of Thermodynamics demands acquisition of naked entropy. Accordingly, the leanest liaison between systems is not a diathermic membrane, it is a purely informational tickler, leaking no appreciable energy. The subsystem here is a thermodynamic universe, which gets `heated' entropically, yet without gaining calories. Quantum Mechanics graciously supports that(Lubkin, E. and Lubkin, T., International Journal of Theoretical Physics,32), 933-943 (1993) (at a cost of about 1 bit) through entanglement---across this least permeable of membranes---with what is beyond that universe. Heat without heat(Also v. forthcoming Proceedings of the 4th Drexel University Conference of September 1994) is the aspirin for Boltzmann's headache, conserving entropy in mechanical isolation, even while increasing entropy in thermodynamic isolation.
Lubkin, Elihu
On the Vertical Structuring of Gigantic Jets
Gigantic Jets (GJs) are large-scale electrical discharges between the thundercloud tops and the lower ionosphere. It is estimated that an individual GJ can contribute as much as cloud-to-ground lightning in discharging a thunderstorm system, transferring hundreds of coulombs from thundercloud to the ionosphere [Cummer et al., Nat. Geosci., 2, 617-620, 2009]. GJs are initiated deep inside the thundercloud as intracloud lightning discharges. Owing to a charge imbalance, meaning the upper charge center is depleted with respect to the midlevel charge center, the upward-directed lightning leaders manage to escape through the thundercloud top to form GJs [Krehbiel et al., Nat. Geosci., 1, 233-237, 2008]. As a GJ leader crosses the stratosphere its streamer zone becomes longer and longer, due to the dynamics of streamer growth in a medium with exponentially-decreasing air density, such as in the Earth's atmosphere [Raizer et al., GRL, 33, L23801, 2006]. The speed at which a leader propagates is limited by the air heating of every newly formed leader section, rate of which is slower at upper altitudes in the Earth's atmosphere [da Silva and Pasko, GRL, 39, L13805, 2012]. Despite the expected deceleration of an upward-directed leader, GJs are observed to accelerate as they approach the ionosphere. To address this issue, we propose a simple time-dynamic model for GJ propagation that simulates the upward propagation of a leader discharge accounting for the effects of the expansion of its streamer zone. We propose that the GJ acceleration is a consequence of its vertical structuring and, therefore, can be used to trace the transition altitude between the leader and streamer zone sections of GJs [da Silva and Pasko, GRL, 40, 12, 3315-3319, 2013]. Leaders and streamers are very different electrical discharges in terms of the degree of ionization, temperature, and composition of the plasma inside their channels. A correct description of the vertical structuring of GJs is of fundamental importance for evaluation of their effects in the stratosphere and mesosphere.
Da Silva, C.; Pasko, V. P.
Importance of capturing heliospheric variability for studies of thermospheric vertical winds
Using the Global Ionosphere Thermosphere Model with observed real-time heliospheric input data, the magnitude and variability of thermospheric neutral vertical winds are investigated. In order to determine the role of variability in the Interplanetary Magnetic Field (IMF) and solar wind density on the neutral wind variability, the heliospheric input data are smoothed. The effects of smoothing the IMF and solar wind and density on the vertical winds are simulated for the cases of no smoothing, 5-minute, and 12-minute smoothing. Various vertical wind acceleration terms, such as the nonhydrostatic acceleration, are quantified. Polar stereographic projections of the variabilities of vertical wind and ion flows are compared to highlight existing correlations. Overall, the smoother, that is, the less variable the IMF and solar wind parameters are, the weaker are the magnitude and the variability of the thermospheric vertical winds. Weaker IMF variability leads to smaller variability in ion flows, which in turn negatively impacts the variability and the magnitude of Joule heating. Small-scale temporal variation of the vertical wind acceleration, and thus the variability of the vertical wind, is dominated by the nonhydrostatic term that is controlled primarily by the temporal variation of the Joule heating, which in turn is related to ion flow variations that are shaped by the IMF in the high-latitude thermosphere. Wavelet analysis of the vertical wind data shows that gravity waves of �5 and �10-minute periods are more prominent when the model is run with high-resolution real-time IMF and solar wind data. Better capturing of the temporal variation of the IMF and solar wind parameters is crucial for modeling the variability and magnitude of thermospheric vertical winds.
Yi?it, Erdal; Ridley, Aaron J.; Moldwin, Mark B.
Vertical Sizing of Cirrus Clouds using the 1.38 ?m Spectral Lines and MODIS Data
Atmospheric albedo and heating rates in cloudy conditions are dependent on the vertical inhomogeneity of clouds. For example, small ice crystal sizes aloft coupled with larger sizes at the cloud base would reflect more solar radiation as compared to the use of an averaged ice crystal size for the same cloud. Significant variability of the heating rate also occurs in association with vertical inhomogeneity. In situ measurements from the airborne optical probe, replicator, and cloud scope clearly illustrate the vertical distribution of ice crystal size and shape. We have developed an approach to infer the vertical profile of mean effective particle size on the basis of the spectral line reflectance of the 1.38 ?m water vapor band. In it, seventeen narrow bands of various water vapor absorption strengths have been selected. The physical principle for this approach is based on the fact that the reflectance in strong absorptive wavelengths is most sensitive to cloud top properties, whereas the reflectance in less absorptive wavelengths senses the microphysical properties deeper into the cloud. To test this concept, we have prescribed several cloud vertical structures and used an adding-doubling radiative transfer program coupled with the correlated k-distribution method to calculate the look-up tables of reflectance for a variety of cloud settings. We show some success of hypothetical retrieval exercises by applying a ?2 minimization principle. The vertical sizing idea described above has been applied to the MODIS visible and three near-IR channels and we demonstrate that it is possible to derive two vertical ice crystal sizes from a combination of these channels. For validation purposes, we have selected a number of cirrus scenes over the ARM Southern Great Plain site and compared the retrieved vertical ice crystal sizes with the ground-based cloud radar retrieval values. The vertical sizing results determined from the 1.38 ?m spectral lines and MODIS data will be presented.
Wang, X.; Liou, K.; Ou, S.
[Occlusal vertical dimension in removable complete dentures].
In removable complete dentures, the occlusal vertical dimension is an important factor for patients' satisfaction with aesthetics. An excessively reduced occlusal vertical dimension is especially likely to lead to complaints about aesthetics, whereas an increased occlusal vertical dimension may lead to discomfort and a decision not to wear the complete dentures. There are various methods for determining the occlusal vertical dimension in complete dentures, based on the vertical dimension in the rest position of the mandible or on phonetics. However, none of the methods have proven to be clearly superior, in terms of reliability, than the others. The assessment of the occlusal vertical dimension will become more reliable if several methods are used simultaneously. Moreover, knowledge of the characteristics of the ageing face is essential. PMID:22292357
den Haan, R; Witter, D J
Simplified numerical study of evaporation processes inside vertical tubes
The paper presents a simplified numerical model of evaporation processes inside vertical tubes. In this model only the temperature fields in the fluid domain (the liquid or two-phase mixture) and solid domain (a tube wall) are determined. Therefore its performance and efficiency is high. The analytical formulas, which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length, are used in this model. The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.
