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Problem Statement: What is the meaning of the surface value (Surf/unit(eff)) on the TEMA data sheet? | Solution: The surface value from the TEMA data sheet (Surf/unit(eff)) is the effective area per unit of heat exchanger. If you have a certain number of parallel shells (x) and a certain number of series shells (y), the total area will be:
Area = x * y * (surf/unit(eff))
The effective surface area (i.e. area of all heat exchangers) can be found in Results / Thermal / Hydraulic Summary / Performance / Overall Performance.
Keywords: Surf/unit(eff), Tasc+, Area
References: None |
Problem Statement: When exporting the results of an EDR case into an Excel template by going to File | Export to, users have two options.
a) One is to choose Excel using Specified Template, where users need to manually navigate to the directory where the desired template is located, and select the relevant template, as described in | Solution: 124571. This is not always convenient, when frequently using a particular template.
b) The other one is to choose Excel using Default Template, where users need firstly to set a default template. Then this template will be automatically used every time when users select Excel using Default Template, without having to navigate and specify.
ThisSolution describes how to set the default template location as described in b) above.Solution
To set the default Excel template for exporting purpose, select from the program menu, Tools | Program Settings | Files tab. You will see three sections, where the middle one, Excel templates is the one we need to set.
Firstly, set the Application, which determines the template for a particular EDR application.
Secondly, click the browser button and navigate to the location of the desired template. Normally it will be C:\Program Files\AspenTech\Aspen Exchanger Design and Rating V7.1\Excel Templates\, depending on the directory where the program has been installed and the version of the program.
Click OK.
Now when you implement the exporting by going to File | Export to and select Excel using Default Template, the template as set above will be automatically used as default template.
Keywords: Export, Excel, Template, Default.
References: None |
Problem Statement: Why is there a pressure rise instead of a pressure drop in my heat exchanger? | Solution: This scenario is possible if there is a significant loss of velocity of the fluid inside the heat exchanger. The phenomenon is typically observed in condensation processes, since the fluid velocity reduces significantly as the vapor condenses. Bernoulli's equation implies that a loss in velocity head causes an increase in the pressure head. When this rise is more than pressure drop, you will observe a net pressure rise instead in the heat exchanger.
Keywords: pressure, rise, negative, drop
References: None |
Problem Statement: Sometimes I notice that the duties are different between Aspen Tasc+ and Aspen TASC when using the fixed mode for a thermosyphon. | Solution: In Aspen TASC or Aspen Tasc+, the thermosyphon calculations have two modes of operation: Fixed flow and Find flow.
1. In Fixed flow, Aspen TASC and Aspen Tasc+ determine the pressure losses in the exchanger and associated pipework. Fixed flow will result in a physically un-real pressure imbalance around the thermosyphon circuit. This imbalance is reported with the thermosyphon results. Thermosyphon stability results should be treated with caution for these calculations where there is a significant pressure imbalance.
In Fixed flow the program will use the flowrate supplied and then present a pressure drop imbalance around the system.
There are differences in the way that Aspen TASC and Aspen Tasc+ operate when in the Fixed mode.
In Aspen TASC, when fixed mode is set, Checking calculations are performed based on the outlet conditions supplied for the exchanger, where Aspen TASC reports back an area ratio. These outlet conditions are then also used in the outlet circuit to determine the pressure drops.
If Aspen TASC reports that the area ratio greater than 1, then heat exchanger could achieve a greater duty then that assumed.
In Aspen Tasc+, when fixed mode is set, Simulation calculations are performed, so the program calculates the outlet conditions for the exchanger based on the flowrate given. If the flowrate is not actually given in the file, it is calculated from the heat duty and the inlet and outlet conditions. Therefore the run is comparable to running Aspen TASC in fixed mode when the area ratio is close to 1.
Therefore the difference is in the way that the fixed flow calculations are performed between the two versions, where Aspen TASC does checking calculations and reports the Area ratio to indicate if the exchanger is under/over surfaced, while Aspen Tasc+ performs simulation calculations to give the actual performance of the heat exchanger. These results will only be comparable if the area ratio in Aspen TASC is very close to 1.
2. In Find flow, Aspen TASC and Aspen Tasc+ find the thermosyphon stream flowrate, consistent with the driving head of liquid and the pressure losses in the exchanger and associated pipework. Here the cold (thermosyphon) stream mass flowrate you specify is taken as an estimate only.
When in Find flow, the thermosyphon flowrate provided is taken as an estimate, where the program will then calculate the thermosyphon flow by performing a pressure drop calculation around the inlet circuits (from distillation column to the heat exchanger) the heat heat exchanger and the outlet circuit (from heat exchanger to distillation column). The program neglects any frictional pressure drop inside the column as the diameter is probably large and also the gravitation head due to the vapour. The program iterates by changing the flowrate and the heat transfer until the sum of the pressure drops of these components is be zero.
With find flow you should note that the results between both versions should be similar as both use simulation calculations for the heat exchanger and determine the thermosyphon flowrate by matching the pressure drops around the circuit.
Note the default setting is Find flow.
Keywords: Thermosiphon
References: None |
Problem Statement: There are three issues with the legacy HTFS programs and Vista and for that matter Windows XP if you are a restricted user.
By default Vista users are all restricted users, unless you specifically designated as an administrator | Solution: 1) If user tries to run the legacy products and select an example file which we distribute and place in a folder under Program Files. The program will not be able to open the file as writable. We have noted in the Known Issues that the user should copy these files to a non-restricted folder before trying to run them.
2) HTFS legacy products have an option to set preferences for the program to locate Component and Stream databank files. These settings are made in an INI file which is located under C:\WINDOWS . A restricted user can change them, but when the UI is closed and reopened, the changes he made will not be there. An administrator would have to make the change.
3) SBANKI and CBANKI files will have to be located somewhere other than in a restricted access folder in order for a user to add components or streams to them.
The key item to point out is that Vista has severely restricted what the average normal machine user can do. He cannot change the registry, he cannot access files in the Windows system folder or any files in that may reside in folders under Program Files. Our programs have typically done this in the past.
For users converting to Vista, I would suggest that they try to set themselves up as Administrators for their machines. They may also have to turn their User Access Control (UAC) off.
If they cannot do that, then they will have to have their administrators set up their preferences so that the programs do not access files under Program Files.
An ADMIN user must install the programs
Keywords: User Access Control,HTFS 2006.5,Windows Vista,Windows 7,Windows Xp
References: None |
Problem Statement: How to download files from aspenONE Exchange? | Solution: 1. Click on the Icon for the app that you are interested in. For example, the 'Sulzer Select' tool:
2. To begin downloading, click on the play button
3. You will be prompted to enter your support site credentials if you have not already
4. The file will either automatically download or you will be prompted to accept the download agreement. For a download agreement this is what the buttons mean:
a. Print - Use this option to print a copy of the download agreement.
b. Accept and Continue - Use this option to accept the download agreement and to download the selected App.
c. Decline - Use this option not to accept the download agreement. If you do not accept the download agreement, you cannot download the selected App.
5. Most of the downloads are free, but some may prompt you to pay. If the App requires a payment, you are directed to a secure Web page to provide credit card information. After completing the purchase on the secure Web page, return to aspenONE Exchange and open or run the App again.
Keywords: Download, Exchange, aspenONE
References: None |
Problem Statement: General guidelines for avoiding vibration at the design stage. | Solution: Avoiding Vibration at the Design Stage.
Make certain all possible duties are investigated: plants are often operated at different temperatures and pressures, even with different fluids, for example during catalyst reduction or during cleaning. Designers should note that many units are operated at flows beyond that specified. When plant operation is changed or up-rated, it will be necessary to have the heat exchanger design re- examined.
Ensure that the design is satisfactory for conditions encountered during start up and shut down: some failures occur because of prolonged operation at a critical condition during part load.
Ensure that heat exchangers are included in all hazard/operability studies: in this way abnormal operation will be routinely considered.
To produce designs with a low susceptibility to vibration, single segmental baffles should not be used. Instead to reduce cross flow velocities, double segmental baffles or J-shells should be used. In extreme cases designs with no tubes in the window or cross flow units should be used. These measures should be used in combination with low fluid velocities.
U-tube designs: avoid having the flow from the inlet nozzle impinge directly onto the bend.
U-tube designs: consider the provision of supports by the use of stiffening bars in the U-bend section. This alters the natural frequency. This can be conveniently done with square and rotated square tube layouts, but is difficult with triangular layouts.
U-tube designs: it is advisable to design the U-bend region so that flow velocities are as low as practicable. Provision of extra tube support should not be a justification for using a higher than necessary fluid velocity in this area, since the gain in overall heat transfer will be small and the risk of producing vibration large.
Ensure that inlet nozzles are not undersized: the use of perforated impingement plates is sometimes possible to avoid high local impingement velocities. When using an impingement plate do not have large escape velocities: larger shells are often needed to accommodate an impingement plates satisfactorily.
With condensers, provision of a vapor belt is a useful way of reducing inlet velocities and obtaining uniform velocity distribution at the inlet. However the cost of installing a vapor belt is high.
Use sealing strips if accurately known fluid velocities are essential to promote long life: sealing strips should not be too close to the baffle cut line. It should be noted however that sealing strips can give rise to large local velocities.
Avoid making the end spans any longer than necessary.
If long spans at inlet and outlet are unavoidable for any reason, provide additional support for the window tubes near the mid-point of the long span.
Partial baffles are widely used to correct problems in inlet and outlet zones: their use is recommended when impingement plates are necessary (five rows deep).
Avoid liquids being trapped at baffles and so causing high local velocities: adequate but not excessive drain holes (notches) must be provided.
There is some evidence that certain tube layout patterns are more conducive to the formation of standing acoustic waves than others. The rotated square tube layout should be avoided on this account, if possible, when the shell side fluid is gas or vapor.
Consider the use of solid bars instead of tubes in the first two tube rows if problems are indicated during design or encountered during operation.
Avoid, where possible, design with tubes located near to Hogging Jets in condensers.
Do not use the minimum number of baffles in kettle and horizontal thermosiphon reboilers: this is false economy. Particular difficulties can rise in H-shell horizontal thermosiphon reboilers: here a tube support plate should always be placed at the mid point of the tubes.
Natural frequencies are lowered by the presence of compressive stresses in the tubes. The effect will be to render the tubes more susceptible to both fluid-elastic instability and vortex shedding resonance. Designs should therefore be examined critically to see whether compressive stresses arise. If, for any reason, some compressive stress is unavoidable, its effect on the natural frequencies should be calculated. These natural frequencies should then be used in any assessment of vibration characteristics.
Avoid sharp bends in inlet pipework: major swirl can cause excessive velocities.
Keywords: avoid, vibration, design stage
References: None |
Problem Statement: How can I add or remove an application from an Exchanger, Design and Rating (EDR) file? | Solution: Aspen EDR program has the option to add or remove a number of applications within the same file.
Adding an application -
An EDR file can be made to have more than one application in it. What this means is that if you have an EDR file with one application and if you wish to add more applications in the same file, you click on File | Add application and you see a list of options (see below) that you can select and press OK.
When you select and press OK, you will see a number of windows being generated inside the EDR program and this will enable you to access various parameters of any of these applications. You can also save the file and it retains all the applications that have been added.
Loading an EDR file which contains more than one application -
When you load an EDR file which contains more than one application, you see a dialog box (see below)
You can see here how many applications that exist within the EDR file and select the ones (you may choose all or just one) you wish to load and press OK. Please note that this is just an option to load or not to load the application and it its entirely different from removing an application from the program which is explained below.
Removing an application -
Load the EDR file, Click on File | Remove Application, you will see a small window (see below). Select the application(s) you wish to delete and press OK. Save the file and you will not see that particular application in BOLD when loading it next time.
Keywords: Add, Remove, Application
References: None |
Problem Statement: There are various ways in which user can arrange the multiple shells of the exchanger to obtain the optimum heat transfer and pressure drop results. User can choose to have tubeside flow in series or parallel regardless to the flow pattern selected for shellside flow.
Aspen Shell and Tube Exchanger can handle up to 12 shells in series and up to 50 in parallel.
When the Advanced calculation mode is set, it is possible to set different flow paths through the shells for the tube and shell side as described below. | Solution: In Aspen Exchanger Design & Rating (EDR), you can specify the number of shells in series or parallel under Input | Exchanger Geometry | Shell/Heads/Flanges/Tubesheets | Shell/Heads tab. Since multiple shells in series are usually needed due to temperature range overlap of the streams, an overall Counterflow is the only thermodynamically possible option.
If no temperature range overlap exists, you can sometimes benefit by modeling the flow of one side to be in a series (to achieve good heat transfer) and the other side to be in parallel (to achieve a low pressure drop); to model these flows, use the options Shell side in parallel, tube side in series or Tube side in parallel, shell side in series. You can select the Overall flow for multiple shells Input | Exchanger Geometry | Shell/Heads/Flanges/Tubesheets | Shell/Heads tab. Please note that this feature of selecting flow pattern is only available in EDR v7.2.1 and onwards.
From Input | Exchanger Geometry | Shell/Heads/Flanges/Tubesheets | Shell tab, the overall flow for multiple shells can be set.
The options available are;
Counter current
Since multiple shells in series are generally needed due to temperature range overlap of the streams, an overall Counterflow is the only thermodynamically possible option.
Co current
You might also benefit by using overall co-current flow, which gives a large temperature difference at inlet, and a small one at outlet, by using the Co-current option.
Shellside parallel, tubeside series
If no temperature range overlap exists, you can sometimes benefit by modelling the flow of one side to be in parallel (to achieve a low pressure drop) and the other side to be in a series (to achieve good heat transfer
Tubeside parallel, shellside series
If no temperature range overlap exists, you can sometimes benefit by modelling the flow of one side to be in parallel (to achieve a low pressure drop) and the other side to be in a series (to achieve good heat transfer
Regardless of the flow pattern in multiple shells, you need to enter in the total flow rate for shellside & tube side in Process Data tab. The Program will automatically evaluate the flowrate, temperature, pressure conditions through individual shells for both sides. Once you have run the case, you can also check the individual shell conditions under Results | Thermal/Hydraulic Summary | Performance | Inter-Shell Conditions tab as shown below:
When there are N shells in series, shell 1 always has the shell side inlet. The tube side stream enters in shell N when there is overall counterflow. In other flow configurations, the tube side stream enters in shell 1.
If in addition to N shells in series, it is specified that there are M shells in parallel, then M refers to the series flow stream(s). If it is specified that one side is connected in parallel, then overall there are M times N parallel flows of this stream.
