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Compatibility Notes for Aspen Plus V8.0
This section describes the differences that you might encounter between Aspen Plus V8.0 and Aspen Plus V7.3.2. In most cases, previous Aspen Plus input files and backup files are completely compatible with Aspen Plus V8.0.
When you open a file from a previous version, Aspen Plus displays the Upward Compatibility dialog box. If you select Maintain Upward Compatibility for Features Listed Below then Aspen Plus ignores the new features in all the areas mentioned on the dialog box (which may include new pure component databanks, property methods, built-in parameters, ADA/PCS procedures, calculated molecular weights obtained from formulas, and checking of user-specified sequence, depending on the version of Aspen Plus used to create the file).
Costing results from Exchanger Design & Rating or Economic Evaluation may change from one version to the next due to updated cost data.
New features in other areas, as noted below, may still cause different results in the new version. These changes may have greater impact in flowsheets with loose tolerances due to convergence paths being different. AspenTech makes every effort to avoid making changes that result in incompatibilities with previous versions. The changes discussed in this section were necessary to correct problems (such as wrong results), to implement new features, or to improve ease-of-use.
The most important areas where you might encounter differences between Aspen Plus V8.0 and earlier versions are:
Fortran Compiler
Aspen Plus V8.0 was compiled with the Intel Fortran compiler XE 2011 (version 12) and Microsoft Visual Studio 2010. User Fortran models compiled with different compilers or compiler versions may not work, or may run but not be able to write to the Aspen Plus history file, report file, and control panel. See Chapter 1 of Aspen Plus User Models for more details.
In version V7.3, we switched from using the gcpp preprocessor to the preprocessor built into the Fortran compiler. If you followed the guidelines in Aspen Plus User Models for user subroutines, writing includes in the format
#include "filename"
and starting in column 1, then you should not encounter any problem, but if your code depends on other formats for include statements, you may need to change them to this format. If you use include statements in inline Fortran (such as in Calculator blocks), use this format and start it in column 7.
Solids Unit Operations
The overall efficiency for Screen is now calculated in a different way which can be extended consistently for multiple-deck screens. The efficiency value will be different than that calculated by previous versions.
The default outlet pressure specification for Dryer is now zero pressure drop instead of 1 atm outlet pressure. This will affect Dryer results in cases where no pressure specification exists and where the inlet pressure is not 1 atm.
Dryer now has separate inlet stream ports for solid and gas feeds, each of which can take only one stream. Models from previous versions with multiple streams connected to the single feed stream port will load with only the first stream connected to the solids port, which may make the block incomplete if any disconnected ones are feed streams. Please choose the correct port for each stream and reconnect them appropriately. In some cases you may need to insert a Mixer to combine streams before feeding them to Dryer.
The new feature in ClChng allowing different solid substreams to be mapped into one another may result in different results in the case where the inlet and outlet streams contain substreams of the same type (such as both having conventional solid substreams) but of different IDs, and the inlet stream was not empty. Now, in this case, the substream will be copied to the extent possible, instead of being dropped and created empty in the outlet stream.
When streams containing solids in the MIXED substream enter a solids unit operation in which particle size distribution (PSD) is required, the PSD of the first solid substream with a PSD will be applied to those solids. In previous versions those solids were ignored. This will produce different results but they will be more sensible results since those solids in the MIXED substream are treated as solids for other purposes.
Rigorous HeatX Results
Results for rigorous HeatX using Aspen EDR has been updated to more closely match the results provided by the Aspen EDR programs. Some redundant results have been eliminated. Missing results on the Shell & Tube Results form when there are multiple shells in parallel or series have been added. The LMTD (Corrected) result for air-cooled HeatX blocks now matches the Effective MTD result from AirCooled.
Also, when modeling a thermosiphon with the rigorous model, when the Circulation type is set to Circulated (meaning to vary the flow rate to meet the pressure balance), although the varied flow rate was used in Aspen Plus, the results of the thermosiphon on the Shell & Tube Results form incorrectly showed the original flow rate. This is now fixed.
Removed Local Units for Pres-Relief
The Pres-Relief block had local units on the Information sheet in V7.3.2 just for the stop criteria. Now these variables follow the global unit set and the units are displayed on the form where they are specified. In files loaded from previous versions these variables will be updated to the global unit set.
Jet Flood Methods
In previous versions, for calculating flooding in tray distillation columns, some jet flood methods were allowed for tray types where they were not applicable. This may have led to incorrect results regarding flooding in columns configured this way. Now only Glitsch methods are allowed for Glitsch trays, and Kister is not available for bubble-cap trays. Some files from previous versions may load as incomplete due to the stricter checking of tray types.