Oc?o?, Pawe?; Nowak, Marzena; ?opata, Stanis?aw
Vertical tunnel field-effect transistor
The realization of a novel vertically grown tunnel field-effect transistor (FET) with several interesting properties is presented. The operation of the device is shown by means of both experimental results as well as two-dimensional computer simulations. This device consists of a MBE-grown, vertical p-i-n structure. A vertical gate controls the band-to-band tunneling width, and hence the tunneling current. Both n-channel
K. K. Bhuwalka; S. Sedlmaier; A. K. Ludsteck; C. Tolksdorf; J. Schulze; I. Eisele
Salt domes, pit craters, and dry steam fields - Heat pipe applications
Heat pipes operating vertically with the heat source at the lower end have, in theory, high efficiencies over pipe lengths exceeding 100 meters. Three geological applications are possible: (1) heat pipe-nuclear reactor couples in salt domes, (2) heat pipes penetrating the crust of lava lakes, and (3) heat pipes tapping high enthalpy steam fields. Environmental aspects of these pollution-free energy
J. Green
Heat Pipes
Describes the construction, function, and applications of heat pipes. Suggests using the heat pipe to teach principles related to heat transfer and gives sources for obtaining instructional kits for this purpose. (GS)
Lewis, J.
Solar and ground source heat-pump system
Theoretical and experimental studies were performed for a solar-ground source heat-pump (SGSHP) system with a vertical double-spiral coil (VDSC) ground heat-exchanger (GHX). The heating mode of the SGSHP system is alternated between a solar energy-source heat-pump (SSHP) and a ground-source heat-pump (GSHP) using a low-grade energy utilization system built by the authors. The measured performances were for the SSHP, GSHP
Yuehong Bi; Tingwei Guo; Liang Zhang; Lingen Chen
Non-Darcy regime mixed convection on vertical plates in saturated porous media with lateral mass flux
Summary A unified treatment is presented of mixed convection on vertical plates embedded in fluid saturated porous media with prescribed variable plate temperature or surface heat flux for the case of non-Darcy limiting regime. The plates are permeable with lateral mass flux. By suitable similarity transformations, it is shown that the two problems of prescribed temperature and prescribed heat flux
G. Ramanaiah; G. Malarvizhi
Finite-difference analysis of the MDH Stokes problem for a vertical plate with Hall and ion-slip currents
An explicit finite-difference method is employed to study the MHD free convection heat generating fluid past an impulsively started vertical infinite plate when a strong magnetic field is applied perpendicular to the plate. The velocity and temperature profiles are shown on graphs and the results are discussed in terms of Hall parameter, ionslip parameter, heat source parameter, and the Gr
P. C. Ram
Spectral characteristics of two-dimensional turbulent convection in a vertical slot
ive flow follows the law E(k) k-n\\/s while the temperature fluctuation energy follows ET(k ) k -7\\/5. The possibility of realizing turbulent flow with such spectral dependences in a vertical slot with heat insulated boundaries is shown there. The energy distribution over the spectrum depends substantially on the heat elimination conditions on the slot side walls. Flow in a slot
V. A. Barannikov; P. G. Frik; V. G. Shaidurov
Flow boiling of a highly viscous pseudoplastic fluid in vertical tubes
An experimental study of flow boiling heat transfer to a highly viscous fluid in vertical downward flow is presented for a consistency index ?0 = 0.71�26.66 Pa sn, tube diameters D = 5.34, 7.71 and 10.27 mm, mass velocity G = 4.36�53.4 kg m?2s?1, a quality X = 0.0�0.54 and a heat flux q = 1.43�14.35 kW m?2. A correction
Liu Junhong; Ye Lin; Liu Hesheng; Cui Bo
OTEC performance tests of the Carnegie-Melon University vertical fluted-tube condenser
Performance tests results on a vertical fluted-tube condenser are reported. The condenser was free of operational problems and performed in a stable and repeatable manner. At nominal design conditions (a heat duty of 3.2 million Btu\\/hr and a water flow rate of 3200 gpm), the overall heat transfer coefficient (U sub zero) was 1040 Btu\\/hr sq ft F and the
L. G. Lewis; N. F. Sather
Carbothermic reduction with parallel heat sources
Disclosed are apparatus and method of carbothermic direct reduction for producing an aluminum alloy from a raw material mix including aluminum oxide, silicon oxide, and carbon wherein parallel heat sources are provided by a combustion heat source and by an electrical heat source at essentially the same position in the reactor, e.g., such as at the same horizontal level in the path of a gravity-fed moving bed in a vertical reactor. The present invention includes providing at least 79% of the heat energy required in the process by the electrical heat source.
Troup, Robert L. (Murrysville, PA); Stevenson, David T. (Washington Township, Washington County, PA)
Turbulent natural convection in vertical parallel-plate channels
The problem of buoyancy driven turbulent flow in parallel-plate channels is investigated. The investigation is limited to vertical channels of uniform cross-section with different modes of heating. The details of the flow and thermal fields are obtained from the solution of the conservation equations of mass, momentum, and energy in addition to equations of the low Reynolds number turbulence model. The study covers Rayleigh number ranging from 105 to 107 and focuses on the effect of channel geometry on the characteristic of the flow and thermal fields as well as the local and average Nusselt number variation. A Nusselt number correlation has been developed in terms of a modified Rayleigh number and channel aspect ratio for the cases of symmetrically heated isothermal and isoflux conditions.
Badr, H. M.; Habib, M. A.; Anwar, S.; Ben-Mansour, R.; Said, S. A. M.
Monitoring soil water content by vertical temperature variations.
The availability of high sensitivity temperature sensors (0.001 K sensitivity platinum resistors), which can be positioned at intervals of a few centimeters along a vertical profile in the unsaturated zone, allows short-term in situ determinations-one day or even less-of the thermal diffusivity. The development of high data storage capabilities also makes this possible over long periods and the relative variations in thermal diffusivity allow the monitoring of the variations in water content. The processing of temperature measurements recorded at different depths is achieved by solving the heat equation, using the finite elements method, with both conductive and convective heat transfers. A first set of measurements has allowed this approach to be validated. Water content variations derived from thermal diffusivity values are in excellent agreement with TDR measurements carried out on the experimental site at Boissy-le-Ch�tel (Seine et Marne, France). PMID:23834312
Bechkit, Mohamed Amine; Flageul, S�bastien; Guerin, Roger; Tabbagh, Alain
On heat flow singularities over mid-ocean ridges
Current interpretations of heat flow values within the framework of plate tectonics concepts fail to reproduce the available observations for the oceanic ridge crests and give heat flow singularities. A new mathematically tractable theory of vertical intrusion (using a nonuniform temperature distribution at the ridge crest) has been constructed that shows a reasonable fit between predicted and observed heat flows.
E. A. Lubimova; V. N. Nikitina
Measurement of the heat transfer coefficient for walls
A test set-up was developed for the determination of the external heat transfer coefficient of walls under actual outdoor conditions. The set-up was used to measure the convective heat transfer coefficient for the central region of a vertical wall. Outdoor tests were carried out under a wide range of conditions and the heat transfer coefficient was correlated with wind speed.