Keywords:
References: None |
Problem Statement: How can I transfer data from Aspen Shell and Tube Exchanger to Aspen Air Cooled Exchanger or Aspen Plate Exchanger? | Solution: Aspen Exchanger Design & Rating (EDR) has an inbuilt transfer feature that can be used to transfer the process and property data from Aspen Shell and Tube program to Aspen Air-cooled or Aspen Plate exchanger or vice-versa. One EDR file can have multiple applications in it and user has the option to load these applications every time within the EDR file.
Here are the steps on how to perform this transfer function and create Aspen Air Cooled Exchanger or Aspen Plate Exchanger program internally within Aspen EDR using Aspen Shell and Tube Exchanger data -
1. Open Aspen EDR program, load the .EDR file.
2. Click on Run | Transfer, and select the desired program name. If you have loaded Shell and Tube file, then you will have three options - Shell & Tube Mechanical, AirCooled Exchanger and Plate Exchanger. If the EDR file already contains an application of above three programs, then the user can select 'Clean up selected application(s) before transfer'. This will clean up all the data existing in the selected applications and will transfer the new data over.
3. Selecting Air Cooled Exchanger and Plate Exchanger will open up two more windows inside Aspen EDR and these two will have process and property data from the original Shell and Tube file. Please note that with Air Cooled Exchanger, it will only transfer the tubeside process and property data.
4. When you have saved this EDR file, next time you load the EDR file you will see a dialog box with list of options (see below an example). There are few options in Bold which means that this .EDR file contains all these applications and you have the option (by selecting) to load a particular application(s).
Keywords: Transfer, data
References: None |
Problem Statement: A Process Simulator File (PSF) can be used to transfer data to the Exchanger Design and Rating (EDR) suite of programs, where the file can contain both process and physical property data. This | Solution: describes a methods to generate a PSF file using Aspen Plus.Solution
From an Aspen plus simulation that contains a HEATX block, with heating/cooling curves generated using the HXDESIGN property set, the HTXINT utility can be used to generate a PSF file.
Creating the Property Set in Aspen plus
1. First, inside Aspen Plus, you need to create heating/cooling curves that use the property set HXDESIGN as the set of properties to be reported.
The HXDESIGN Prop-set is present in most Aspen Plus templates, so if you started your simulation by using one of the templates (e.g. General with Metric Units) you will already have this property set. Look in the Properties > Prop-Sets folder in the Aspen Plus data browser to check this. The HXDESIGN property set contains all of the properties needed for heat exchanger design e.g. viscosity, thermal conductivity, heat duty and so on.
If you have not started your simulation with one of the standard templates and do not have the HXDESIGN property set, you can use File > Import, change the file type to Template and import, say, the General with Metric Units template. This will normally be located in directory:
C:\Program Files\AspenTech\Aspen Plus V7.x\Gui\Templates\Simulations
2. Next either create a new heat exchanger (HEATX) block or use an existing one in your Aspen Plus simulation. The heat exchanger block will probably be using the default Shortcut calculation mode which is ok.
3. Within the HEATX block, change to the Hot Hcurves folder and click on New to create a Hot stream curve.
Accept the default ID of 1.
4. The property curves are generated across a range of 10 conditions. The default independent variable is Heat Duty i.e. it generates properties across a range of equal duty intervals. This is usually the best option to use. The curves always include the starting & end temperatures, and also the dew & bubble temperatures if these fall within the temperature range. If required, from the ?pressure profile option? various pressures level can be set for the property curve. Switch to the Tab called Additional Properties.
Move the HXDESIGN property set from the left pane into the right pane called Selected property sets.
5. Click on the Next button (N->) to run the simulation. Then return to this Hot Hcurves folder and go to the Tab called Results to see the Hot stream property curves.
6. If you also want the Cold side properties to be used in Exchanger Design and Rating (EDR) repeat the above process but set up the property curves in the Cold HCurve folder.
7. You can set up these property curves in multiple HEATX blocks (also in Column Condensers & Reboilers, and in HEATER blocks).
8. Finally, exit from Aspen Plus and save your simulation as a backup (*.bkp) file.
From File > Export set the Save as type to 'Summary Files (*.sum)' and give a name.
Running the HTXINT Utility
You then run the HTXINT utility program which generates a process simulator file (*.psf) for EDR programs. To run the interface program HTXINT, you need to open an Aspen command window (DOS...) with Start> Programs> AspenTech> Aspen Engineering Suite> Aspen Plus V7.x> Aspen Plus Simulation Engine. In the command window, use the DOS command (cd) to move to the folder where the bkp file has been saved
e.g. cd C:\Aspen.
At the DOS prompt, type:
HTXINT name of the sum file without the extension
Then follow the prompts. You will be asked to select from a list of blocks which have property curves. - this is an example of a run:
C:\Aspen> htxint psf_example
+
+ + +
+ + +
+ + + + +
+ + + + + + + + +
+ + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + +
+ + +
+ + +
+ + + HTXINT Heat Exchanger Program Interface
+ + + Copyright (c) 1996-2002 Aspen Technology, Inc.
+ + + All rights reserved.
+
Enter ? at any prompt for help.
Please enter the required interface. (B-JAC, HTFS, M-HTFS or HTRI) > M-HTFS
Please select the units to display the data. (SI, ENG or MET) > SI
Please enter the output file name. (Default is psf_example.psf)
> test
File C:\My Folders\Solution\test.psf opened for output.
The following blocks have Hcurves.
+
Keywords: None
References: None |
Problem Statement: What do the nozzle escape area and bundle entrance/exit areas mean? | Solution: The nozzle escape area is the area through which the nozzle flow enters the shell, either directly into the bundle or into the space between the nozzle and the bundle.
The bundle entrance area is the area available for the flow to leave the the inlet nozzle escape area and flow into or around the bundle. Equivalent definitions apply to exit.
The nozzle escape area is primarily the cylinder between the nozzle and the bundle. If there is no impingement plate, the flow area through the top row of tubes and within the circular projection of the nozzle, is added to this. The bundle entrance/exit area, by contrast, depends on the width of the chord across the top/bottom of the bundle, and the length of the inlet/outlet end space. It is reduced by the area of the impingement plate, if any, and by the area of tubes in the top row. The open space within the first baffle cut can be added to this.
Sometimes, the following warnings may be issued by the program.
If it is still in the design stage, a user can understand the various options by starting with fewer specifications in the program input. The program will use defaults for tube removal under nozzles, open spaces around the bundle, end lengths and impingement plate size. A user can even omit the nozzle sizes, and the program will design these (even in Simulation mode). A number of these options involve fewer tubes in the bundle.
If the exchanger already exists, the onlySolution is to remove some tubes in the row(s) adjacent to the nozzles - maybe replacing them by impingement rods. There certainly needs to be some space adjacent to the inlet/outlet nozzle. Sometime, the TEMA limit for two phase flow is selected even when a very small amount of liquid is present. There is the risk of impingement damage by high velocity liquid carried by the vapour. An exchanger should not be operated too far away from the limit.
In the cases where the liquid amount is very small, a user can consider the possibility of spliting the phases and use separate exchangers. A user can also consider using separate liquid and vapor nozzles. Adjusting baffle spacing to get large inlet and outlet end spaces may also help.
Keywords: Nozzle escape area, bundle entrance area, bundle exit area.
References: None |
Problem Statement: What is the definition of the total, effective and required area and the difference between U clean, U dirty and U service? | Solution: The total area of the heat exchanger is determined by the PI (3.14) * Tube Outer Diameter * Tube length * Number of tubes * number of shells.
The effective heat transfer area is the area available for heat transfer (this is also often referred to as the actual area). This is the total area minus areas which are not available for heat transfer, which include tube length within tubesheets, tube projections beyond tubesheets and tube length beyond blanking baffles etc.
The required area is that heat transfer area which would be required in order to achieve the required duty, given the calculated overall coefficients and the temperature difference.
U clean: Overall heat transfer coefficient (excluding fouling resistances) predicted by Aspen Shell & Tube based on the fouling resistances specified and referred to the required area. Please note that the specified fouling resistances may affect the wall surface temperature and therefore the coefficient.
U dirty: Overall heat transfer coefficient predicted by Shell & Tube with fouling resistances included, and referred to the required area.
U service: In Checking and Design modes, this is the overall heat transfer coefficient which corresponds to the heat load specified by the user and the effective surface heat transfer area, i.e. U service = (Specified Heat Load) / (MTD * Effective heat transfer area).
In Simulation mode the duty (and outlet temperatures) are determined by Shell & Tube. Therefore the required area is the same as the effective heat transfer area (and actual area).
The area ratio is given by:
Area ratio = Effective heat transfer area / Required area
and also
Area ratio = U dirty / U service
Keywords: Duty, total area, effective heat transfer area, required area, clean coefficient, dirty coefficient, service coefficient, area ratio
References: None |
Problem Statement: Vortex shedding is a lock-in effect, caused by the periodic shedding of vortices from the tubes and can lead to damaging tube vibrations if it occurs at the tube natural frequency. This can cause substantial vibration in liquids, but only negligible vibration in gases (unless the gas has a high density and velocity). However, vortex shedding may become important in gases if it is reinforced by another tube vibration mechanism which happens to occur at the same flow condition. Such reinforcement may come from acoustic resonance. | Solution: In order to check for the possibility of vibration due to vortex shedding, the program calculates the vortex shedding frequencies (fvs) and outputs the ratios of these to the natural frequencies (fn).
Some general attempts to avoid vortex shedding:
Alter the vortex shedding frequency by changing (increasing or decreasing) the flow velocity.
Alter the tube natural frequency (increase or decrease) by changing the span lengths or the tube diameter. Changing the tube wall thickness has almost no effect.
Increase the damping. This will reduce the amplitude of any vibration which does occur, and therefore render it less damaging.
Keywords: Vortex shedding, vibration problem, avoid
References: None |
Problem Statement: Should I click Yes after receiving the error message about exceeding max disk space for Aspen Exchange Design & Rating temporary files? | Solution: By clicking Yes, the cache in memory is cleared but the actual temporary files are not deleted.
Keywords: EDR temporary files
cache
References: None |
Problem Statement: How is the width of a pass partition lane specified in Aspen Shell & Tube Exchanger? | Solution: A tube bundle can have multiple passes where the Pass layout can set as mixed (H), quadrant or ribbon. This will mean that there will be pass partition lanes, which further depends on the orientation of the pass layout. Users can select these options under Input | Exchanger Geometry | Bundle Layout | Layout Parameters tab.
Based on the layout and its orientation, you can specify the horizontal / vertical pass partition width under Input | Exchanger Geometry | Bundle Layout | Layout Limits/ Pass lanes tab. The number you type in here is the distance between tube edge of one pass to the tube edge surface of the adjacent pass. See below in the diagram, where the horizontal and vertical pass partition width are shown and marked in 'Red'
Keywords:
References: None |
Problem Statement: Two phase flow in a vertical tube can adopt many geometric configurations of the distribution between the liquid and gas phases, which are commonly known as ?flow patterns? or ?flow regimes?.
When subcooled liquid flows through a vertical tube heated with a constant heat flux, the heat transfer coefficient varies along the length of the tube and is related to the changing structure of flow pattern within the tube.
At the entrance to the tube the subcooling of the liquid is such that nucleation does not occur so that the heat is transferred by single-phase convection. As the liquid moves up the tube the temperature of the bulk fluid gradually increases.
Boiling commences when the local wall temperature reaches the superheat temperature required to activate nucleation sites, generating bubbles to give incipient boiling. In the case of onset of boiling under subcooled conditions, for a short distance beyond this point, bubbles may drift into and collapse in the still subcooled liquid. As the saturation temperature of the bulk fluid is approached, enough bubbles are generated to populate the whole of the test section resulting in bubble flow. The increasing number of bubbles leads to coalescence and the transition from bubble to plug flow, where there are large plugs of vapour (with cross sectional area approaching that of the tube) and liquid interspersed. However, if the onset of boiling occurs under conditions of superheated bulk liquid, then the vapour generation rate may be such that bubble flow may not exist, with a sudden transition to plug flow.
Further increasing the quality leads from plug flow to annular flow, where the liquid is dispersed as a film at the tube wall with some entrained droplets in the vapour core. Generation of vapour can take place as a result of bubble formation at nucleation sites and also by direct vaporization from the vapour/liquid interface. Liquid is also lost from the film by entrainment due to either the ejection of droplets when the bubble growing from the nucleation site burst through the film or by tearing off of droplets from the tips of surface waves. However, deposition of droplets from the vapour core to the liquid film opposes the rate of entrainment. The efficiency of heat conduction through the liquid film becomes greater as the quality increases along the tube due to thinning of the film, with a point reached where the temperature driving force is sufficiently reduced, such that vapour nucleation is suppressed.
Eventually the liquid thickness decreases to form localised dry patches on the tube wall, resulting in a large increase in the wall temperature. Beyond this point the flow pattern changes to liquid droplets dispersed in a vapour core and is commonly referred to as the ?liquid deficient region?, where depending upon the magnitude of the wall temperature the droplets may or may not ?wet? the tube wall. The entrained droplets within the vapour core vaporize relatively slowly and the vapour may be considerably superheated before the last droplets disappear. | Solution: In a heated tube the heat transfer and pressure drop are both dependent upon the flow pattern. Therefore, to predict these reliably, knowledge of the prevalent flow pattern is required. Flow patterns may be predicted from either;
Empirical flow pattern maps: Data collected from flow pattern observations may be presented in terms of flow pattern maps, where a two-dimensional plot attempts to separate the flow patterns into particular areas.
Theoretical flow pattern maps: To construct a theoretical flow pattern map, the mechanisms that cause the transition between successive flow patterns must be identified and equations generated to account for both the physical properties and tube geometry.
From the Exchanger Design and Rating (EDR) program for Aspen Shell and Tube Exchanger, Aspen Air Cooled Exchanger and Aspen Fired Heater the flow patterns within the tubes are determined and can be found from:
Shell and Tube: Results | Calculation Details | Analysis along Tubes | Interval Analysis tab
Air Cooled: Results | Calculation Details | Interval Analysis - Tube Side | Pressure Change tab
FiredHeater: Results | Calculation Details | Stream Details | Stream x tab
For vertical upflow in tubes the flow pattern map of Hewitt and Roberts (1969) is used, where the superficial momentum flux of the two phases ( ) are plotted.
For vertical downflow in tubes the flow pattern map of Golan and Stenning (1969-70) is used, where the superficial gas velocities are plotted.
Golan, L.P and Stenning, A.H. (1969-70) ?Two Phase Vertical Flow Maps? Proc. Inst. Mech. Eng., Vol. 184, Pt. 3c, pp. 108-114.