Eckert Pressure Drop Correlation for Packing
An error in the Eckert pressure drop correlation for packed columns was fixed. In packed columns using Eckert pressure drop, you will likely see different pressure drop and fractional capacity results.
EO Input for Analyzer Fraction Variables
When files from Aspen Plus V7.2 or earlier which contain EO Input for fraction variables in an Analyzer block are imported into a later version, and the file is using the ENG units set (or some custom units sets), this input will be interpreted correctly and needs to be fixed.
Fraction variables in Analyzer blocks used to be untyped in EO, meaning that they had no units and were always treated as fractions. Starting in V7.3, for consistency with other fraction variables, these variables were given the physical type CONTENTS. If you are using an SI or Metric based units set, the default unit for CONTENTS is FRACTION, so there is no problem. However, if you are using the ENG units set, the default unit for CONTENTS is PERCENT. The result in this case is that a specification which used to be 0.1 fraction will now be 0.1 percent, the equivalent of 0.001 fraction. You can fix this by either changing the specification to 10 percent or changing the units for the variable (so the specification is once again 0.1 fraction).
Multiple Hydrates in EO
EO models that handle solids cannot directly handle multiple hydrates for the same compound (including the unhydrated form). In previous versions, simulations containing multiple hydrates would often fail to converge in EO.
Now, the hydrate form that exists at initialization is used and others are not allowed to precipitate. The hydrate form is chosen separately in each block and stream where the compound exists. As long as the EO solution does not vary too much from the initialized value, the result should be valid. This may lead to different results in some cases, but it should converge much more consistently. Sequential modular hydrate calculations are unchanged.
Heater EO Variables
In a previous version, a change was made that caused the names of some EO variables for Heater to change, but only for blocks with the EO formulation set to EOPML on the block's Block Options | EO Options sheet, under Additional Options. (Note that Standard should always be used for new models; EOPML is for compatibility with older models.)
The change affects the flash variables created when the Heater has a subcooled specification. These variables should be named in the form blockid.BLK.BUB_x where x is TEMP, PRES, ENTH, MVOL, or any of the variables created by EO flashes. In versions from 2004.1 to V7.3.2, they were incorrectly named blockid.BLK.DEW_x instead. These variables are now once again named with BUB, reflecting the nature of these variables representing a bubble point state.
This change will only affect you if you have made specifications for these EO variables or you use EO variable files to export and import data.
Regression Results
In previous versions, after a property regression of type Evaluation, the estimated or calculated values on the Regression | Results | Residual and Profiles sheets may not have been correct. This would lead to these values differing from the results of a property analysis calculation using the same parameters. This issue has been fixed; in affected cases you may see different estimated or calculated values.
Property Set Properties
Vapor pressure Property Set property PL can now be calculated by equations of state. In previous versions Antoine was used instead when you configured PL to be calculated by an equation of state, and in such simulations you will see different results for PL. This only affects the Property Set property (mainly used for calculations such as property analysis), not simulation results.
SRK Models Water Option
Option code 3 for SRK-based models, which determines how water properties are calculated, now defaults to 0 (calculate water properties using the equation of state). In previous versions the default was 1 (calculate water properties using steam tables), but this option has been observed to cause unstable results in some cases, especially at very low water concentrations. Results will be different for some simulations using these models and water with the default option code. You can change the option code to 1 to restore the results from previous versions.
Units of Measure
The pressure unit mbarg (millibars gauge pressure) appeared in previous versions as Mbarg, which may have led you to mistakenly believe it represented megabars. It in fact always represented millibars. The display of this unit has been corrected.
Include Streams and Exclude Streams Now Only Apply to the Report File
The stream report options Include Streams and Exclude Streams in Setup | Report Options | Stream were intended to apply only to the report file and not to the stream results shown in the stream results forms. However, they were also applying to stream results forms and made it impossible to get the results of excluded streams in any way. Now these features actually only exclude streams from the report file. Also, if you clear the option on this sheet to generate the standard stream report, that report will be excluded from the report file but you will get basic stream results (composition as mole flow only, no property sets) in stream results forms.
Retired Features
PFD Mode (which formerly let you make an alternate version of the process flowsheet to depict equipment in the plant not modeled in the simulation) is no longer available.
Aspen Properties Web Interface is no longer available. Aspen Mobile Properties replaces this feature.
The Assay Data Analysis run mode in V7.3 and earlier was replaced with the Analysis run mode in V7.3.2. This is mostly compatible, but some files using this run mode may load as incomplete due to no property method being specified. The special handling of properties in ADA-only runs is no longer supported.
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