S. E. G. Jayamaha; N. E. Wijeysundera; S. K. Chou
Performance of a compact, spiral coil heat exchanger
A spiral coil heat exchanger consists of a number of horizontal layers of spirally wound, finned tubes connected to vertical manifolds at the inner and outermost turns of each coil. This design has advantages in heat recovery and air-conditioning applications. Two theoretical models to predict the performance of this compact heat exchanger are presented based upon unmixed and mixed air-flow
J. C. Ho; N. E. Wijeysundera; S. Rajasekar; T. T. Chandratilleke
Direct contact heat exchangers in geothermal power production
The direct contact cycle can be advantageously utilized in the production of power from liquid dominated geothermal resources. The heat from the geothermal resource is transferred to a selected working fluid by direct countercurrent contact in a vertical perforated trayed tower. The direct contactor is divided into three heat transfer zones where heat is extracted from the hot water by
I. Sheinbaum
Crystal Ice Formation of Solution and Its Removal Phenomena on a Vertical Cooled Plate
Experimental and analytical studies for freezing phenomena of ethylene glycol solution on a vertical cooled polyvinyl-chloride plate have been performed. It is found that the crystal ice formed on the vertical plate is removed from the plate surface due to buoyancy force acting on the crystal ice. It is shown that the crystal ice formed on the vertical plate slides along the plate surface due to buoyancy force and the crystal ice grows in a shape of sheet by joining with the neighbour ice. The number of the removed ice per unit of time is, therefore, decreased as compared to that for the horizontal plate. It is found that the onset of ice removal condition is related to the heat fluxes from the plate surface to the plate and from the plate surface to the solution. The ice removal occurs easily for a vertical plate than for a horizontal one.
Hirata, Tetsuo; Ishikawa, Masaaki; Matsuzaki, You
It has been widely argued recently that agriculture is undergoing a process of vertical integration with allied industries. One of the worldwide ways of vertical integration in agriculture is contract farming. Contract farming is a continually evolving process. Worldwide applications of contract farming have shown that the terms of contracts are shaped by their own conditions and varied from product
Erkan Rehber
Marsh vertical accretion via vegetative growth
Coastal marshes accrete vertically in response to sea-level rise and subsidence. Inadequate accretion and subsequent conversion of coastal marshes to open water generally is attributed to inadequate mineral sedimentation because mineral sedimentation is widely assumed to control accretion. Using 137Cs dating to determine vertical accretion, mineral sedimentation, and organic matter accumulation, we found that accretion varied with organic accumulation rather
John A. Nyman; Russel J. Walters; Ronald D. Delaune; William H. Patrick
Control system for a vertical axis windmill
A vertical axis windmill having a rotating structure is provided with a series of articulated vertical blades whose positions are controlled to maintain a constant RPM for the rotating structure, when wind speed is sufficient. A microprocessor controller is used to process information on wind speed, wind direction and RPM of the rotating structure to develop an electrical signal for
Silicon Micromachined Vertical Structures for Nanoparticle Separation
In this thesis we described a new approach to design, fabricate, package and test three silicon based porous vertical structures for nanoparticle separations. These vertical structures stand in between two microfluidic channels. In these walls nano channels that connect the two adjacent microchannels are embedded. Fluid and small particles can penetrate the walls through the embedded nano channels while particles
C. Shen
Comparison of Horizontal and Vertical Probe Coils.
The report presents a comparison of horizontal and vertical probe coils of eddy current testing when placed above a homogeneous conducting half space. The trend of the impedance curves for both horizontal and vertical coils against lift-off variation is t...
M. M. Ashraf
Exergoeconomic analysis of a solar assisted ground-source heat pump greenhouse heating system
EXCEM analysis may prove useful to investigators in engineering and other disciplines due to the methodology are being based on the quantities exergy, cost, energy and mass. The main objective of the present study is to investigate between capital costs and thermodynamic losses for devices in solar assisted ground-source heat pump greenhouse heating system (SAGSHPGHS) with a 50 m vertical
Critical heat flux experiments and correlation in a long, sodium-heated tube
Critical heat flux (CHF) experiments were performed in the Steam Generator Test Facility (SGTF) at Argonne National Laboratory for application to liquid metal fast breeder reactor steam generators. The test section consisted of a single, straight, vertical, fullscale LMFBR steam generator tube with force-circulated water boiling upwards inside the tube heated by sodium flowing countercurrent in a surrounding annulus. The
D. M. France; R. D. Carlson; T. Chiang; W. J. Minkowycz
Calculations of the anomalies of the vertical temperature gradient using the horizontal temperature distribution
This paper examines the determination of heat flow at the earth surface in relation to geothermal studies. Anomalies of the vertical temperature gradient can be calculated with the Hilbert transformation of surface temperature measured along a profile. The procedure is carried out with temperature values over the Supetau anticline at the Fergana basin.
R. Roesler; H. Lindner; C. Oelsner
Experimental investigation on drift-flux parameters for subcooled boiling in a vertical annulus
Drift-flux parameters were determined by direct measurements of distributions of local void fraction, vapor velocity and liquid velocity for the subcooled boiling of water in a vertical annulus with a heated inner tube at its center. Using the measured profiles, the drift-flux parameters were calculated based on the definitons, and then compared with those predicted by the existing correlations. The
G. C. Park
Oak Ridge National Laboratory Vertical Tube Evaporator Pilot Plant Annual Report for Fiscal Year 1969.
The report summarizes the down-flow heat transfer performance of enhanced surface tubes and operations at the four-effect Vertical Tube Evaporator Pilot Plant at the Office of Saline Water East Coast Test Station, Wrightsville Beach, North Carolina. Avera...
C. Wong E. N. Sieder J. T. Callahan
Neptune Clouds Showing Vertical Relief
This Voyager 2 high resolution color image, taken 2 hours before closest approach, provides obvious evidence of vertical relief in Neptune's bright cloud streaks. These clouds were observed at a latitude of 29 degrees north near Neptune's east terminator. The linear cloud forms are stretched approximately along lines of constant latitude and the sun is toward the lower left. The bright sides of the clouds which face the sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the sun. These shadows are less distinct at short wavelengths (violet filter) and more distinct at long wavelengths (orange filter). This can be understood if the underlying cloud deck on which the shadow is cast is at a relatively great depth, in which case scattering by molecules in the overlying atmosphere will diffuse light into the shadow. Because molecules scatter blue light much more efficiently than red light, the shadows will be darkest at the longest (reddest) wavelengths, and will appear blue under white light illumination. The resolution of this image is 11 kilometers (6.8 miles per pixel) and the range is only 157,000 kilometers (98,000 miles). The width of the cloud streaks range from 50 to 200 kilometers (31 to 124 miles), and their shadow widths range from 30 to 50 kilometers (18 to 31 miles). Cloud heights appear to be of the order of 50 kilometers (31 miles). This corresponds to 2 scale heights. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.