Hewitt, G. F., and Roberts, D. N. (1969). ?Studies of Two-Phase Flow Patterns by Simultaneous X-ray and Flash Photography? AERE-M 2159.
Keywords: flow map, flow pattern, flow regime
References: None |
Problem Statement: Exchanger Design and Rating module crashes when started up with user level authority but works well when logged in to run as Administrator. | Solution: Exchanger Design and Rating software will need to access the Temp folder, if the folder is user protected, e.g. no full administrative access, it will crash the EDR from running. The reason is the software utilizes the temp folder for temporary caching.
In Windows 7 or Vista OS, look for this folder instead, C:\Users\public.
Provide full administrative rights for the users to access these folders.
Keywords: Administrative, Temp Folder, Users, Public, Crashing, Access, Exchanger Design & Rating Module, EDR
References: None |
Problem Statement: Why is there a difference in heat coefficients and heat transfer rates between V7.3.2 and V8.0? | Solution: The change is caused because was added friction component in the shell between the baffles in V.8 follow by a change in shell side flow fractions
The change in coefficients between V7.3.2 and V8.0 is caused by adding friction with the shell between the baffles in V.8 follow by a change in shell side flow fractions.
For V8.0, the friction for the “E” stream (Baffle OD-Shell ID leakage) was increased for laminar flows by adding in friction with the shell between the baffles.
This increase resulted in a smaller Baffle OD – Shell ID flow fraction and a larger Cross flow fraction in V8.0, leading to the higher heat transfer coefficients.
The dirty transfer rate is calculated using the fouling resistance from the input while the clean transfer rate is calculated assuming zero fouling with all other conditions being the same.
The equations that calculate heat transfer rates (for either clean or dirty condition) calculations are based on a point-by-point integral method using various correlations depending on geometry (shell side, tube side, cross flow, window flow, different flow regimes (Laminar and turbulent), evaporation, condensation and boiling.
Keywords: heat coefficients, heat transfer rates, friction
References: None |
Problem Statement: How does Aspen Shell & Tube Exchanger calculate the cleaning factor? | Solution: As per the HTFS handbook,
Aspen Shell & Tube Exchanger calculates fouled and clean overall heat transfer coefficient and is displayed in Results Summary->Overall Summary sheet.
Keywords: Fouling resistance, Cleanliness factor, heat transfer coefficient
References: None |
Problem Statement: How do I view the Aspen Exchanger Design & Rating browser in expanded view by default? | Solution: From the Tools | Program Settings under the UI Options 1 select Show browser in expanded view to view the EDR browser by default in the expanded view.
Keywords: EDR browser, expanded, view
References: None |
Problem Statement: What is the Definition of Baffle Cut for Single and Multi Segmental Baffles in a heat exchanger. | Solution: This value is the amount of the Transverse Baffle that is cut away expressed as a percentage of the Shell Inside Diameter. The baffle cut range depends on the baffle type:
Single Segmental Baffles
With Single Segmental there is a single baffle style: A one-piece baffle with an Outer Baffle Cut Y
Double Segmental Baffles
With Double Segmental there are two styles of baffle:
1) A two-piece baffle with an Inner Baffle Cut X.
2) A one-piece baffle with an Outer Baffle Cut Y.
Input for Baffle Cut on Input | Exchanger Geometry | Geometry Summary | Baffle Cut (% D) is the outer Cut Y for the double segmental baffles. Inner Cut can be specified at Input | Exchanger Geometry | Baffles / Supports | Baffles under Baffle cut % - inner / outer / intermediate field. If inner cut is not specified, the program will calculate.
Note: The area cut away is approximately equal for each baffle.
Triple Segmental Baffles
With Triple Segmental there are two styles of baffle:
1) A three-piece baffle with Intermediate Baffle Cuts Z. Expected Range =
2) A two-piece baffle with two different cuts:
An Outer Baffle Cut Y.
An Inner Baffle Cut X. (Similar to Double Segmental Baffle)
Input for Baffle Cut on Input | Exchanger Geometry | Geometry Summary | Baffle Cut (% D) is the outer Cut Y. Inner and Intermediate Cuts can be specified at Input | Exchanger Geometry | Baffles / Supports | Baffles under Baffle cut % - inner / outer / intermediate field. If is not specified, the program will calculate.
Note: The area cut away is approximately equal for each baffle.
For multi segmental baffles, It is recommended that the outer baffle cut is input (Y).
Keywords: Baffle Cut, Baffle Cut%, Double Segmental baffles, Inner Cut.
References: None |
Problem Statement: Aspen Properties can be used within Aspen EDR programs to generate physical properties of a pure component or mixture.
Since the V7.0 release (the latest release is V7.3), the components are now placed in one list that is used by both streams, which is different from previous releases, where separate component lists are generated for each stream.
The COMThermo and B-JAC component databank selection remains unchanged on a per stream basis. | Solution: Within versions newer than and including V7.0, a single stream component list is created. If the component does not exist in the stream, specify 0 in the composition field or leave blank and the program will ignore its presence when generating the physical properties.
Keywords: Aspen Properties, AP, component, list, composition
References: None |
Problem Statement: Thermosiphon outlet piping do not reflect gravitational losses | Solution: When the percent of head loss option is used for the outlet pipe no separate allowance is made for gravitational and accelerational pressure changes in this pipe. These are normally small, but they are all lumped together with the frictional change, when the percent head loss option is used.
When the From Pipework option is used, the program will calculate the gravitational changes for outlet piping.
When defining the inlet circuit, you can add up all lengths and specify as a general pipe length, but when defining the outlet circuit detailed input is required. You need to define the number of Elbows, Horizontal pipe length and diameter; Vertical pipe length and diameter as they are attached to the exchanger and column and then the program will calculate the pressure drop accurately.
Keywords: Gravitational pressure drop, thermosiphon, piping, thermosyphon
References: None |
Problem Statement: In Aspen EDR (Exchanger Design and Rating) programs, from the drop-down list of top menu option ? File, there are two options ? `Close? and `Exit?. What?s the difference between them? | Solution: Inside one EDR file, there could be more than one application for different types of heat exchangers. More details of how to have multiple applications within one EDR file can be found in TechicalSolution 132710.
`Close? applies to the individual application inside one EDR file. In other words, choosing this option will close the currently activated (most front) application window.
?Exit? option applies to the entire EDR program. In other words, choosing this option will close the current EDR program, including all the sub-applications inside this EDR file.
Keywords: Top menu, File, Close, Exit, applications, EDR file
References: None |
Problem Statement: Cost estimation is a very important concern for Aspen Tasc+ users. Here is a list of questions from our users and answers from HTFS+ development team. | Solution: Q1: How often do we update the material cost database?
A1: We typically update material cost with each major release, which is based on US nationwide average. They were last updated with Aspen HTFS+ V2006.5. We strongly recommend that customers maintain their own material costs for the materials they use most frequently. This can be done through Tools | Data Maintenance | Costing Database command on the user interface.
Q2: Do Aspen Tasc+ and Aspen ICARUS share the same data on material cost?
A2: Aspen Tasc+ does not use the same material prices as Aspen ICARUS. But we do communicate with the ICARUS development team to get material pricing trends.
Q3: What pricing data do fabricators use for their cost assessment?
A3: All fabricators maintain their own up-to-date pricing in Aspen Tasc+ through the Tools | Data Maintenance | Costing Database command mentioned above.
Keywords: cost estimation, heat exchanger cost, cost data
References: None |
Problem Statement: Sometimes it is necessary to model plugged tubes on a heat exchanger. How can this be done using Aspen Shell & Tube Exchanger? | Solution: On Shell & Tube Exchanger you can enter the number of Tubes which are plugged (blocked off) under Exchanger Geometry\Tubes\Number of tubes plugged.
The total number of tubes specified is used to determine the shell side layout, and flow areas for shell side flow.
The heat transfer area is then determined as a function of the difference between the total number of tubes and the number of plugged tubes. Usually the default for this item is zero, in which case there is not distinction between the actual number of tubes, and the number of thermally active tubes.
The plugged tubes are assumed to be uniformly distributed among the various passes in the heat exchanger. As from version 7.2, the number of tubes in each pass can be defined (SeeSolution 128398).
The plugged tubes will not be shown on the tubesheet layout. But the interaction with Aspen Shell&Tube Mechanical can be used to be able to display the plugged tubes on the diagram.
Keywords: Plugged tubes
References: None |
Problem Statement: How to remove warning message, 1215 for Kettle reboiler? | Solution: In a K shell, the shellside pressure drop is essentially due to the liquid level submerging the bundle that is controlled by the weir height. The recirculation model assumes the fluid entering the bundle is heated where it evaporates and reduces in density so reducing the gravitational pressure drop. This gravitational pressure drop is counteracted by the frictional pressure drop of the flowing fluid. At the top of the bundle, vapor will be taken off through the vapor nozzles and any excess liquid flows over the weir plate. However, some of the liquid at the surface of the K shell may re-circulated back down around the outside of the bundle and then pass through the bundle increasing the total flowrate through the bundle (compare with that entering the unit). This is the recirculation ratio reported in the Results | Thermal/Hydraulic Summary | Flow Analysis | Thermosyphon and Kettles tab. This recirculation flowrate is adjusted until the pressure drop in the bundle (friction and gravitational) matches that due to the height of liquid submerging the bundle.
Unless the pressure drops (gravitational and frictional matches), it is not possible to remove the warning 1215.
To remove this warning, you can modify the weir height under Input | Program Options | Thermal Analysis | Heat transfer tab or tube layout.
Keywords: Warning message, 1215, Kettle, shell, reboiler.
References: None |
Problem Statement: Why does the cost differ when the fluid allocation is changed in rating calculation mode for the same heat exchanger type and geometry? | Solution: Rationally, with the same type and size of heat exchanger, user may think the cost should stay the same regardless of fluid allocation when running in rating calculation mode. But user will notice the cost difference when the fluid side is changed. This difference is due to the pressure of the fluid at the shell and the tube sides. When the fluid side changes, the metal thickness changes because it is calculated according to the pressure of the process fluid. Thus cost difference is noticeable.
Keywords: Rating, cost difference, fluid allocation
References: None |
Problem Statement: In the TEMA Handbook 9th edition, section T-4.3.1 (page 7-5) says
The shell mean metal temperature, generally assumed to be equal to the shell fluid average temperature.
Sometimes this may be different from the value given by Aspen Shell & Tube in either the Results | Thermal / Hydraulic Summary | Heat transfer | MTD & Flux tab or the Results | Thermal / Hydraulic Summary | Performance | Shell by Shell Conditions tab
This | Solution: describes how the shell mean metal temperature is calculated.Solution
From Results | Calculation Details | Analysis along Shell | Interval Analysis tab, the shellside bulk fluid temperature is given with distance in the exchanger and from the Plots tab this can be seen graphically. Aspen Shell & Tube determines the mean shellside metal temperature from a length average. This can be different from the TEMA calculation if the shellside bulk temperature does not change linearly with distance.
Keywords: Mean Metal temperature, TEMA Handbook
References: None |
Problem Statement: Does Aspen Shell & Tube Exchanger (formerly Tasc+) report outlet component flow rates? | Solution: Starting from V7.0, Aspen Shell & Tube Exchanger (formerly Tasc+) reports component flow rates. The results are under Results || Thermal/Hydraulic Summary || Performance || Hot Stream Composition or Cold Stream Composition tab.
Note: You definitely need to specify inlet compositions to get outlet component flow rates.
Keywords: Outlet, composition
References: None |
Problem Statement: While trying to process the Collaborative Forecast (CF) overrides in a Demand Manager (DM) case I get an error message referencing the RCFTODM set. The error message could look like the following:
E0054: SCM Command Failed
SET: RCFTODM RULE: RREADSEC
COND: FMTDATA CFOVERSE FMTCFSET (SECURITY)
(Note: the import part of the error message is the referencing of set RCFTODM) | Solution: The rules in set RCFTODM call the FMTFDEF table (FMTDATA file definition). The FMTFDEF table contains the CF Integration section which defines the directory path for all files that are read from external file location related to CF data.
The file directories specified in FMTFDEF table (CF Integration section, line 29-55 (in the standard CAP case)) need to point to the correct file location. The sample pictured below is from the standard DM CAP case, your file locations may vary.
The last section of the COND statement i.e. (SECURITY) is the code for the directory that that contains the user_security.txt file.
Keywords: RCFTODM
FMTDATA file definition
References: None |
Problem Statement: 是否可用Aspen Shell & Tube Exchanger 程序来模拟虚拟防冲管？如果可以，如何定义相应设定？ | Solution: 是的，Aspen Shell & Tube Exchanger 程序可以模拟虚拟防冲管。
首先，你需要到Input > Exchanger Geometry > Nozzles > Shell/Tube Side Nozzles 界面去设定''Yes impingement''。
然后你要到Input > Exchanger Geometry > Nozzles > Impingement 界面去定义''Dummy tubes''。
然后用户就可以在界面下方开始输入相应的dummy tube的参数设定，比如管行数。
Keywords: Chinese-
References: None |
Problem Statement: How does one accurately generate the properties of an Electrolyte system in a Heat Exchanger in Aspen HTFS+? | Solution: If there is an electrolyte system in your heat exchanger, Aspen Properties ELECNRTL is the recommended physical property method. ELECNRTL uses special density models to accurately predict the density of aqueous electrolyte systems, but without running ELECWIZARD inside Aspen Properties, the property method will be simply reduced to NRTL. Following information provides a detailed information about generating the physical properties of an electrolyte system in a heat exchanger in a HTFS+ program.
1. Go to Start | Programs | Aspen Tech | Process Modeling | Aspen Properties and open an Aspen Properties user interface. Select 'Template' option and select 'Electrolytes with Metric or English units' and open the Aspen properties.
2. On the Aspen Properties user interface, go to Data | Set Up and select the valid phases to Vapor-Liquid
3. Then go to Data | Components and add all your components, note that water is already add to your system.
4. Then on same page, click the 'Elec Wizard' button to invoke electrolyte wizard.
5. On the electrolyte wizard, click Next and add all available components to 'Selected components' list and under options, uncheck the 'include salt formation' check box if you are not expecting any salt formation. Also HTFS+ engines can handle only vapor-liquid-liquid systems and cannot handle solid-vapor-liquid systems in the exchangers, so un-checking the salt formation option will avoid any physical property conflicts.
6. Then click Next, Next and before Finish, uncheck the 'use true components' and complete the electrolyte wizard set up.
7. Now go to Data | Properties and make sure the property method selected is ELECNRTL.
8. Then click the Next button to complete the properties set up.
9. Then run the Aspen Properties and make sure you get a status of result available.
10. Save this file as *.Aprbkp format.
Now open the Aspen Tasc+ or Aspen Acol+ (now called Aspen Shell & Tube Exchanger and Aspen Air Cooled Exchanger respectively) interface and go to the properties section and depending upon the allocation of this fluid, go to either hot or cold stream composition page and select the physical property package as Aspen Properties. Then go to Advanced Options Tab and select the radio button (option 2) to import an existing aspen property backup file and navigate to the saved Aspen properties file and import.
Now go back to composition tab and specify the composition of the components and leave the ionic components to empty. Go to properties page and click the generate properties to generate the properties.
Instead of creating the aspen properties backup file, you can achieve the same by opening the Aspen Tasc+ interface and go to the properties section and depending upon the allocation of this fluid go to either hot or cold stream composition page and select the physical property package as Aspen Properties. Add all your components and specify the property method as ELECNRTL and then go to Advanced Options Tab and leave it to default check option 1. Click on Aspen Properties browser and Run the Electrolyte Wizard as mentioned above and save the file. Go to properties page and click the generate properties to generate the properties.
Keywords: Aspen Properties, Electrolyte, ELECNRTL, Properties.
References: None |
Problem Statement: In Aspen Shell & Tube Exchanger, it is possible to set different baffle types, like single, double and triple segmental baffles for example from Input | Exchanger Geometry | Geometry Summary or Input | Exchanger Geometry | Baffle/Supports | Baffle tab. The selection of the baffle type will have an impact on the flow velocities on the shellside and hence the heat transfer and pressure drop.
Being able to specify triple segmental baffles is relatively new, where this | Solution: describes the geometry of the arrangement, which is different to that described in the ?Standards of the Tubular Exchanger Manufacturers Association? TEMA Handbook, 9th Edition page 5.4-1.Solution
The baffle arrangement for triple segmental baffles is as shown below, where there are two forms of baffles;
1. A three-piece baffle with intermediate baffle cuts Z
2. A two-piece baffle with two different cuts;
a. An outer baffle cut Y
b. An inner baffle cut X (NOTE: this is measured from the exchanger centreline)
It is recommended that the outer baffle cut is input (Y) and that the area cut away should be approximately equal for each baffle.
Keywords: None
References: None |
Problem Statement: After running an EDR thermal case, in the Results | Calculation Details section, the program reports stream properties in terms of one vapour phase and one liquid phase separately. The liquid properties output in the results are for the overall liquid phase
When having two liquid phases present in a stream (users can check it on the Input | Property Data | Hot/Cold Stream Properties | Properties tab), how does the program calculate the overall liquid phases properties? | Solution: The basic methods of calculating different types of property parameters for combining the two liquid phases are described below.
Density: calculate a mass fraction average of the two liquid phase densities
Specific Heat: calculate a mass average specific heat in the same way as for the density
Thermal conductivity: calculate a local volume-averaged value of the two thermal conductivities.
Surface Tension: calculate a local volume-averaged value of the two surface tensions.
Effective Viscosity: Based on ''Brinkman'' method.
The calculations of two liquid phase (immiscible mixture) properties are available from 2006 and all the later releases of Aspen EDR products.
Some recommended methods when using the Aspen Properties databank for different systems are:
Chemical: NTRL-v, UNIQUAC-v, UNIFAC-LL
Oil & Gas: PR, SRK, LK-PLOCK, NRTL
When using COMThermo:
PR, SRK, LK-PLOCK, NRTL, UNIFAC-LLE
Users can now use VLL (Vapour-Liquid-Liquid) methods for greater accuracy, not VL (Vapour-Liquid) approximations, when two liquid phases are present.
Details of the above property methods can be found in ''AspenPhysPropModelsV7_1-Ref.pdf'' in the ''Documentation'' folder. This is normally found in the ''C:\Program Files\AspenTech\Documentation\Aspen Engineering V7_1\Aspen Properties'' directory.
Keywords: Two liquid phases, Immiscible mixture, Property Data, Mass fraction average, Density, Specific Heat, Volume fraction average, Thermal conductivity, Surface Tension, Brinkman method, Effective Viscosity
References: None |
Problem Statement: How do I extract column reboiler data from Aspen HYSYS in Aspen Shell & Tube Exchanger? | Solution: Aspen Shell & Tube Exchanger cannot detect column reboiler when trying to import from the Hysys file.A In order to import reboiler stream data from Hysys file, there are few steps you have to do in the Hysys file.
First, you have to export the internal stream out from the column environment to the main environment and add a heat exchanger to model the reboiler.
Here are the steps to export the column internal stream:
1. Under Flowsheet tab, go to a??Internal Streamsa?? page. Type a new name, example a??To Reboiler 2a??. This is the stream going into the reboiler and this stream is coming out of the last stage of the column, for example stage 10 and it is liquid phase. Check Export after defining the stage number and phase as shown in screenshot below. You will see there is a stream created in the main environment with the stream properties and conditions exactly the same as the internal stream. Make sure you run the column to converge it.
2. After exporting the internal stream, add a heat exchanger in the main environment to model the reboiler. Add a separator and define the liquid outlet stream from the column bottom outlet stream. You can use a balance block to set the composition and 2 set blocks to fix the pressure and temperature. Example file is attached for reference.
3. Once the Hysys file is ready, you can import the heat exchanger data into Aspen Shell & Tube Exchanger. This heat exchanger represents the reboiler in the column.
Keywords: Column reboiler, import data, HYSYS
References: None |
Problem Statement: 在选择'User specified properties'的情况下, 用户要自己手动输入物流的物性参数. 有些时候用户可能没有在某特定温度变化范围内的焓值或者焓变, 所有此情况下的热焓曲线无法生成. 本解决方案讨论的是在此种情况下, 如何通过物流本身的物性参数来计算出焓值的变化. | Solution: 在解决方案119148里, 焓变的计算公式如下:
dh = Latent Heat * dx + [(1-x) * Cpl + x * Cpg] * dT
其中:
dh = dT范围内的焓值变化
dT =一个极小的温度变化
dx = dT范围内的气化率变化
x =此温度范围内的平均气化率
Cpl, Cpg =此温度范围内物流的平均液相比热容和平均气相比热容
Latent Heat =潜热
热力学计算里, 特定温度区间内的焓值的变化很重要. 一旦焓变能够确定, 每个温度点的特定焓值就能确定. 如果设定初始温度点的特定焓值为零, 则接下来所有后续温度点下的特定焓值就能被确定.
通过总结,有以下四种计算焓变的方法:
对气液混合相来说, dh = Latent Heat * dx + [(1-x) * Cpl + x * Cpg] * dT, 这里 '[(1-x) * Cpl + x * Cpg] * dT' 项是混合相在露点和泡点之间进行相变时的显热.
? 对纯组分物流来的相变过程来说, dh = Latent Heat * dx. 这是因为纯组分的露点和泡点是同一温度点, 所以显热为零.
? 对单一相物流来说, 对单液相dh = Cpl * dT, 对单气相dh = Cgl * dT. 这是因为在没有相变的情况下, 没有潜热存在. 气相的比热容在不同压力下可能很不同. 用户在定义不同压力下气相的物性参数时要小心, 比如, 在几个压力下的第一初始温度点应该是相同的,在此温度点下的特定焓值应该是相同的(比如说设为零).
? 不管有无相变或者是否是纯组分,传热计算里最基本的焓变计算公式应该是dh = Q/m, Q是传热过程的总热载, m是物流的质量流量.
Keywords: 焓变, 特定焓值, 热载, 热功率, 热焓曲线, 用户定义物性参数, CN-
References: None |
Problem Statement: When using the Aspen Shell & Tube Design and Rating utility inside Aspen HYSYS, the user can input the values through the Process menu.
However after running the utility, these numbers are not the same: | Solution: The reason for this is that the fouling factor output is based in the outer diameter, while the input is based on Inner Diameter.
If the user wants to have a consistency between these values, a correction factor must be used.
Keywords: Fouling factor, Heat exchanger, Utility
References: None |
Problem Statement: Under what conditions are the evaporators considered operating with 'continuous falling film'? | Solution: The criteria for a continuous film in falling film evaporators is that the film flowrate is above the minimum wetting rate.
The minimum wetting rate is the film flowrate below which the tube walls are not fully wetted, causing the thermal performance of the evaporator to deteriorate. Aspen Shell & Tube Exchanger currently uses Mikielewicz and Moszynski (1976) method.
The implementation of the minimum wetting rate check depends on the calculation mode. In DESIGN mode, a maximum tube count is calculated above which the liquid flowrate at the bottom of the tubes would fall below the minimum. In CHECKING or SIMULATION mode, a warning is issued if the liquid flowrate at the bottom of the tubes is below the minimum wetting rate. The warning will appear in Results | Results Summary | Warnings & Messages.
In addition, the annular flow regime of the falling film evaporator is subjected to entrainment of liquid droplets into the gas core. Aspen Shell & Tube Exchanger calculates the heat transfer and pressure drop and performs its minimum wetting rate check assuming that all the liquid is in film flow. It then calculates the entrained mass flow at outlet and issues a warning if it exceeds 10% of the outlet liquid flowrate. The entrained mass flow predicted can only be treated as a general guide, since the accuracy of its method is poor and that the resulting value should only be regarded as an order of magnitude estimate
Keywords: falling film, evaporator
References: Mikielewicz, J and Moszynski, J.R. (1976) Minimum thickness of liquid film flowing vertically down a solid surface, Int. J. Heat Mass Transfer, Vol. 19, pp 771-776. |
Problem Statement: How does Aspen Shell & Tube Exchanger program calculate the span length for Tube location 2 (tube row just outside the baffle overlap) for reporting in the Vibration & Resonance analysis? | Solution: Tube Row 2 is one of the representative tubes considered for the vibration analysis. Tube row 2 is the row just outside baffle overlap. Based on the experience that there are certain tube rows within an exchanger that are most likely to suffer vibration damage, Aspen Shell & Tube program follows a conservative approach for the selection of tube rows. The program looks for the longest unsupported span length tube (at inlet or outlet) which consequently gives the lowest tube natural frequency.
See the figure 1 below which shows Tube location 1 (Top tube row), Tube location 2 (row outside baffle overlap), Tube Location 4( Row in Baffle overlap), and Tube location 5 (Bottom tube row). This case shows we have two potential tube 2 locations, which we will call 2a and 2b just for the purpose of distinction. In this case, because the Spacing at the outlet region, Tube 2a, is greater than the spacing at the inlet region, Tube 2b, the longest unsupported length for Tube row 2a is used for the vibration and resonance analysis.
Figure 2 below shows the same case as above but with an extra baffle which has resulted in lower Spacing at outlet which means the unsupported span length for Tube location 2a has been reduced. Now Aspen Shell & Tube program compares the Tube row 2a and Tube row 2b to see which one of them has the longest unsupported span length. So, in this case, Tube row 2b becomes Tube row 2 for the vibration and resonance analysis.
After a successful run of the program, you can see the span lengths for various tube locations in Results | Results Summary | Thermal / Hydraulic Summary | Vibration & Resonance Analysis | Resonance Analysis (HTFS) tab.
Keywords:
References: None |
Problem Statement: What does Operation Warning 1324 mean, and how do I prevent it? | Solution: This item applies to horizontal shell side condensers and is applicable when there is a lute, side nozzle or some other device or geometric feature that causes some of the tubes in the exchanger to be submerged under the condensate.
The program calculates the velocity and hence the heat transfer coefficient for condensate cooling based on the fraction of heat transfer surface area in the tubes that is submerged by the condensate. The vapor velocity used in the gas-phase heat transfer coefficient is also adjusted to take account of the reduced vapor flow area.
The program compares the input value for the surface area with the calculated fraction of the surface that needs to be submerged to meet the condensate cooling duty.
The input value can be adjusted in successive runs until the input and calculated submergence are in agreement.
Whenever you get this warning, go to Input | Program Options | Thermal analysis | Heat Transfer and input the fractional value for fraction of tube area submerged for shell side condensers. The fraction submerged can be increased until the warning is no longer exists.
Keywords: Operation warning
Condenser
Required fraction of surface area
References: None |
Problem Statement: How do I select a specific tube for vibration check? | Solution: The risk of vibration in any tube in an exchanger depends on where it is supported, by baffles or other supports, and on local flow velocities along its length. Aspen Shell & Tube Exchanger automatically selects a small representative set of tubes to perform vibration checks in older versions.
In Aspen Shell & Tube Exchanger V7.3.2 we have introduced some additional facilities including:
An extended set of program-selected representative tubes are checked
An option to select any other tube in the exchanger for vibration checking (up to six such tubes at a time)
Display of vibration-check tubes on the Tube Layout, both program-selected and user-selected tubes
Enhanced tabular output of tube vibration and resonance results
To select another tube for vibration checks, navigate to Geometry Summary | Geometry and specify Use Existing under Tube Layout. On the Tube Layout tab, right-click a tube to select it. Select Vibration on the context menu, and then Mark.
After you run the program, you will see your additional tube(s) in the Vibration and Resonance Analysis results and on the Tube Layout.
Keywords: tube layout, customize, vibration, select
References: None |
Problem Statement: What do the different damping values under the Fluid Elastic Instability Analysis mean? | Solution: The software initially considers three general levels of damping defined by log decrements of 0.1, 0.03 and 0.01. The highest value, 0.1, reflects heavy damping, the value of 0.03 serves as a medium value, while 0.01 would represent light damping. Typical log decrements for a single phase liquid stream on the shell side tend to be close to 0.1 (heavy). For gases, typical values are closer to 0.03. Two-phase fluid damping is more difficult to analyze, but may be assumed to lie between these ranges..
The software calculates a typical damping level in the 'Estimated' table of the Tables of Fluid-Elastic Instability Assessment based on the careful and extensive comparisons of numerous research studies. This estimated damping value may apply to the majority of tubes within the heat exchanger.
The Estimated fluid elastic instability assessment table indicates whether there is a low, medium or a heavy damping or vibration at a particular place in the exchanger and gives a user an idea where he/she is at.
There are a few questions that may come up regarding this topic. For example, if there is an indication that vibration is only predicted at a log decrement of 0.01 on Damping table where as the estimated log decrement on the table is 0.61, then this should be OK. However, the estimated log decrement is based on a perfect bundle (all holes same size and in alignment, tube walls all the same thickness etc) so it is still up to the user to look at it sensibly and not just believe the numbers because there is no perfect bundle. It all depends on the implications of failure. For example, with nuclear or offshore the implications are severe so you would want to remove all possibility of vibration, whereas with a small oil heater you may be prepared to take a risk.