Heat waves
The concept of transmission of heat by waves is reviewed and interpreted. The notion of an effective thermal conductivity, an effective heat capacity, and relaxation functions for heat and energy is introduced along lines used recently to describe the elastic response of viscous liquids. An annotated bibliography of the literature on heat waves, from the beginning until now, gives a
D. D. Joseph; Luigi Preziosi
Heat pumps
What electric heating system is the most efficient in moderate climates? This reading, part of a series about the future of energy, introduces students to the modern heat pump. Students read about the efficiency of heat pumps and the three types currently being used in homes. A simple explanation of how a heat pump works is offered. Copyright 2005 Eisenhower National Clearinghouse
Project, Iowa P.
Entirely passive heat pipe apparatus capable of operating against gravity
The disclosure is directed to an entirely passive heat pipe apparatus capable of operating against gravity for vertical distances in the order of 3 to 7 meters and more. A return conduit into which an inert gas is introduced is used to lower the specific density of the working fluid so that it may be returned a greater vertical distance from condenser to evaporator.
Koenig, Daniel R. (Santa Fe, NM)
Composite resonator vertical cavity laser diode
The use of two coupled laser cavities has been employed in edge emitting semiconductor lasers for mode suppression and frequency stabilization. The incorporation of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. Composite resonators can be utilized to control spectral and temporal properties within the laser; previous studies of coupled cavity vertical cavity lasers have employed photopumped structures. The authors report the first composite resonator vertical cavity laser diode consisting of two optical cavities and three monolithic distributed Bragg reflectors. Cavity coupling effects and two techniques for external modulation of the laser are described.
Choquette, K.D.; Hou, H.Q.; Chow, W.W.; Geib, K.M.; Hammons, B.E.
Heating Structures Derived from Satellite
Rainfall is a key link in the hydrologic cycle and is a primary heat source for the atmosphere. The vertical distribution of latent-heat release, which is accompanied by rainfall, modulates the large-scale circulations of the tropics and in turn can impact midlatitude weather. This latent heat release is a consequence of phase changes between vapor, liquid, and solid water. The Tropical Rainfall Measuring Mission (TRMM), a joint U.S./Japan space project, was launched in November 1997. It provides an accurate measurement of rainfall over the global tropics which can be used to estimate the four-dimensional structure of latent heating over the global tropics. The distributions of rainfall and inferred heating can be used to advance our understanding of the global energy and water cycle. This paper describes several different algorithms for estimating latent heating using TRMM observations. The strengths and weaknesses of each algorithm as well as the heating products are also discussed. The validation of heating products will be exhibited. Finally, the application of this heating information to global circulation and climate models is presented.
Tao, W.-K.; Adler, R.; Haddad, Z.; Hou, A.; Kakar, R.; Krishnamurti, T. N.; Kummerow, C.; Lang, S.; Meneghini, R.; Olson, W.
Heat transfer from square pin-fin heat sinks using air impingement cooling
Experimental and numerical results are presented for heat transfer from a C4 mounted organic land grid array (OLGA) thermal test chip cooled by air impingement. Five heat sink geometries were investigated for Reynolds numbers ranging from 9,000 to 26,000. The dimensionless nozzle-to-heat sink vertical spacing z\\/D was varied between 2 and 12. In this study, we investigate the interactions between
Jim G. Maveety; Henry H. Jung
Water Flux Estimation by Multi Functional Heat Pulse Probe for Variably Saturated Sandy Soil
A small multi-functional heat pulse probe (MFHPP) with 5 stainless tube that includes a heater, two vertically and two horizontally installed thermistors was developed for water flux density measurement. A heat pulse generated from heater tube was measured at thermistor tubes 6mm away from the heater. Vertically installed thermistor measurement was affected by water flow and the flux was estimated
Y. Mori; A. P. Mortensen; J. W. Hopmans; G. J. Kluitenberg; M. Inoue
Effect of void fraction models on the film thickness of R134a during downward condensation in a vertical smooth tube
In the present study, the void fraction and film thickness of pure R-134a flowing downwards in a vertical condenser tube are indirectly determined using relevant measured data together with an annular flow model and various void fraction models reported in the open literature. The vertical test section is a countercurrent flow double tube heat exchanger with refrigerant flowing down in
The prediction of long term monthly mean daily solar gains through vertical single and double clear glazing at sites distributed throughout the UK
A simple approximate method has been developed for estimating long term monthly mean daily solar heat gains per unit area for vertical windows for sites within the UK. The method enables the monthly mean solar gains through vertical single and double glazing of any orientation to be estimated for each of the Department of Energy degree day regions, using a
G. G. Rodgers; J. K. Page; I. D. Colquhoun; J. L. Thompson
Natural Convection in a Vertical Rectangular Cavity Filled with a Non-Newtonian Power Law Fluid and Subjected to a Horizontal Temperature Gradient
A study of natural convection, in a vertical rectangular cavity filled with a non-Newtonian fluid and subjected to uniform heat flux along the vertical side walls, is carried out numerically by solving the full governing equations. In the limit of a tall enclosure, these equations are considerably reduced by using the parallel flow approximation. Solutions for the flow and temperature
M. Lamsaadi; M. Na�mi; M. Hasnaoui; M. Mamou
Crystal Ice Formation of Solution and Its Removal Phenomena around Vertical Cooled Cylinder
Experimental and analytical studies for freezing phenomena of ethylene glycol solution around a vertical cooled polyvinyl-chloride cylinder have been performed. It is found that the crystal ice formed around the vertical cylinder is removed from the cylinder surface due to buoyancy force acting on the crystal ice. The crystal ice slides along the cylinder surface due to buoyancy force and grows in a shape of tube by joining with the neighbour ice. It is shown that the onset of ice removal condition is related to the heat flux at the cylinder surface when the latent heat of fusion is discharged with freezing, and that the heat flux ratio of 'from the cylinder surface into the cylinder' to 'from the cylinder surface to the solution' is an important parameter for the onset conditions. The ice removal occurs easily for short cylinders than for long ones.