Some other question related to this issue might come up if there is an asterisk on the Damping table where damping is 0.01, 0.03 and 0.1 and there is NO asterisk on the Estimated table on the right side where damping or log Dec is calculated. Should we take in action in this case? It is up to the user's engineering judgment and it depends on the particular system system. However in this case, the recommendation is to remove all asterisks from both tables Damping and Estimated to remove all vibration risks.
Keywords: FEI, Damping, Fluid Elastic Instability
References: None |
Problem Statement: A Process Simulator File (PSF) can be used to transfer data to the Exchanger Design and Rating (EDR) suite of programs, where the file can contain both process and physical property data. This | Solution: describes two methods to generate a PSF file using HYSYS.
Solution
The two methods are detailed below;
Method 1:
From within the standalone EDR program, from the main menu, select File | Import from | Aspen HYSYS V7.x.
A popup box will appear where a HYSYS case can be selected. The HYSYS file will then be opened and searched for heat exchangers, LNG blocks and heaters/coolers.
A popup box will appear as below, where the heat exchanger of interest must be highlighted. If required, additional pressure levels can be added. Click on OK.
Click on the 'Save HYSYS Generated PSF File' from the box below.
Enter file name and location for the file.
Method 2:
Members of the HTFS Research Network http://www.aspentech.com/htfs/resnet.asp can navigate to the Aspen HTFS Tools section and download the PSF File Generator Utility.
This utility allows a HYSYS case to be read and will identify any heat exchangers in the simulation. There are 2 types of heat exchangers - shell and tube and LNG (compact/plate fin). You will be able to select the exchanger and then generate a PSF file which contains the process and property data for the chosen exchanger.
Note: You must have a working version of HYSYS already installed on your computer for this utility to work.
Keywords:
References: None |
Problem Statement: After running the file, I get Input Warning 1243. What does it mean? | Solution: The bundle band orientation corresponds to the Pass layout that has been chosen under Input | Geometry Summary | Bundle Layout (i.e. Mixed, Quadrant and Ribbon).
The pass partition lane refers to the gaps between the tubes. For example, in this case, there are three passes.
The steam will be flowing in Horizontal direction. And with this arrangement, the steam will flow will go mainly through the pass partition lanes, thus not having a lot of vertical flowpaths to be in contact with the tubes. This is what the message is referring as “significant by-passing”.
The recommendation of changing the bundle orientation will give the “H” a turn. So in this case, what will happen is that while the steam will still flow horizontally, the spaces between the passes will contribute to a better distribution of the steam flow to be in contact with the tubes.
Other alternative is to choose a different arrangement. In this case, a quadrant arrangement will also help to reduce this type of messages as the number of horizontal passes will be reduced to one.
The baffle cut plays here also a role. The effect on the flow stream (in this case, the steam), will depend on the baffle orientation. It is desired to minimize the number of bypass lanes perpendicular to the baffle cut to improve the flow distribution and prevent by-pass regions. So this is why in this case we want to minimize the number of horizontal pass partition lanes and choose a different arrangement.
Keywords: Pass partition lane, input warning, exchanger, tubes, arrangement, quadrant, tube layout, pass layout, flow,
References: None |
Problem Statement: The Exchanger Design and Rating (EDR) program can be linked to Aspen Plus for the detailed calculation of Shell and Tube Exchangers.
Normally from a HeatX block in Aspen Plus, the Aspen Shell & Tube Exchanger can be selected from the Setup | Specification tab. Once this is selected the location for the hot fluid can be set and the Type of calculation, Design, Rating and Simulation set. From EDR Options | Input File tab, the location of the EDR datafile is then set.
When the Aspen Plus simulation is run, then detail calculations are performed with the Shell &Tube program and results can be seen within the EDR Browser. However, in the Control Panel, you may see the error ?unable to load dynamic library ZETASC?. This | Solution: describes how to set Aspen Plus and Shell & Tube, so that the programs can run together, providing both Aspen Plus and EDR are installed on the computer.Solution
1. From Start | Run enter Regedit and OK
2a. Assuming you have a 32 bit operating system, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\AspenTech\Aspen Plus\24.0\Compatibility\Aspen Exchanger Design and Rating. Go to Step 3.
2b. For Windows 64 bit operating systems, the path is slightly different at
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\AspenTech\Aspen Plus\24.0\Compatibility\Aspen Exchanger Design and Rating. Go to Step 3.
3. Under here you should see 3 keys, default, 1 and CurVer.
4. It is likely that key 1 is missing? If so follow the following steps;
a. Under the keys, right mouse click and select New, String Value
b. Right mouse click on the New key and rename to 1
c. Modify key 1 and set the Value data to 24.0
5. Close Regedit
Now start Aspen Plus where EDR should now perform calculations when run.
Alternatively, download the appropriate attached registry file and double click to install the registry settings.
Keywords: Windows 32bit, 64bit
References: None |
Problem Statement: Stream data views in the simulation flowsheet view are not persisted when a user logs off the client. The next time user logs in, and displays the same model's flowsheet, the stream data tables are not displayed, and each stream has a leader line but no table. | Solution: The problem has been resolved. This is a client side issue, the Aspen Plus or HYSYS computer needs to be updated. To update the Aspen Plus or HYSYS computer,you can either apply the latest Aspen Plus or HYSYS patch or download and apply the Aspen Search client install from the following location.
Keywords:
References: None |
Problem Statement: You are trying to expand your Collaborative Demand Manager (CDM) environment to contain 24 months of forecast instead of 18 months.
Changes were made to CDM Publishing in the development environment of the Aspen Collaborative Forecasting (CF) system. However, after moving the changes into production, the option menu for Time Periods did not recognize that 24 months were available -- it still went out to 18. This problem also occurred in View Data and Create Overrides as well as in the End Date and Begin Date.
The View Time Fence did go out to 24 months and setting the default time periods allowed settings out to 23 months. But anything over 17 caused the End Date to default to the first period. Data for the additional periods displayed in Toad. Everything that worked before the changes were made still worked. | Solution: The production server's CF service need to be restarted. Restarting the CF WebLogic service resolves the issue.
In production, it is recommended that you restart the CF services at least once per month for every roll forward. In this case, adding a number of time periods requires a refresh which is accomplished by restarting the CF services. WebLogic services are embedded in the CF services.
TO RESTART THE SERVICES
? From the desktop, right click on My Computer or Server Name.
Click on Manage
Select Computer Management
Double click on Services and Applications
Double click on Services to display a list of the services
Scroll to beasvc myDomain_myAdminServer (may be named differently) and check the status.
Restart the Service. Right click on the service name to change the status.
If the service is Started, select Stop and then Start.
If the service is Stopped, select Start.
Keywords: weblogic, restarting services, date range
References: None |
Problem Statement: How do I create a component that is not available in any of the physical property packages databank? | Solution: To create a component that is not in the database, you will have to create a private user databank and that is on Tools --> Data Maintenance --> Chemical Database --> Chemical Databank Maintenance screen.
On the lower left hand corner of the screen, press the 'Add' button then type the new component name on the screen that pops up then click 'Ok' to close that screen. The new component will show in the list on Chemical Databank Maintenance screen. Specify its constant and temperature dependant properties using the two tabs on the left hand side of the screen. Once this component is added with its properties to the private user databank.
The component can then be accessed from the Hot or Cold Side Composition tab. Select B-JAC Databank as the Physical property package and click ont he Search Databank button. In the Search Chemical Component screen, change the Databank to User from the drop down list.
Keywords: Data Bank
data bank
References: None |
Problem Statement: What is happening when I select the Renew Working Forecast icon in AspenTech Demand Manager? What part of the forecast is being renewed? | Solution: The Renew Working Forecast icon from the Create Statistical Forecast screen (Forecast Generation>Create Statistical Forecast), calls the rule specified in APPDATA (FCRNWINIT). In the standard Demand Manager CAP case, FCRNWINIT is set to the rule RRENEW1I. In the standard CAP case the working forecast is retained for all past months and the rule only renews the current and future months with lot size, overrides and events.
To determine what Renew Working Forecast is doing your system, open the rule stated in APPDATA (FCRNWINIT) and trace the rule to determine what is happening in your system. Please feel free to contact Aspen Support for help decoding the rule.
Keywords: Working Forecast
Forecast
References: None |
Problem Statement: In some cases, when trying to run an EDR case that has imported process and property data from a Aspen HYSYS case, a fatal error is given due to a heat load imbalance, which is generally caused by interpolation / extrapolation of the property data. This | Solution: addresses how to prevent such errors.Solution
The problems are due to the inconsistencies between the outlet pressures in the EDR case and the default 2nd pressures during the importing procedures. The 2nd pressures need to be manually re-set during importing. For more details please refer to the attached Word document.
Please be aware that this problem only occurs with version 2006.5 and older, while it has been resolved in Version 7.0 onwards.
Keywords: HYSYS, HTFS+, EDR, Shell & Tube Exchanger, Air Cooled Exchanger, Tasc+, Acol+, Import, Property data transfer, default 2nd pressure level, Fatal error, Heat load imbalance, Duty imbalance
References: None |
Problem Statement: The viscosity of a mixture stream reported by EDR might not match literature of experimental values when the components are defined individually. | Solution: Aspen Exchanger Design and Rating contains some pre-defined mixtures within the program database where the properties have been fit to match literature values. This is the case of, for example, Ethanol 50%.
However sometimes the user might be using a different mixture that is not present in the database. So individual components need to be defined.
For streams with individual components, standard mixture rules are applied. In this case it is recommended to use Aspen Properties. However, Aspen Properties calculates pure component viscosities and uses standard mixing rules to calculate the mixture viscosity. The accuracy of the resulting mixture viscosity is unknown and experimental mixture viscosity values must be curve-fit to give a good match, even in Aspen Properties.
One recommended alternative would be to generate properties at the temperatures where viscosities are known, and then manually enter the known viscosities.
Keywords: Viscosity
Mixture
Heat exchanger
References: None |
Problem Statement: Is it possible to use relative humidity to specify composition in Aspen Tasc+? | Solution: No, relative humidity cannot be used as a compositional basis in Aspen Tasc+; only overall composition (on a mass or molar basis) is allowed when defining stream composition.
Keywords: Tasc+, humidity, composition, specification
References: None |
Problem Statement: In Aspen Exchanger Design & Rating (EDR), user can select horizontal cut Single segmental baffle with F type shell. However, you will notice that the Setting plan shows a Double segmental baffle which has three baffle pieces for this case. | Solution: A horizontal-cut single segmental baffle in an F-shell is equivalent to a double segmental baffle, which has three baffle pieces. You can see that, with F type shell, you have the options to type in Inner cut & Outer cut for Single segmental baffle under Input | Exchanger Geometry | Baffles/Supports | Baffles tab. Below is the screenshot of how a horizontal cut single baffle in a F shell will look like in the Setting plan-
Under Results | Mechanical Summary | Setting plan & Tubesheet Layout tab, If you select the single piece baffle, which has two outer cuts, one at the top and one at the bottom as shown below in the snapshot. You can see the percentage top & bottom cut are the same that user has specified for Outer cut under Input | Exchanger Geometry | Baffles/Supports | Baffles tab.
If you select a piece of the two-piece baffle, you will see the (inner) cut as measured from the centre line. For example the top baffle piece has a lower cut of 11.5% measured from the centre line. This matches up with the inner cut as given in the exchanger geometry input. The pieces of the two-piece baffle of course only really have one cut which is what the user specifies and the second cut is the remaining 50% measure from the center line.
Keywords:
References: None |
Problem Statement: How do I use the new input Specify Some Sizes in Design? | Solution: Specify Some Sizes in Design is a special input which is only available in the console, and is only used in design mode. When a??Yesa?? is selected, some of the Exchanger Size inputs, normally grayed-out in design mode, become available. If any of these inputs is selected, it is used to set the (default) values of the corresponding minimum and maximum parameters (normally found in Design Options | Geometry Limits) to the specified value.
Note that since the size parameter is used to set only the default design limit, if the Design Limit parameter has been explicitly input specifying the corresponding size parameter on the console will have no effect.
If you have a design case which has previously been run in Simulation Mode, then it is possible that all of the size parameters are already set. When you switch a??Specify Some Sizes in Designa?? to Yes, these parameters will become available, and you delete any values which you want the Design process to determine.
Keywords: new in V8.0, console, interface, size, input
References: None |
Problem Statement: In Tasc+, Latent Heat is shown on the TEMA sheet as a physical property, and also on the Results | Thermal/Hydraulic Summary | Heat Transfer | Duty Distribution page.
How are the two Latent Heat parameters related to each other? | Solution: The two places where Latent Heat is explicitly referred are shown below.
1) Tasc+ Screen Shot: TEMA Sheet
For later discussion, we denote Latent Heat on screen 1) as LH_e/m. We also denote the materials transferred between vapor and liquid phase as M_lv. From the above screen,
LH_e/m = 1018 Btu/lb
M_lv = 22046 lb/h
LH_e/m is a point property of the materials at inlet or outlet. It has a dimension of energy/mass. It specifies the energy required to move unit amount of materials between vapor and liquid.
2) Tasc+ Screen Shot: Results | Thermal/Hydraulic Summary | Heat Transfer | Duty Distribution
For later discussion, we denote Latent Heat on screen 2) as LH_e/t. The quantity LH_e/t is the portion of the total duty in the heat exchanger attributed to moving materials from one phase to another. It has a dimension of energy/time. In the above screen,
LH_e/t = 22443130 Btu/h
For the simplest cases where the latent heat LH_e/m remains constant over the entire flow path, the two quantities, LH_e/m and LH_e/t, are related as following,
LH_e/t = LH_e/m * M_lv
Using this relation to current example, we get
LH_e/t = 22443130 Btu/h
LH_e/m * M_lv = 22443838 Btu/h
Within Tasc+, the right hand side is calculated as a sum over zones along the flow path. Therefore, it is important to provided adequate data points between the inlet and outlet temperature range to assure accurate results.
Keywords: Latent heat, shell and tube, exchanger
References: None |
Problem Statement: What are the new enhancements done to the On-Line Help for EDR V7.0? | Solution: The on-line help that supports the EDR programs has been restructured for the V7.0 release. This involves dividing the help text for each application into logical chapters that reflect the structure used within each application.
For example:
Aspen Shell & Tube Exchanger (Shell&Tube)
1. Shell & Tube Input - Information about all of the inputs
2. Shell &Tube Results - Information about each results screen
3. Shell & Tube Getting Started Guide - A tutorial to take you through a thermal design
4. Shell & Tube Heat Exchangers - General background information
Within each application, Overview sections have been added containing hyperlinks to other sections of the help that will aid the navigation of the help file.