Hirata, Tetsuo; Ishikawa, Masaaki; Akutsu, Nobuaki
Vertical Motions of Oceanic Volcanoes
Oceanic volcanoes offer abundant evidence of changes in their elevations through time. Their large-scale motions begin with a period of rapid subsidence lasting hundreds of thousands of years caused by isostatic compensation of the added mass of the volcano on the ocean lithosphere. The response is within thousands of years and lasts as long as the active volcano keeps adding mass on the ocean floor. Downward flexure caused by volcanic loading creates troughs around the growing volcanoes that eventually fill with sediment. Seismic surveys show that the overall depression of the old ocean floor beneath Hawaiian volcanoes such as Mauna Loa is about 10 km. This gross subsidence means that the drowned shorelines only record a small part of the total subsidence the islands experienced. In Hawaii, this history is recorded by long-term tide-gauge data, the depth in drill holes of subaerial lava flows and soil horizons, former shorelines presently located below sea level. Offshore Hawaii, a series of at least 7 drowned reefs and terraces record subsidence of about 1325 m during the last half million years. Older sequences of drowned reefs and terraces define the early rapid phase of subsidence of Maui, Molokai, Lanai, Oahu, Kauai, and Niihau. Volcanic islands, such as Maui, tip down toward the next younger volcano as it begins rapid growth and subsidence. Such tipping results in drowned reefs on Haleakala as deep as 2400 m where they are tipped towards Hawaii. Flat-topped volcanoes on submarine rift zones also record this tipping towards the next younger volcano. This early rapid subsidence phase is followed by a period of slow subsidence lasting for millions of years caused by thermal contraction of the aging ocean lithosphere beneath the volcano. The well-known evolution along the Hawaiian chain from high to low volcanic island, to coral island, and to guyot is due to this process. This history of rapid and then slow subsidence is interrupted by a period of minor uplift lasting a few hundred thousand years as the island migrates over a broad flexural arch related to isostatic compensation of a nearby active volcano. The arch is located about 190�30 km away from the center of volcanic activity and is also related to the rejuvenated volcanic stage on the islands. Reefs on Oahu that are uplifted several tens of m above sea level are the primary evidence for uplift as the islands over-ride the flexural arch. At the other end of the movement spectrum, both in terms of magnitude and length of response, are the rapid uplift and subsidence that occurs as magma is accumulated within or erupted from active submarine volcanoes. These changes are measured in days to years and are of cm to m variation; they are measured using leveling surveys, tiltmeters, EDM and GPS above sea level and pressure gauges and tiltmeters below sea level. Other acoustic techniques to measure such vertical movement are under development. Elsewhere, evidence for subsidence of volcanoes is also widespread, ranging from shallow water carbonates on drowned Cretaceous guyots, to mapped shoreline features, to the presence of subaerially-erupted (degassed) lavas on now submerged volcanoes. Evidence for uplift is more limited, but includes makatea islands with uplifted coral reefs surrounding low volcanic islands. These are formed due to flexural uplift associated with isostatic loading of nearby islands or seamounts. In sum, oceanic volcanoes display a long history of subsidence, rapid at first and then slow, sometimes punctuated by brief periods of uplift due to lithospheric loading by subsequently formed nearby volcanoes.
Clague, D. A.; Moore, J. G.
Vertical stratification in arthropod spatial distribution research.
Spatial heterogeneity within individual host trees is often overlooked in surveys of phytophagous arthropod abundance and distribution. The armored scale Aulacaspis yasumatsui is controlled by the predator Rhyzobius lophanthae to a greater degree on leaves at 75-cm height than on leaves at ground level within its host tree Cycas micronesica. The direct influence of elevation on the predator indirectly generates vertical heterogeneity of the scale insect. Arthropod sampling schemes that fail to include all strata within the vertical profile of the host tree species may generate misleading outcomes. Results indicate that sub-meter increments can reveal significant differences in vertical distribution of phytophagous insects, and that inclusion of observations on other organisms that interact with the target arthropod may illuminate determinants of vertical heterogeneity. PMID:24567772
Marler, Thomas E
Laparoscopic Cholecystectomy after Vertical Banded Gastroplasty.
Following vertical gastroplasty, laparoscopic cholecystectomy has been performed in 27 consecutive patients who developed symptomatic gallstones. Dissection identified structures without difficulty in these patients, and problems were not encountered in these procedures with the laparoscopic technique PMID:10742757
Deitel; Smith; Harmantas
Confocal profilometer with nanometric vertical resolution.
An optical system is described which is based on the method of Kobayashi et al. The instrument is capable of simultaneous confocal imaging and profilometry with nanometric (nm) vertical resolution. The profile is independent of the reflectivity of the sam...
D. J. Butler A. Horsfall M. Hrynevych P. D. Kearney K. A. Nugent
Vertical Breakout Behavior of the Hydrostatic Anchor.
The vertical breakout behavior of the hydrostatic anchor depends greatly upon the anchor geometry including anchor diameter and skirt length, the soil strength properties, and the pressure difference between the ambient pressure and that underneath the po...
M. C. Wang V. A. Nacci K. R. Demars
High Performance Vertical Organic Field Effect Transistors.
This is a productive research project (12 papers in three years) aiming to understand the potential of conjugated polymer in a wide range of organic electronic devices - vertical transistors,solar cells and photodetectors, memory devices, as well as graph...
Y. Yang
Vertical Axis Wind Turbine Foundation parameter study
The dynamic failure criterion governing the dimensions of prototype Vertical Axis Wind Turbine Foundations is treated as a variable parameter. The resulting change in foundation dimensions and costs is examined.
Lodde, P.F.
Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey
30. BEARING SHOE / VERTICAL / DIAGONAL / UPPER AND LOWER CHORD DETAIL OF DECK TRUSS. VIEW TO NORTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE
23. INCLINED END POST / VERTICAL / DIAGONAL / PORTAL BRACING DETAIL. VIEW TO SOUTHEAST. - Abraham Lincoln Memorial Bridge, Spanning Missouri River on Highway 30 between Nebraska & Iowa, Blair, Washington County, NE
Evaluation of a Vertical Conveyorized Electric Grill.
A continuous vertical electric grill was evaluated from an engineering, food production and food acceptance point of view. Production rate, consistent with the quality criteria established, was found to be 250 hamburger patties per hour. The unit was limi...
R. L. Bernazzani G. Bell
Vertical Datum Conversions for Regional Coastal Management.
Transforming surveyed elevations and water depths to desired vertical datums is an essential step in building a regional coastal management plan. Regional coastal management plans are based on sediment volume changes and numerical simulations of regional ...
J. M. Wozencraft
Vertically-Shaped Tunable MEMS Resonators
We report the development of tunable comb-resonators that use vertically-shaped comb-fingers as electrostatic springs. By restricting our design modifications to the vertical dimension, the tunability is achieved without increasing the device footprint. Three-dimensional finite element analysis was used to evaluate the effects of geometry and design on electrostatic spring strength and linearity. All structural components were fabricated using gray-scale technology,
Brian Morgan; Reza Ghodssi
On vertical profile of ozone at Syowa
The difference in the vertical ozone profile at Syowa between 1966-1981 and 1982-1988 is shown. The month-height cross section of the slope of the linear regressions between ozone partial pressure and 100-mb temperature is also shown. The vertically integrated values of the slopes are in close agreement with the slopes calculated by linear regression of Dobson total ozone on 100-mb temperature in the period of 1982-1988.
Chubachi, Shigeru
Strategic choice along the vertical coordination continuum
Starting from the generalized notion of a vertical coordination continuum introduced by Williamson and others, the article more specifically defines the nature of the continuum, especially the array of hybrid strategies. The continuum as presented includes five distinct groups of strategy�spot markets, specification contracts, relation-based alliances, equity-based alliances, and vertical integration. The article then presents a decision making framework that
H. Christopher Peterson; Allen F. Wysocki; Stephen B. Harsh
Long vertical shaft bioreactor of simplified design
An improved long vertical shaft bioreactor for the treatment of degradable waste is provided wherein the head tank or basin surmounting the vertical downcomer and riser chambers is surrounded by a foam oxidation vessel. Conduits are provided between the head tank and the foam vessel through which (A) foam accumulated in the head tank is passed to the foam vessel and (B) through which excess fluid in the head tank may be vented.