More use has been made of the Appendix section of the EDR Help file, which now includes the Physical Property Data and a new Shell and Tube Geometry appendix that will contain generic information applicable to the geometry of shell and tube heat exchangers.
Keywords: enhancement, help, V7, EDR
References: None |
Problem Statement: Why is the value of the Shell ID in the performance page different from the value in the geometry summary and TEMA sheet? | Solution: The shell diameter reported in the Performance Page is a rounded value. This can be slightly different from that reported in the Geometry Summary and the TEMA sheet if a different dimensional standard is set in the Application Option page. Internally, the software rounded the inch to mm and when the rounded data is converted back to mm then the value can differ from the input value as given in the Geometry Summary. This data truncation can be eliminated by setting the same dimensional standard as used for the model setup. The following screenshot shows where the dimensional standard is specified.
Keywords: Shell Diameter, TEMA Sheet, Dimensional Standard
References: None |
Problem Statement: I am running a case and getting Input Warning 1062 regarding the location of the hot fluid. What does it mean? | Solution: Input Warning 1062 is indicating a more fouling or hazardous fluid is on the shell side and suggesting you to change it to tube side to avoid any corrosion and erosion on the shell side and for easy cleaning and handling of exchanger.
This is just a recommendation by the program and must be evaluated used your own judgement and knowledge on process fluids and heat exchanger design.
If for example, the same fluid is on both sides, this warning can easily be ignored
Keywords: Fluid allocation
Hot fluid
Shellside
References: None |
Problem Statement: Fluid elastic instability (FEI) is important for both gases and liquids. It occurs whenever a fluid flows through an exchanger and some motion is imparted to the tubes. The displacement of a tube from its normal position alters the flow field through the tube bundle which in turn alters the force balance on other tubes. The fluid imparts energy to the tubes, where the energy is dissipated by the damping of the tube. As the velocity of the fluid is increased the amount of energy imparted to the tubes increases. If the energy imparted to the tubes exceeds that dissipated by damping a vibration of increasing amplitude is set up. A critical flow velocity can be identified below which no vibration problems are envisaged and above which significant damage may occur. | Solution: This is not a resonance but a true instability with the amplitude of vibration limited only by colliding with other tubes, baffles or the shell.
In Aspen Shell & Tube Exchanger (Tasc+), Fluid Elastic Instability warning messages are generated if the ratio of W/Wc >1, where W is actual flowrate and Wc is the critical flowrate for onset of fluid elastic instability. These ratios are shown in Vibration & Resonance Analysis section.
Some general attempts to avoid FEI:
Decrease fluid velocity
Increase the tube natural frequency by decreasing the span lengths (for example by introducing intermediate support plates between baffles) or by increasing the tube diameter. Note that increasing the tube wall thickness has almost no effect.
Increase damping by reducing the clearances between tube and baffle
Increase the tube pitch
Remove the tubes in the window region which have double length spans
Keywords: Fluid Elastic Instability, Acoustic Frequency, Avoid Vibration
References: None |
Problem Statement: The enthalpy values shown in Aspen Tasc+ / Aspen Shell & Tube Exchanger (and Aspen Acol+ / Aspen Air Cooled Exchanger) appear different from the data imported from Aspen HYSYS. | Solution: The absolute value of the stream enthalpies may be different due to the chosen reference state, however it is the change in enthalpy that is important. The enthalpy difference between two states (for example, the difference between the outlet and inlet streams in an exchanger) in Aspen HYSYS and the corresponding difference in the HTFS+ program must be same.
Keywords: HYSYS, import, export, specific, enthalpy, mass
References: None |
Problem Statement: Where do I specify the de-resonating baffles in Aspen Shell & Tube Exchanger? | Solution: Starting with Aspen Shell & Tube Exchanger V 7.0 you can now explicitly specify the number and location of de-resonating baffles, which can protect against any acoustic resonance, one of the conditions reported in the vibration output. These baffles do not appear on the tube layout output, but are handled fully in the internal calculations. If
tubes need to be removed to make space for these baffles, you can simply specify the remaining number of tubes in the input.
To specify the de-resonating baffles, navigate to the Deresonating Baffles tab on the Input | Exchanger Geometry | Baffles/Supports page and specify the locations.
Keywords: de-resonating baffles, support, vibration, acoustic resonance
References: None |
Problem Statement: How can I set cumulative load in Tasc+? | Solution: Tasc+ doesn?t have a cumulative load input, however, the specific enthalpy is equivalent.
Specific enthalpy can be calculated as in the example below:
Heat load [BTU/h] = Flow rate [lb/h] x Specific Enthalpy [BTU/lb]
Keywords: cumulative, load, heat, specific, enthalpy
References: None |
Problem Statement: How do I generate custom export templates? | Solution: Aspen Shell & Tube Exchanger provides three templates for each product, i.e. Blank, TEMA and Full results.
1. Select template from folder where the program is installed such as Program Files-> AspenTech-> Aspen Exchanger Design and Rating Vx.xx-> Excel Templates-> Shell&TubeTEMAsheet.xltm.
2. Export results in Aspen Shell & Tube Exchanger to Excel using File-> Export to-> Excel Specified template.
The results from Aspen Shell & Tube Exchanger can now be formatted in Excel for reporting purposes.
Keywords: Export data, EDR, custom templates, Excel
References: None |
Problem Statement: In a ''multiple shells in series'' case, sometime users may see a discrepancy in terms of overall pressure drop for both shell and tube side, between the output of Aspen Shell & Tube Exchanger and their own calculation. What is the cause of this discrepancy? | Solution: The cause of the Pressure Drop discrepancy may be due to the Intermediate Nozzles that are used to connect multiple exchangers in series, and Shell & Tube Exchanger considers their presence as compulsory.
On Results | Thermal / Hydraulic Summary | Pressure Drop tab, users should see the intermediate nozzles being taken into account in terms of both shellside and tubeside pressure drop analysis. This may have given fairly different overall pressure drop values from the users' own evaluation, especially when the pressure drops through these intermediate nozzles are considerable percentage of the total pressure drop.
If this is the case, users shall bear in mind with these intermediate nozzle pressure drop values, when comparing the program reported values with their own pressure drop evaluation.
Keywords: Pressure drop discrepancy, Multiple exchangers in series, Multiple shells in series, Intermediate nozzles.
References: None |
Problem Statement: How do I resolve error in loading DLL when importing physical property data from Aspen HYSYS? | Solution: When importing physical property and process data from Aspen HYSYS into an Aspen EDR, EDR will search the Windows registry for the path of hysys.exe and the type library hysys.tlb. If any of the files is missing under the installation directory, you will get this message.
In Aspen HYSYS V7.2, the files are typically under C:\Program Files\AspenTech\Aspen HYSYS V7.2\, or C:\Program Files (x86)\AspenTech\Aspen HYSYS V7.2\ (for 64 bit OS).
Keywords: error in loading DLL
References: None |
Problem Statement: Natural frequency is an inherent characteristic of a body and is a primary parameter in vibration analysis. A heat exchanger tube in principle has an infinite set of vibration frequencies, but only the lowest natural frequency is usually important, and this is all that Shell & Tube Exchanger (Tasc+) considers.
A tube in a heat exchanger can be considered as a spring and mass system with damping, which is subject to an oscillatory force by the presence of the flow. The amplitude of vibration will reach a maximum when the forcing frequency is close to the natural frequency of vibration of the system and is dependent upon the available damping.
In practice if the natural frequency and the forcing frequency mechanisms are similar, then excess vibration is assumed during the design despite the presence of damping. If such coincidences in the frequency occur then steps should be taken to change the natural frequency of the tube to avoid the problem.
Described below is an equation that can be used to determine the natural frequency of a straight length of tubes and changes that can be made to remove the natural frequency away from the exciting frequency to avoid lock -in effect. | Solution: A basic equation that may be used to determine the natural frequency of a straight tube is:
Where:
f - Tube natural frequency (in Hertz)
l - Tube span length (distance between supports)
E - Tube material property (Youngs modulus)
I - Tube section (second moment of area)
m- Effective mass (internal fluid, tube material plus surrounding fluid)
Beta - A factor based on the nature of the tube support system, i.e.
Number of baffles
Span ratios (ratio of endspan length different to mid-span length)
Type of span support (clamped at tubesheet, pin joints at baffles)
Axial stress
Important notes:
1. The most efficient way of increasing the tube natural frequency is to decrease the span length.
2. Increasing the tube diameter increases the tube natural frequency (i.e. second moment of area).
3. Note that increasing the tube wall thickness has almost no effect.
4. The natural frequency of a single tube is generally governed by the lowest natural frequency of its individual spans (i.e. the longest span).
5. Special consideration is given to the calculation of U-Tube Bundles natural frequencies.
Keywords: Natural Frequency, Increase, Vibration
References: None |
Problem Statement: In Design Mode, the tube passes entry box is grayed out. Is there some way to limit the number of tube passes for an exchanger while in Design Mode? | Solution: As shown in the figure below, it is possible to restrict the range of certain design parameters (i.e. shell diameter, tube length, tube passes, baffle spacing, baffle cut, shells in series, shells in parallel) via the Program Options | Design Options | Geometry Limits pagetab. To fix a design parameters at one specific value (i.e. number of tube passes), enter the same number for both the minimum and maximum input boxes.
Keywords: restrict, specify, shell, diameter, tube, length, pass, baffle, spacing, design, mode
References: None |
Problem Statement: Within Aspen EDR (Exchanger Design and rating), users can use user-defined (non-databank) components either as pure component or as part of a mixture. Users need to define these components firstly in Aspen Properties, and then link the Aspen Properties model with the EDR model they want to run.
Later on, users then can generate the property and can see on GUI in EDR.
However, after linking the Aspen Properties model with EDR, running and saving the EDR file once, when users re-open the EDR file, the user-defined (non-databank) components that were used in the previous run will disappear.
This | Solution: describes how to overcome this 'user-defined components disappearing after re-open' issue by using Advanced Options of Aspen Properties-EDR link inside the EDR program.
Solution
This is because the user has chosen 'Import existing Aspen Properties (.APRBKP) file' option to link the Aspen Properties model with the EDR mode.
Users should choose to use '
Keywords: User-Defined components, Non-databank database components, Aspen Properties, EDR, re-open, disappear
References: an external Aspen Properties (.APRPDF) or Aspen Plus (.APPDF) file' option to overcome this problem.
Users will need to
Fully define the user-defined (non-databank) components and property generation specifications in standalone Aspen Properties, and save it as a *.aprpdf file. More details can be found in |
Problem Statement: Aspen Properties is linked to HTFS+ as a thermodynamic package. When a user select Aspen Properties for physical property calculations, he/she should know that additional files are created by Aspen Properties.
How are Aspen Properties files managed in HTFS+? | Solution: If Aspen Properties is installed on user's computer, HTFS+ will offer Aspen Properties as a physical property calculation engine for generating stream properties, such as density, heat capacity, viscosity, thermal conductivity, surface tension and enthalpy.
Aspen Properties can be used for either for one side or both exchanger sides. For each side selected to use Aspen Properties, an .aprbkp file will automatically be created. If Aspen Properties is used for both sides, two .aprbkp files with different names will be created for the current design.
If you want to change the file name, you have to open Aspen Properties Browser, and select File | Save As to different file path. On some occasions, the browser window hides behind the HTFS+ window, but you can view the application window via the AspenTech logo (on the application taskbar at the bottom of the desktop).
To avoid any problesm, a unique file has to be used for each link (hot or cold side in a design).
When a design is passed to another user, only the .edr file is necessary. Aspen Properties will regenerate a new .aprbkp file with a unique file name for each link.
Keywords: Aspen Properties, physical properties
References: None |
Problem Statement: This Knowledge Base article provides steps to resolve the following issue:
Global Search and Tag Search in aspenONE Process Explorer don't work. However, type ahead feature from the Tag Input Line works. | Solution: 1. Run ADSAx64 As Administrator. This should resolve the missing ADSA data source for tags in the Legend.
2. Check Authentication Type on the aspenONE virtual application in IIS. Anonymous Authentication should be Enabled and Windows Authentication should be Disabled.
Keywords: None
References: None |
Problem Statement: What is meant by Wet Wall Desuperheating? | Solution: When a vapour is being cooled, the fluid in contact with the tube wall is colder than the bulk fluid. At some point, the fluid in contact with the wall could be cooled below the dew point before the bulk fluid reaches the dew point. Fluid in contact with the tube wall could therefore start to condense before the bulk fluid reaches the dew point. This concept is called Wet Wall Desuperheating.
By default Desuperheating heat transfer method is set to Wet Wall and this is likely to happen in practice. You can view/modify this option in Shell& Tube Exchanger program under Input | Program Options | Methods/Correlations | Condensation | Condensation options. The same can be done in Aircooled Exchanger program under Input | Program Options | Methods/correlations | Tube Side | Tube Side options.
When the Desuperheating heat transfer method is set to Wet Wall, the program corrects the heat transfer rate in the desuperheating zone to allow for condensation occurring at the wall.
When the alternative Dry Wall calculation is selected the program uses the single phase gas coefficient until the bulk vapor temperature reaches the dew point. Usually dry wall coefficients are lower than wet wall coefficients, and hence more conservative.
By switching between Wet Wall and Dry Wall options for desuperheating heat transfer method you can view the deference in the condensation heat transfer coefficient and overall heat transfer coefficient.
Keywords: Desuperheating, Wet Wall Desuperheating, Wet Wall, Dry Wall.
References: None |
Problem Statement: The flow of the shell side fluid can impart energy to the tubes in a heat exchanger that may cause them to vibrate.
The Tubular Exchangers Manufacturer Association (TEMA) Handbook 9th Edition in Section 6 presents a method for determining the flow induced vibration, where this | Solution: describes how the Amplitude and Acoustic Vibration analysis results presented may be interpreted.Solution
If the ?Simple TEMA Analysis? vibration analysis method has been selected from Input | Program Options | Methods/Correlations | General tab, then when a case in run, the Vibration performance is shown in Results | Thermal / Hydraulic Summary | Vibration & Resonance Analysis | Simple Amplitude and Acoustic Analysis (TEMA) tabs.
In this form there are two areas considered;
Amplitude Vibration Analysis
Vibration due to vortex shedding is expected when the natural frequency is less than twice the vortex shedding frequency. Only then is the vibration amplitude to be calculated
The amplitudes of vibration due to turbulent buffeting (or vortex shedding) are calculated and if they exceed 0.02 * tube outer diameter, then a warning is issued
Acoustic Vibration Analysis
Condition A is if the vortex shedding or turbulent buffeting frequencies are with +/-20% of the acoustic resonance, i.e., the ratio is between 0.8 or 1.2 then warnings are giving due to a lockin effect
For Conditions B Velocity, if the reference cross flow velocity is greater than the velocity determined for this conditions then warnings are given
For Conditions B Velocity, if the reference cross flow velocity is greater than the velocity determined for this conditions then warnings are given
For Condition C Parameters, if the reference cross flow velocity is greater than the velocity and the Condition C parameter is greater than 2000 then a warning is issued
Keywords: None
References: None |
Problem Statement: How can I set a VEV exchanger type in Aspen Tasc+? This exchanger style was available on early versions of the program. | Solution: To set a VEV exchanger style in Aspen Tasc+, use a BEM shell (which is the default TEMA designation for the program) and then specify a cone for both the front and rear heads; the steps are as follows:
1. In Input > Exchanger Geometry > Shell/Heads/Flanges/Tubesheets > Tab Covers set the front and the rear cover types to Cone.
2. In on Input > Exchanger Geometry > Nozzles > Tab Tube Side Nozzles set Nozzle orientation to be Axial.
3. In Input > Program Options > Design Options > Tab Geometry Limits set the minimum /maximum tube passes to 1.
Keywords: heat, exchanger, Tasc+, VEV, TEMA
References: None |
Problem Statement: In Aspen Collaborative Demand Manager, DMINIT command does not generate current month information in the DMPST set. | Solution: Although the Max Count of DMPST set is large enough, DMINIT command does not generate current month information in the DMPST set (i.e. DMINIT PERIOD=MONTHLY). This is because only the past periods will be included in DMPST set. When the period is over, it will be added to DMPST set.
The current period is not in DMPST set. It is not considered past or history until it is complete. Therefore, the command DMINIT works as intended. If there is a situation where the user needs to have a good history for an incomplete period, he can manually add an entry to DMPST set and insert his data.
Keywords: None
References: None |
Problem Statement: If I delete an existing re-alignment done in Aspen Collaborative Demand Manager, will the prior months return to the original, as if no alignment was done?
Here is the scenario:
I need to delete the following realignment existing in DM tool:
After I deleted the realignment, will the volumes of the ?adjusted history? automatically return to material code 850336 for the previous months? And starting March 2012, the volumes of the ?original history? of 850336 be automatically reflected to the same material?s ?adjusted history?? | Solution: Anytime a realignment is deleted, re-apply all must be run. After running re-apply all, yes, everything will be returned to what it would have been without the realignment.
In the example provided above, there may be other realignments affecting the same items so we can?t say specifically everything will return to normal. But if those realignments are the only realignments affecting the items being asked, the answer is yes.
Keywords: None
References: None |
Problem Statement: What is the formula for interpolating and extrapolating Viscosity in Shell&Tube/Air-cooled Exchanger? | Solution: Commonly the properties in properties table are used Linear interpolation or extrapolation when program required more temperature point data and the data input by user is insufficient.
However, for viscosity the natural log is used to interpolate or extrapolation.
Here's an example for the attached case:
In the properties for tube side, only 2 temperature points are given.
Â
We'll find the liquid viscosity at TR = 39 C for tube side.
The properties:
T1 = 28 °C
Viscosity at T1, V1 = 11.9 cp
T2 = 50 °C
Viscosity at T2, V2 = 9.72 cp
Formula:
Viscosity at TR = EXP(ln V1 + RR x (ln V2 - ln V1))
RR = (TR - T1) / (T2 - T1)
RR = (39 - 28) / (50 - 28) = 0.5
Viscosity at 39 °C = = 10.7549 cp
This matches what is reported in Calculation Details | Interval Analysis - Tube Side | Physical Properties.
Keywords: Aspen Shell & Tube Exchanger, Aspen Air-cooled Exchanger, EDR, Properties, Viscosity, Interpolation, Extrapolation.
References: None |
Problem Statement: Aspen Collaborative Demand Management consists of two modules: Aspen Collaborative Demand Manager (DM) and Aspen Collaborative Forecasting (CF), which support collaboration and exchanging information about volume and price, including overrides. This article explains the differences between the volume and price override workflows. | Solution: Background: Demand Manager uses price to calculate revenue by converting volume to revenue, using the following formula: Revenue = Volume (or Quantity) x Price (for additional details, see “Chapter 15: Configuring Units of Measure and Prices” in the Aspen Collaborative Demand Manager Implementation Guide).
The collaborative process refines the short-term demand plan (e.g., next 1 to 3 months) by using demand sensing real-time interaction between the commercial team (e.g., account managers) and the end-customer. This demand signal is used to update the statistically forecasted demand quantity or volume that is generated by the operations/supply chain team (e.g., demand planner).
In a typical negotiation process between the commercial and operations team the primary point-of-negotiation is volume or quantity. The teams can repeatedly iterate on a volume until both parties are satisfied. The operations team has the mandate to approve/disapprove the volume requested by the commercial team that is different from the forecast. In fact, the volume overrides and resulting negotiations between the commercial and operations team, on the short-term forecast, is crucial to manage a well-run Sales & Operations planning process (S&OP process).
Price is typically a policy decision and the commercial team may operate independently of the operations team using a price range that is approved by company policy taking in to account market conditions, competitive dynamics, and other factors.
Price is not a point-of-negotiation between the commercial team and the operations team. And the operations team does not approve or disapprove the price on a specific transaction. If the commercial team has significantly deviated from the price-list/range and if this deviation is meaningful to materially impact forecasted revenue (e.g., the volume is very high relative to overall business volume) then it is useful for the commercial team to indicate the new price so that the material change to the previously forecasted revenue can be adjusted using the updated price (e.g., there is agreement to supply product at 5x the statistically forecasted volume, with a 65% price discount, that increases the overall revenue forecast by 75%).
Workflows: The current workflows in Collaborative Demand Management support robust tracking of volume overrides to support the interaction and final disposition of the volume override. In the example above the commercial and the operations user can continually iterate until there is consensus to accept 5x the statistical forecast for a product from a specific customer. The approvals associated with this volume override can be viewed in both DM and CF.
This workflow is illustrated in the diagram below for Forecasted Volumes.
For price, the workflow supports the CF user to update the new price indicating the 65% discount (using the same example as above) and the updated price will be imported in to DM and the background pricing table is updated. The commercial user (CF) is not seeking approval from the operations user (DM) and the pricing override is not tracked or negotiated upon.
This workflow is illustrated in the diagram above for Selling Prices.
Important: Note that Selling Prices are not forecast; this workflow simply updates the pricing table in DM.
The DM user can view the price table in DM; however, the table does not indicate what values have been updated by the commercial user. The DM application uses this table to calculate the revenue as described above.
Keywords: Volume Override
Price Override
Pricing Override
CF
DM
References: None |
Problem Statement: Which property package is recommended for thermal oils in Exchanger Design and Rating (EDR) calculations? | Solution: It is recommended to use the Aspen Properties Wilson GLR (WILS-GLR) for thermal oils in EDR. This property package uses an enthalpy method that optimizes the accuracy tradeoff between liquid heat capacity, heat of vaporization, and vapour heat capacity at actual process conditions. This highly recommended method eliminates many of the problems associated with accurate thermal properties for both phases, specially the liquid phase.
Keywords: Mobiltherm-600, Mobiltherm-603, Mobiltherm-605, Thermal Oils
References: None |
Problem Statement: Turbulent buffeting occurs when a body is placed in a turbulent flow field and the forces on the surface of the body are changed rapidly with time and position. This is because the magnitude and direction of the velocity vector are continually changing. If the variation in force is well correlated, (i.e., the changes in force magnitude and direction along a significant length of tube are in phase) and the frequency of the variation is close to the natural frequency of the tube, tube vibration may result. A phenomenon which can cause these forces to be well correlated over a tube length is the occurrence of standing acoustic waves. This may occur when the shellside fluid is a gas or vapour. | Solution: In order to examine the possibility of turbulent buffeting excited tube vibration, the Aspen Shell & Tube Exchanger (Tasc+) program estimates the tube natural frequency (fn), the turbulent buffeting frequency (ftb) and the acoustic frequency (fa). The results are presented as ratios of the turbulent buffeting frequencies to the natural and acoustic resonance frequencies. Users can find relevant information in Vibration & Resonance Analysis output section.
Some general attempts to avoid Turbulent Buffeting:
Reduce the excitation force due to the turbulent flow by reducing the flow velocity
Increase the tube natural frequency by shortening the span lengths (for example by introducing intermediate support plates between baffles) or by increasing the tube diameter. Note that increasing the tube wall thickness has almost no effect
Increase damping by reducing the clearances between tube and baffle
Keywords: Turbulent Buffeting, Vibration, Avoid
References: None |
Problem Statement: Where can I find Polyethylene Glycol on Hysys & EDR? | Solution: Polyethylene Glycol is located on the APV73.POLYMER databank, you can add an Aspen Properties Databank Component List, then go to Enterprise Databases Tab on the component list view, add APV73.POLYMER databank, go back to selected tab and browse for PEG or glycol as shown in the following screenshot.
Keywords: Polyethylene Glycol, PEG, component, Hysys, databank, Aspen Properties, polymer.
References: None |
Problem Statement: How do I make Excel reflect the changes in EDR? | Solution: Excel and EDR link is established through built in macros in Excel template. The macros open and read values from EDR file and write to Excel. If EDR file is opened prior to running the macros, the change in EDR might not be reflected.
It is a best practice to close all EDR and Excel files and open only the specific Excel and EDR file to read and write.
Keywords: Macros, Excel template, EDR
References: None |
Problem Statement: Aspen Shell & Tube Exchanger does not allow one tube pass for G and H shells. How do I model this exchanger? | Solution: You can model this exchanger using two approaches:
1. It might be reasonable to model as an X-shell in some cases
2. The alternative method for 1-pass F,G,H shells, is to specify 2 passes, and a pass multiplier of 0.5
You can try both 0.5 pass multiplier and X-shell then compare results and (for design) choose the more conservative surface requirement.
Keywords: 1 pass, G, H shell, tube pass
References: None |
Problem Statement: How do I export my EDR file to Excel? The menu options are not active. | Solution: It is a good practice to save EDR file as soon as it is created. You cannot export the results of an unnamed EDR file.
Keywords: Excel, template, EDR, heat exchanger
References: None |
Problem Statement: What is a lock-in effect when looking at the Vibration & Resonance Analysis? | Solution: The lock-in effect is the phenomenon whereby an excitation frequency coincides with a characteristic frequency of a body to possibly cause a large amplitude of vibration. Such excitation frequencies and characteristic frequencies checked within Shell & Tube Exchanger (Tasc+) are:
? Excitation frequency: Vortex Shedding (fvs), Turbulent Buffertting (ftb)
Characteristic frequency: Nature Frequency (fn), Acoustic Resonance (fa)
Lock-in occurs when the excitation frequency comes within 20% of the characteristic frequency.
0.8 < fvs / fn < 1.2
0.8 < fvs / fa < 1.2
0.8 < ftb / fn < 1.2
0.8 < ftb / fa < 1.2
Where:
fvs - Vortex Shedding
ftb - Turbulent Buffeting
fn - Natural Frequency
fa - Acoustic Resonance
Important notes:
1. This frequency matching should be avoided in order to prevent damage due to vibration.
2. The lock-in effect occurs across a range of flow velocities bringing excitation frequencies and may be tuned out of the system, by going to either higher or lower flows, or using tube supports giving either higher or lower natural frequencies.
3. There may be more than one resonance over the operating range of the heat exchanger, due to higher natural frequencies. Shell & Tube Exchanger (Tasc+) considers only the fundamental (lowest) frequency.
4. A more serious form of vibration mechanism is the Fluid-Elastic Instability, which is not a lock-on mechanism, and thus cannot be passed through. Unlike other vibration mechanisms, lower tube natural frequencies or higher flow rates only make it worse.
In Shell & Tube Exchanger (Tasc+) on Vibration & Resonance Analysis, predicted problem areas are indicated where the frequency ratio is between 0.8 - 1.2, and is followed by an asterisk (e.g. 0.93*).
Triple coincidence, when the frequencies of three mechanisms coincide, is a potentially serious problem which you should take steps to avoid.
Keywords: Vibration, Natural frequency, Flow velocity
References: None |
Problem Statement: How do I specify Variable Baffle Pitch in Aspen Shell & Tube Exchanger? | Solution: Starting with Aspen Tasc+ 2006.5 you can specify Variable Baffle Pitch.
The use of variable different baffle pitch at different points along the shell side flow path provides the opportunity for improved designs in difficult cases; for example, where a large baffle pitch is needed in some places to keep pressure losses low, but a tight pitch is required in others keep heat transfer coefficients high. Particular capabilities with this new feature are:
1. You can specify two, three or four different baffle regions, each with a different baffle pitch and number of baffles. The baffle cuts in the various regions can be the same or different. For double segmental baffles, there is a similar facility for the inner cut, although you can also omit these and have the program estimate them.
2. For F shells, you can specify different baffle spacings in the top and bottom halves of the exchanger, or even two different spacings in each half. Similar facilities are available for G and H shells.
3. Baffle locations with variable pitch are displayed on the Setting plan, and the cuts for various baffle regions appear on the Tube Layout diagram.
4.The general variable baffle pitch capability outlined above is for simulation and rating calculations. There is also a facility to Design an exchanger with variable baffle pitch. You must specify the number of baffle regions and the ratio of the pitch in the first region (nearest the inlet) to the pitch in the last.
Keywords: variable, baffle, pitch, 2006.5, different, region, exchanger
References: None |
Problem Statement: Input Error 1805: P53: Two pressure levels at which Physical Properties are supplied for stream 1 (or 2) differ by less than 0.01%. How to fix it? | Solution: The error message is complaining about the same (or almost same) pressures level. The difference in two pressures should be at least 0.01%.
Go to Input || Property Data || Hot (or Cold) Stream Properties. Select the pressure you want to change and type a new number that satisfies the 0.01% restriction.
Keywords: Input Error 1805, P53, Two pressure levels, differ by less than 0.01%
References: None |
Problem Statement: Why do fins not change the effective surface area? | Solution: The overall heat transfer equation used is:
1/U = 1/hs + 1/ht + rs + rt.
In the above, all coefficients must be referenced to the same area (i.e. the area is based on tube side outer diameter). The adjustment for the finned area is applied to the heat transfer coefficient. If you calculate U with and without fins, you will note that the tube side heat transfer coefficients are different.
The finned area is thus reported only for the purpose of results; the effective area remains the same.
Keywords: fin, effective, surface, area
References: None |
Problem Statement: How does Aspen Shell & Tube Exchanger simulate dummy tube or rod impingements? | Solution: Aspen Shell & Tube Exchanger program can simulate dummy tube or rod impingement as follows:
First, you will need to go to Input > Exchanger Geometry > Nozzles > Shell/Tube Side Nozzles tab to specify ''Yes impingement''.