Pollock, D.C.
Effect of vertical motion on current meters
The effect of vertical motion on the performance of current meters at various stream velocities was evaluated to determine whether accurate discharge measurements can be made from a bobbing boat. Three types of current meters--Ott, Price, and vane types--were tested under conditions simulating a bobbing boat. A known frequency and amplitude of vertical motion were imparted to the current meter, and the related effect on the measured stream velocity was determined. One test of the Price meter was made under actual conditions, using a boat and standard measuring gear. The results of the test under actual conditions verified those obtained by simulating the vertical movements of a boat. The tests show that for stream velocities below 2.5 feet per second the accuracy of all three meters is significantly affected when the meters are subjected to certain conditions of vertical motion that can occur during actual field operations. Both the rate of vertical motion and the frequency of vertical oscillation affect the registration of the meter. The results of these tests, presented in the form of graphs and tables, can be used as a guide to determine whether wind and stream flow are within an acceptable range for a reliable discharge measurement from a boat.
Kallio, Nicholas A.
The vertical structure of the Daphnis wakes
When Saturn approached its equinox in August 2009 the Sun cast long shadows onto the ring-plane. Many shadows are caused by local vertical perturbations of the otherwise thin disk. The shadows at the Keeler gap edge are, for example, caused by Daphnis' gravitational perturbations. It has been proposed that these large vertical structures (more than 1 km) are caused by the inclination of Daphnis' orbit [1]. Here we show the possibility that also the ring-moon Daphnis on a non-inclined orbit is able to produce these vertical structures. We performed N-body particle simulations and found that particle collisions in the wake crests can significantly increase the vertical dispersion velocity and therefore the height of the corresponding structures. In the case of the Keeler gap edges this can lead to vertical excursions of the ring particles larger than 1 km. We compare and discuss the importance of both processes (moon inclination and particle collisions) for the vertical structure of the Keeler gap edges.
Sei�, M.; Salo, H.; Hoffmann, H.; Spahn, F.; Schmidt, J.
Sensible and latent heating of the atmosphere as inferred from DST-6 data
The average distribution of convective latent heating, boundary layer sensible heat flux, and vertical velocity are determined for the winter 1976 DST period from GLAS model diagnostics. Key features are the regions of intense latent heating over Brazil, Central Africa, and Indonesia; and the regions of strong sensible heating due to air mass modification over the North Atlantic and North Pacific Oceans.
Herman, G. F.; Schubert, S. D.; Johnson, W. T.
Vertical R&D Spillovers, Cooperation, Market Structure, and Innovation
This paper studies vertical R&D spillovers between upstream and downstream firms. The model incorporates two vertically related industries, with horizontal spillovers within each industry and vertical spillovers between the two industries. Four types of R&D cooperation are studied: no cooperation, horizontal cooperation, vertical cooperation, and simultaneous horizontal and vertical cooperation. Vertical spillovers always increase R&D and welfare, while horizontal spillovers
Gamal Atallah
Radiation induced melting of a semitransparent vertical slab of phase-change material
In this paper the results of an experimental investigation of the radiative melting of a vertical slab of semitransparent phase-change material (PCM) which results in an unstable hydrodynamic condition giving rise to natural convection fluid motion. The experiment was motivated by the need of preliminary groundwork and initiative for further investigations into this type of a phase-change problem, which is of importance in many and widely varied fields of technology. Among the applications of the melting of a vertical slab of PCM is the latent-heat solar wall used in passive solar housing. Here the use of a semitransparent material in the wall (with one transparent side through which solar energy is incident upon the material) has distinct advantages over the conventional solar wall. A fundamental understanding of heat transfer during melting, arising at least partially from the internal absorption of radiation, is of special significance in the design of such passive systems. The paper is concerned with the melting of a vertical slab of phasechange material contained in a rectangular cavity by irradiation through a transparent vertical wall of a test cell containing the material. Earlier studies, and more recently, of a similar phase-change process (in which the melting was from a heated vertical wall of the test cell rather than by radiation) have provided conclusive evidence of the influence of buoyancy-driven convection in the melt on the liquid/solid interface motion. The objective of the paper is to report on an experimental investigation of the effect of natural convection, coupled with the internal absorption of radiation, on the timewise motion of the melting front and distribution of temperature when the melting is driven by radiation rather than by contact with a heated wall.
Diaz, L.A.; Viskanta, R.
Heat transfer in microwave heating
Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, w�stite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite, which is a typical magnetic dielectric, was simulated by using an explicit finite-difference approach. It is demonstrated that the heat generation due to microwave irradiation dominates the initial temperature rise in the heating and the heat radiation heavily affects the temperature distribution, giving rise to a hot spot in the predicted temperature profile. Microwave heating at 915 MHz exhibits better heating homogeneity than that at 2450 MHz due to larger microwave penetration depth. To minimize/avoid temperature nonuniformity during microwave heating the optimization of object dimension should be considered. The calculated reflection loss over the temperature range of heating is found to be useful for obtaining a rapid optimization of absorber dimension, which increases microwave absorption and achieves relatively uniform heating. To further improve the heating effectiveness, a function for evaluating absorber impedance matching in microwave heating was proposed. It is found that the maximum absorption is associated with perfect impedance matching, which can be achieved by either selecting a reasonable sample dimension or modifying the microwave parameters of the sample.
Peng, Zhiwei
Experimental investigation on condensation heat transfer and pressure drop of R134a in a plate heat exchanger
Condensation heat transfer of R134a in a vertical plate heat exchanger was investigated experimentally. The local heat transfer coefficients are determined by means of the measured local wall temperatures. A differential energy balance model is developed for data evaluation. It is found that the correlation proposed by Shah using ? and Z factors is suitable for condensation in plate heat exchangers and is adopted to fit the measured data.
Shi, Z.-Y.; Chen, J.-P.; Grabenstein, V.; Kabelac, S.
Performance analysis of a solar-assisted ground-source heat pump system for greenhouse heating: an experimental study
This study investigates the performance characteristics of a solar-assisted ground-source (geothermal) heat pump system (SAGSHPS) for greenhouse heating with a 50m vertical 32mm nominal diameter U-bend ground heat-exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22�C, 1226 degree days heating, base: 18�C), Turkey. Based upon the measurements made
Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...
Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Detail, Vertical Cross Bracing-End Detail - Cumberland Covered Bridge, Spanning Mississinewa River, Matthews, Grant County, IN
Heat Pipes were originally developed by NASA and the Los Alamos Scientific Laboratory during the 1960s to dissipate excessive heat build- up in critical areas of spacecraft and maintain even temperatures of satellites. Heat pipes are tubular devices where a working fluid alternately evaporates and condenses, transferring heat from one region of the tube to another. KONA Corporation refined and applied the same technology to solve complex heating requirements of hot runner systems in injection molds. KONA Hot Runner Systems are used throughout the plastics industry for products ranging in size from tiny medical devices to large single cavity automobile bumpers and instrument panels.
Phoenix Refrigeration Systems, Inc.'s heat pipe addition to the Phoenix 2000, a supermarket rooftop refrigeration/air conditioning system, resulted from the company's participation in a field test of heat pipes. Originally developed by NASA to control temperatures in space electronic systems, the heat pipe is a simple, effective, heat transfer system. It has been used successfully in candy storage facilities where it has provided significant energy savings. Additional data is expected to fully quantify the impact of the heat pipes on supermarket air conditioning systems.
Effects of mesoscale convective organization and vertical wind shear on the cumulus-environment interaction
This study is made to understand the thermodynamic and dynamic aspects of cumulus-environment interaction. Specifically, the author examines (1) the similarities and differences of cumulus-environment interactions in the tropical and midlatitude convective systems (2) the impact of the presence of mesoscale circulations on the interpretation of cumulus-environment interaction, and (3) the effects of vertical wind shear on the dynamic interaction of cumulus convection with the large-scale motion. Analysis of PRE-STORM and GATE data show larger moist convective instability, large-scale forcing and vertical wind shear in the mid-latitude MCCs and squall lines than in the tropical non-squall clusters. The interaction mechanism based on the cumulus-induced subsidence and detrainment is capable of explaining most of the observed heating and drying under widely different environment conditions. The Arakawa-Schubert (A-S) quasi-equilibrium assumption is valid. Both the cumulus and stratiform cloud effects are stronger in midlatitude convective systems than in tropical systems. The heat and moisture budget results using the fine resolution SESAME data show pronounced dipole patterns in the horizontal distributions of vertically integrated heat source and moisture sink. Further analysis shows that the dipole pattern is closely related to the horizontal fluxes of heat and moisture due to mesoscale circulations. The quasi-equilibrium assumption becomes more accurate for the data resolving mesoscale circulation. The inclusion of downdrafts is required to accurately predict the cumulus heating and drying. Significant differences are found in vertical transport of horizontal momentum between the MCC and squall line. A new cloud momentum model which includes the convective-scale horizontal pressure gradient force has been developed. The application of the new cloud momentum model shows that the new model can simulate both the upgradient and downgradient transport of cloud momentum.
Wu, Xiaoqing.
Climatology of tropospheric vertical velocity spectra
Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone Delta, France; and Ponape, East Caroline Islands using 50-MHz clear-air radars with vertical beams are given. The spectra were obtained by analyzing the quietest periods from the one-minute-resolution time series for each site. The lengths of available vertical records ranged from as long as 6 months at Poker Flat to about 1 month at Platteville. The quiet-time vertical velocity spectra are shown. Spectral period ranging from 2 minutes to 4 hours is shown on the abscissa and power spectral density is given on the ordinate. The Brunt-Vaisala (B-V) periods (determined from nearby sounding balloons) are indicated. All spectra (except the one from Platteville) exhibit a peak at periods slightly longer than the B-V period, are flat at longer periods, and fall rapidly at periods less than the B-V period. This behavior is expected for a spectrum of internal waves and is very similar to what is observed in the ocean (Eriksen, 1978). The spectral amplitudes vary by only a factor of 2 or 3 about the mean, and show that under quiet conditions vertical velocity spectra from the troposphere are very similar at widely different locations.
Ecklund, W. L.; Gage, K. S.; Balsley, B. B.; Carter, D. A.
Vertical saccades in children: a developmental study.
There are no studies exploring the development of vertical saccades in large populations of children. In this study, we examined the development of vertical saccades in sixty-nine children. Binocular eye movements were recorded using an infrared video oculography system [Mobile EBT(�), e(ye)BRAIN], and movements from both eyes had been analyzed. The gain and the peak velocity of vertical saccades show an up-down asymmetry. Latency value decreases with the age of children, and it does not depend on the direction of the saccades; in contrast, the gain and the peak velocity values of vertical saccades are stable during childhood. We suggest that the up-down asymmetry is developed early, or is innate, in humans. Latencies of vertical saccades develop with the age of children, in relationship with the development of the cortical network responsible for the saccade preparation. In contrast, the precision and the peak velocity are not age-dependent as they are controlled by the cerebellum and brainstem structures. PMID:24352609
Bucci, Maria Pia; Seassau, Magali
A simple model for the design of vertical tube absorbers
The absorption of water vapor in aqueous solutions of lithium bromide is modelled for a falling-film, vertical-tube absorber. The model is based on the solution of three ordinary differential equations to calculate solution bulk and interface concentration and temperature distributions and the coolant temperature distribution. The heat and mass transfer coefficients employed in the equations are extracted from the literature. In this way, the model incorporates recent information on wavy-laminar flows. Under certain conditions, the solution exhibits instabilities in the entrance region of the absorber tube, which are corrected by the introduction of a dampening factor incorporating relevant thermophysical properties. The usefulness of the model for generating absorber performance charts is demonstrated.
Patnaik, V.; Perez-Blanco, H. [Pennsylvania State Univ., University Park, PA (United States); Ryan, W.A. [Gas Research Inst., Chicago, IL (United States)
Vertical-cavity surface-emitting lasers for flip-chip packaged vertical optical interconnects
Vertical cavity surface emitting lasers (VCSELs) have been fabricated and studied as the optical sources in a vertical optical interconnect application. The VCSELs are to replace LEDs that are currently used in a proof-of-concept demonstration. The advantages of VCSELs ares better power efficiency as sources, higher optical powers, focused beam output, monochromatic operation, and higher modulation bandwidth. The VCSELs used
Sean S. O'Keefe; William J. Schaff; Lester F. Eastman
Incorporation of vertical permeability test results in vertical miscible flood design and operation
The original analysis of the Bigoray Nisku B Pool miscible flood indicated potential coning problems related to the level of vertical permeability. This work presents the results of a vertical permeability test which were incorporated into a coning study. Additional reservoir data along with the rate information from the coning study will be used to revise the original reservoir simulation prediction and depletion strategy.
Gillund, G.N.; Kamal, M.
Reconstructing the vertical profile of humidity on the basis of the vertical profile of temperature
The vertical profile of humidity in the atmosphere is developed on the basis of the vertical profile of temperature using an empirical formula linking changes in humidity with changes in temperature and altitude. The atmosphere is divided into three layers by altitude, since the condition for the formation of humidity varies with altitude.
Bazlova, T. I.
Nation's tallest VAWT (Vertical Axis Wind Turbine) turning out the watts. [Vertical Axis Wind Turbine
This article describes the development of the tallest and most powerful windmill of its kind in the U.S. Known as a Vertical Axis Wind Turbine (VAWT), the machine is meant for testing new concepts in vertical axis turbine design. As part of its overall testing program, the turbine will supply electricity to automated water pumps used in irrigation research at
Vertical vibration analysis for elevator compensating sheave
Most elevators applied to tall buildings include compensating ropes to satisfy the balanced rope tension between the car and the counter weight. The compensating ropes receive tension by the compensating sheave, which is installed at the bottom space of the elevator shaft. The compensating sheave is only suspended by the compensating ropes, therefore, the sheave can move vertically while the car is traveling. This paper shows the elevator dynamic model to evaluate the vertical motion of the compensating sheave. Especially, behavior in emergency cases, such as brake activation and buffer strike, was investigated to evaluate the maximum upward motion of the sheave. The simulation results were validated by experiments and the most influenced factor for the sheave vertical motion was clarified.