Then you will need to go to Input > Exchanger Geometry > Nozzles > Impingement tab to specify ''Dummy tubes'' or rods.
Then users can specify details of dummy tubes, like number of rows and with rods, in addition the rod layout and rod diameters.
The tubes or rod impingement can be viewed from the Tubesheet layout Results > Mechanical Summary > Setting Plan & Tubesheet > Tubesheet Layout tab
Keywords: Dummy tube, Dummy tube impingement, EDR, Shell & Tube Exchanger
References: None |
Problem Statement: Aspen Shell & Tube Exchanger shows the local average tube metal temperature along the length of the exchanger, but we can if necessary calculate the inside and outside tube metal surface temperature using the heat flux and heat transfer coefficients available from the Interval Analysis table in the program results. | Solution: Here is an example of how we can perform this analysis:
1. The information we require for the calculation is available under Results | Calculation Details | Analysis along Tubes | Interval Analysis tab as shown in the screenshot below.
2. In the first row, the point is at a distance of 8059 mm from the end, the heat flux is 6.4 kW/m2, tubeside bulk temperature is 31.11 oC and the value for tabulated local tubeside & shellside heat transfer coefficients are given.
We can obtain tubeside fouling resistance, thermal conductivity & tube wall thickness and the shellside fouling resistance from Results | Results Summary | TEMA sheet or Results | Mechanical Summary | Exchanger Geometry | Tubes section of the program.
As we know the heat flux (Q/A = q) is constant from the hot fluid through the fouling layers & tube wall to the cold fluid, this can be expressed by:
q = αT (Tbt - Tft) = (1/rT)(Tft - Tmt)= αW (Tmt -Tms) = (1/rS)(Tms - Tfs) = αS (Tfs - Tbs)
From the equation below, which shows the local overall heat transfer coefficient, the resistance to heat transfer have been normalised to the bare tube outer diameter area
with the subscripts o, i and w refer to the outer, inner and wall respectively
Keywords: Inside & outside tube metal surface temperature
References: None |
Problem Statement: As described in | Solution: 126045, users can transfer the stream physical properties from an Aspen HYSYS exchanger block into a standalone Aspen EDR file, by opening an *.EDR file, going to File | Import from | HYSYS, and selecting the correct exchanger block in the HYSYS case.
However, this behavior will mean the HYSYS file and EDR file to be opened at the same time. If the user has limited tokens that only permit one Aspen program (i.e. either HSYS or EDR) to run at a time, users will see warning and/or error messages regarding the lack of license tokens (information about ''token sever'' can be found on page 98 in the ''Installation and
Keywords: Aspen HYSYS, Aspen EDR, Data Transfer, License Error, Enough Tokens
References: Guide'' under the ''Documentation'' directory). The procedures below describe how the user can still transfer the data between the two programs. |
Problem Statement: When assessing the Shell & Tube Exchanger (Tasc+) results for flow induced vibration, a condition known as triple coincidence should be looked for. | Solution: Triple coincidence is when a single tube suffers two (or more) vibrations, Lock-In Effects, at the same location along it's length (for example: fvs/fn and ftb/fn resonance at the inlet for the first tube row in the bundle). In this condition the tube is being excited by two vibration mechanisms at the same time and at the same location.
fvs = fn = fa, (or ftb = fn = fa)
Where:
fvs - Vortex Shedding
ftb - Turbulent Buffeting
fn - Natural Frequency
fa - Acoustic Resonance
Vibration calculation methods do not yet model any interaction of vibration mechanisms. It is strongly recommended that triple coincidence is avoided.
Keywords: Triple Coincidence, Frequency, Vibration, Lock-in effects
References: None |
Problem Statement: In Aspen Shell & Tube Exchanger when using the ?find flow? option for a thermosyphon, the flowrate through the exchanger is calculated from a pressure drop balance around the piping circuit and the heat exchanger.
When in ?thermosyphon? mode the geometry of the heat exchanger must be specified along with the pressure losses in the pipework connecting the thermosyphon reboiler to the column. These pipework pressure losses can be specified in two ways from Input | Exchanger Geometry | Thermosiphon Piping | Thermosiphon Piping tab for the ?Pipework loss calculation;
Percentage of liquid head: Specify the pressure loss as a percentage of the liquid head driving the thermosiphon flow - derived from the difference in height between the liquid surface in the column and the exchanger inlet. This has the benefit that no information need be provided about the actual pipework geometry, making the option useful at early stages of a Design.
From pipework: Specify details about the pipework, both inlet to the exchanger from the column, and outlet from the exchanger (return to the column). This option is recommended for Simulation calculations which aim to find the thermosiphon flow.
The pressure at the liquid surface in the column ( Input | Problem Definition | Process Data ) is specified and from the liquid height of this surface above the inlet to the exchanger, the hydrostatic head can be determined to give the increase in pressure at the exchanger inlet (height x density of fluid x gravity). This increase in pressure will mean the inlet fluid is now sub-cooled, and as the fluid enters the thermosiphon it is first heated to the saturation temperature before vaporisation occurs. As the fluid evaporates, the local density decreases and this difference in density between the inlet circuit and heat exchanger causes the thermosiphon flow.
To determine the thermosiphon flowrate, Shell & Tube Exchanger takes an estimate of the flowrate and performs a pressure drop calculation (accelerational, frictional and gravitational) around the complete thermosiphon circuit (the inlet circuit, the heat exchanger and the outlet circuit). The pressure at the liquid surface of the column is assumed to be the same as the exit from the outlet circuit (neglecting accelerational/frictional pressure drops in the column as the diameter is assumed to be large and also the gravitational component due to the vapour is assumed negligible) when the unit is operating at the thermosiphon flowrate. If these pressures do not match, then a new estimate is taken for the flowrate and the pressure drops recalculated until they agree.
The geometry of the heat exchanger is entered together with the inlet/outlet piping. The hydraulic performance on the piping circuits is very important in determining the thermosihon flow. If the from pipework option is used, the piping element components must be specified, where elements such as bends or straight lengths of pipe of a given diameter can be entered together with a general element that may be used to model a valve for example. For two-phase flow in the outlet circuit it is important to distinguish between horizontal and vertical pipes. In addition, all pipes and fittings should be entered in the order that they are encountered. The lengths of the pipe etc in the outlet circuit should not simply be summed together as a single length as the case with the inlet pipework.
From Results | Thermal / Hydraulic Summary | Pressure Drop | Thermosiphon tab the total pressure drops in the inlet/outlet circuits and the exchanger are presented, where when the case has converged should sum to zero. In this table, the unaccounted losses shown should be negligible where when given should be due to convergence tolerances to match the values.
The unaccounted losses arise when the ?fixed flow? calculation is used where the entered flowrate specified in general will not give a pressure balance around the thermosiphon circuit. This appears as an unaccounted pressure change in the inlet/outlet circuits. | Solution: With the ?find flow? option, the unaccounted losses should be negligible. However, if the values are large then this may be due to using the Advanced calculation mode in Input | Problem Definitions | Application Options.
There are two options to minimize these unaccounted losses;
From the Warning & Messages, there may be an operations warning 1371/1372 that the calculated pressure drop exceeds the maximum allowable pressure drop. If this is the case then there are twoSolutions;
o Increase the allowable pressure drop entered in the Process data to be greater than the calculated pressure drop
o From Input | Program Options | Calculation Options for the Pressure Drop Options set the pressure drop calculation for the cold side to ?predict outlet pressure?
Set to Standard mode, which does not have the options to limit the pressure drop calculations.
Keywords: Thermosiphon. find flow option
References: None |
Problem Statement: Each release of an AspenTech program has a unique reference number, that is a series of digits, giving the version, cumulative patch and build number. This | Solution: describes how to check the numbers in the Aspen Exchanger Design & Rating (EDR) suite of programs.
Solution
Open the program, go to main menu on top of the diagram, and then select Help > About Aspen Aspen Exchanger Design and Rating
A separate window will pop up.
Check out the numbers in the brackets, which are of the form (Version Number . Number . Cumulative Patch . Build number). The latest patched build number for each version should be:
'2004.2 (13.3.3.1865)'
'2006 (20.0.6.2134)'
'2006.5 (21.0.2.538)'
'V7.0 (22.0.2.874)'
'V7.1 (23.0.2.1145)'
'V7.2.1 (24.0.1.2156)'
'V7.3 (25.0.0.2677)'
'V7.3.1 (25.0.1.3063)'
Please be aware that emergency patches/hot fixes may not be reflected by changes of the build numbers.
Please note that AspenTech may have released cumulative patches since thisSolution was written, where it is advisable for users to keep checking any potentially up-coming patches to see if your program has been fully patched. The patches can be found and downloaded from Aspen?s support website at http://support.aspentech.com. For details can be found in TechnicalSolution 131394.
Keywords: EDR, Build number, Cumulative patches, CPs
References: None |
Problem Statement: Due to the fabrication of heat exchangers, tubes in similar locations within the bundle may have quite different damping due to the assembly. Some tubes maybe tightly contained by the baffles (heavily damped) whilst an adjacent tube may be loose and will vibrate if shaken (lightly damped).
The tube vibrations are damped because energy is dissipated by:
Material damping: the natural energy dissipation which occurs when a tube is flexed
Baffle support damping: caused by friction between moving parts in the tube supports and can vary considerably depending on the accuracy of assembly of the heat exchanger
Squeeze-film damping: dissipation of energy due to periodic displacement of fluid from the tube/baffle gap as the tubes vibrate
Fluid damping: bulk fluid damping due to viscous effects of moving the tube in the fluid
For this reason, we look at three damping values ( or log decrements) representing heavy, medium and lightly damped when analysing the FEI by Aspen Shell & Tube Exchanger. In additions we also look at the geometry and make an estimate of what the actual damping may be for the tube location. | Solution: If the ?Full HTFS Analysis? vibration analysis method has been selected from Input | Program Options | Methods/Correlations | General tab, then when a case in run, the Vibration performance is shown in Results | Thermal / Hydraulic Summary | Vibration & Resonance Analysis | Fluid Elastic Instability (HTFS) and Resonance Analysis (HTFS) tabs.
For FEI, warnings are issued based upon the ratio of the flowrate / critical flowrate as follows;
Yes if W/WC >1 for heavy damping
Yes, if W/Wc>1 for medium damping
Yes if W/Wc>1 for estimated damping
Possible if W/Wc >1 for light damping only
Keywords:
References: None |
Problem Statement: How does Aspen Shell & Tube Exchanger calculate the Tube Layout? | Solution: There are three steps in determining the tube layout:
1. Determining the outer limits of the bundle ? and the overall number of tube rows and columns
2. Determining the number of rows and columns in each pass region, and hence the location of pass partition lanes
3. Determining the location of each tube in each pass region.
The ?outer limits of the bundle? mean not only the outer radial limit determined by the shell-bundle clearance, but also the limits at the top, bottom, and two sides. Initial estimates of the limits come from the space required under shell side inlet and outlet nozzles, but exact values, consistent with an integral number of tube rows and columns, are determined by the tube pattern and pitch, and by the width of pass partition lanes, if any. Pass partition lane widths need to be larger if they must allow for U-bends, longitudinal baffles, or cleaning lanes (in 45 degree patterns).
For staggered tube patterns, the bundle outer limits can also be affected by the input for tube layout symmetry. This can adjust the number of tube rows and or columns, if necessary, to give tubes along the vertical and/or horizontal tube diameters.
Given the bundle outer limits, and hence the total number of rows and columns, the number of rows and columns in each pass region is set to equalize, as near as possible, the number of tubes in each pass region. This is done automatically by the program. With the Specify Pass Details layout option, however, you can explicitly specify the number of rows and columns in each pass region ? and thus set deliberately unequal numbers of tubes if you wish.
Staggered layouts have tubes in alternate locations (meaning every other location) on the underlying grid of rows and columns. When possible, this is selected to optimize the number of tubes in each pass region. When the locations in adjacent pass regions are interdependent, for example with U-tubes or cleaning lanes, the overall bundle count is optimized.
Keywords: tube layout
References: None |
Problem Statement: How and when do I use the Prune option in Aspen Collaborative Demand Manager? | Solution: Aspen Collaborative Demand Manager works with the data that is imported into the model from flat text or excel files or from any other Database. These imported data are used as attributes to perform Aggregation, which in turn helps in presenting the forecast in the required format. Aggregation is purely based on Indices.
Index of an entry = Position of that entry - 1
In a set or table if an entry is in the second row, then the index of that entry is 1.
So if a new entry is added or removed directly to any of the attributes, then the aggregation malfunctions causing errors in many features. Hence to remove such entries, the Prune option should be used.
Prune option is available in the ATTDEF table. ATTDEF table has Attributes (ATT) as the Row Set and Definitions (ATTDEFC) as the Column Set. PRUNE is one of the options of ATTDEFC.
Empty records may enter into the model without knowledge - for example: through empty lines in the input text files. Such records can cause trouble when data is published from CDM to Collaborative Forecast (CF). In such scenarios, Prune option can be turned on, by changing the value to YES for that Attribute in ATTDEF table. Prune will remove the empty record from that Attribute if it is not used by any other attribute for Aggregation.
If Prune option does not remove any particular record in any attribute, then deeper analysis on why that record initially appeared and how it correlates to the other attributes needs to be figured out. That attribute needs to be removed methodically from the model.
Keywords: None
References: None |
Problem Statement: This is to follow up on the Introduction of Aspen Licensing Dashboard- How to set it up on the client PC | Solution: Please see attached document on how to set up the Aspen Licensing Dashboard on the client PCs.
Based onSolution ID:136456
Keywords: Aspen Licensing Dashboard, Installation & Setup, Licensing, Server, Usage
References: None |
Problem Statement: How do I test my connection to the Support site trough aspenONE Exchange? | Solution: Sometimes due to internet connection and company policies some ports and IPs need to be active. To start with the diagnose we recommend the users try the following:
1. Verify Aspen HYSYS V8.4 or V8.6 is updated with all the security patches.
           * For HYSYS V8.4 please refer toSolution 141801
           * For HYSYS V8.6 please refer toSolution 141458
2. Check the connection directly from HYSYS. Please go to Resources tab > aspenONE Exchange ribbon > All content, in the right hand of the screen you should see “Log in� link, please use the support page credential, just below it there is a settings button, please click on that. The aspenONE Exchange Settings window appear, please click on “Check Connection� a window like the following should appear
Please click in copy to clipboard and send it to [email protected]
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Keywords: connection, test
References: None |
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