Watanabe, Seiji; Okawa, Takeya; Nakazawa, Daisuke; Fukui, Daiki
Purification process for vertically aligned carbon nanofibers
Individual, free-standing, vertically aligned multiwall carbon nanotubes or nanofibers are ideal for sensor and electrode applications. Our plasma-enhanced chemical vapor deposition techniques for producing free-standing and vertically aligned carbon nanofibers use catalyst particles at the tip of the fiber. Here we present a simple purification process for the removal of iron catalyst particles at the tip of vertically aligned carbon nanofibers derived by plasma-enhanced chemical vapor deposition. The first step involves thermal oxidation in air, at temperatures of 200-400 degrees C, resulting in the physical swelling of the iron particles from the formation of iron oxide. Subsequently, the complete removal of the iron oxide particles is achieved with diluted acid (12% HCl). The purification process appears to be very efficient at removing all of the iron catalyst particles. Electron microscopy images and Raman spectroscopy data indicate that the purification process does not damage the graphitic structure of the nanotubes.
Nguyen, Cattien V.; Delziet, Lance; Matthews, Kristopher; Chen, Bin; Meyyappan, M.
Stochastic simulation of vertically nonhomogeneous gusts
The small-scale horizontal gust structure of detailed wind profiles along the vertical in the first 20 km of the atmosphere is a vertically nonhomogeneous process. A linear stochastic model was developed based on the process covariance function. This model was formulated through the use of a scaling hypothesis which transforms the nonhomogeneous gust process into a nondimensional gust process which is homogeneous in a nondimensional gust height coordinate. The velocity scaling parameter for the gust process is the gust standard deviation, and the length scale used to nondimensionalize the altitude is the vertical space lag associated with the first zero of the gust covariance function. State space theory was used to derive a digital filter from the model, which can be readily used to simulate gusts for space vehicle design applications.
Fichtl, G. H.; Perlmutter, M.
Liquid storage tanks under vertical excitation
Until recently, the hydrodynamic effects on liquid storage tanks induced by an earthquake excitation were basically treated for the horizontal component of the earthquake. Recent studies, however, showed that the hydrodynamic effects due to the vertical component of an earthquake may be significant. In these studies the tank is assumed to be fixed at the bottom. This paper is concerned with the hydrodynamic behavior of liquid storage tanks induced by vertical earthquake input excitation. First, the fluid-tank system is treated as a fixed-base system and a simple formula is obtained for the coupled fluid-structure natural frequency. Second, additional interaction effects due to the foundation flexibility on the fluid-tank system are investigated. It is concluded that the foundation flexibility may have a significant effect on the hydrodynamic behavior of the liquid storage tanks under a vertical ground shaking.
Philippacopoulos, A.J.
Thermal analysis of the vertical bridgman semiconductor crystal growth technique. Ph.D. Thesis
The quality of semiconductor crystals grown by the vertical Bridgman technique is strongly influenced by the axial and radial variations of temperature within the charge. The relationship between the thermal parameters of the vertical Bridgman system and the thermal behavior of the charge are examined. Thermal models are developed which are capable of producing results expressable in analytical form and which can be used without recourse to extensive computer work for the preliminary thermal design of vertical Bridgman crystal growth systems. These models include the effects of thermal coupling between the furnace and the charge, charge translation rate, charge diameter, thickness and thermal conductivity of the confining crucible, thermal conductivity change and liberation of latent heat at the growth interface, and infinite charge length. The hot and cold zone regions, considered to be at spatially uniform temperatures, are separated by a gradient control region which provides added thermal design flexibility for controlling the temperature variations near the growth interface.
Jasinski, T. J.
Heated Goggles
The electrically heated ski goggles shown incorporate technology similar to that once used in Apollo astronauts' helmet visors, and for the same reason-providing fogfree sight in an activity that demands total vision. Defogging is accomplished by applying heat to prevent moisture condensation. Electric heat is supplied by a small battery built into the h goggles' headband. Heat is spread across the lenses by means of an invisible coating of electrically conductive metallic film. The goggles were introduced to the market last fall. They were designed by Sierracin Corporation, Sylmar, California, specialists in the field of heated transparent materials. The company produces heated windshields for military planes and for such civil aircraft as the Boeing 747, McDonnell Douglas DC-10 and Lockheed L-1011 TriStar.
Radiative Heating Profiles for Tropical Cloud Regimes
Radiative heating is important for its effects on atmospheric circulation and cloud evolution in addition to its central role in influencing the atmospheric temperature structure. The vertical distribution of radiative heating is determined by the vertical profile of gases such as water vapor, ozone and CO2 as well as by clouds. The Atmospheric Radiation Measurement (ARM) program operates sites around the world which provide measurements of surface radiative fluxes and various measurements of the atmospheric state that effect surface fluxes. Continuously operating millimeter cloud radars at each site provide the means to derive vertical profiles of cloud properties. In previous work, we have used these cloud profiles in combination with profiles of temperature and humidity from radiosondes to calculate radiative flux profiles using a 4-stream radiative transfer model at the three tropical ARM sites: Manus, Nauru, and Darwin. In the current study, we will use the vertical profiles of cloud properties at these sites to segregate the data into distinct cloud regimes. By compositing radiative heating profiles in different regimes, we will define characteristic radiative heating profiles of each cloud regime. Analysis of the data in terms of cloud regime provides datasets which can be more easily compared with climate model results.
Mather, J. H.; McFarlane, S. A.
Vertical stability, high elongation, and the consequences of loss of vertical control on DIII-D
Recent modifications to the vertical control system for DIII-D has enabled operation of discharges with vertical elongation {kappa}, up to 2.5. When vertical stability is lost, a disruption follows and a large vertical force on the vacuum vessel is observed. The loss of plasma energy begins when the edge safety factor q is 2 but the current decay does not begin until q {approximately}1.3. Current flow on the open field lines in the plasma scrapeoff layer has been measured and the magnitude and distribution of these currents can explain the observed force on the vessel. Equilibrium calculations and simulation of this vertical displacement episode are presented. 7 refs., 4 figs.
Kellman, A.G.; Ferron, J.R.; Jensen, T.H.; Lao, L.L.; Luxon, J.L.; Skinner, D.G.; Strait, E.J.; Reis, E.; Taylor, T.S.; Turnbull, A.D. (General Atomics, San Diego, CA (USA)); Lazarus, E.A. (Oak Ridge National Lab., TN (USA)); Lister, J.B. (Centre de Recherches en Physique des Plasmas, Lausanne (Switzerland))
Performance tests of the 1MWt shell-and-tube heat exchangers for OTEC
Final test results are reported for the five 1 MWt shell-and-tube heat exchangers tested at Argonne National Laboratory. These five heat exchangers are the Union Carbide flooded-bundle evaporator, the Union Carbide sprayed-bundle evaporator, the Union Carbide enhanced-tube condenser, the Carnegie-Mellon vertical fluted-tube evaporator, and the Carnegie-Mellon vertical fluted-tube condenser. Performance parameters measured include the overall heat transfer