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User Value Objects in ProMax 2.0 (by Lili Lyddon)
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Location: Blogs The BR&E Blog |
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| Posted by: BRE Blogger |
Tuesday, March 13, 2007 12:35 PM |
New in ProMax 2.0 is the ability to create User Value objects which are values or properties defined by the user. Related User Value objects are grouped into User Value Sets as defined by the user. Any of the predefined unit combinations present in ProMax (e.g., mass flow rate, temperature, density) may be selected for a user value. Alternatively, a custom unit may be defined which combines standard units in ProMax or utilizes unknown units such as currency. The results from a user value can be displayed on the flowsheet in Visio or utilized in dependent calculations in specifiers and solvers. A User Value is typically a property defined by the user which is not available in ProMax. Examples of User Values might be steam rate to the stripper reboiler in an amine unit (lb steam per gallon solution circulation), circulation rate in a glycol dehydration unit (gallon glycol per lb water in the wet feed), a component ratio, acid gas composition (grains per gallon or grains per standard cubic foot,) etc. A User Value can also be a reference value, composition, or property.
Authored by Lili Lyddon (BR&E Technical Support and Help Author) |
| Copyright ©2007 BRE Ltd. |
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RE: User Value Objects in ProMax 2.0 |
By sbolman on
Thursday, May 08, 2008 8:40 PM |
I have found User Value Objects to be very useful in a number of ways.
A.) The are a great location to control data input. I have template process units (glycol units for example) and run simulations on a wide variety of applications. Generally the design parameters given provided by the customer include standard gas volumetric flow, supply pressure, temperature and compositions, and the outlet gas spec (and incomplete list, but you get the point).
In my template flowsheets, there are User Value Objects for each of these universal design parameters. Each of these User Value Objects are then assigned a short moniker which is then referenced by a simple specifier to assign the value into the correct stream or block. In this way I am able to better manage these universal parameters. I also include a property table which prints out these "Input Parameters" on the output.
B.) They are also the best location to store specifiers and solvers (calculators).
By assigning these calculations to a User Value Object AND assigning a short moniker to the User Value Object THEN using a simple specifier to pull the moniker value from the User Value Object into a Promax shape field, the calculation becomes independent of any Promax Shape.
EXAMPLE A: I will frequently create a collection of stream compositions (based on operational cases), but all of these streams will have the same dependent parameters (temperature, pressure, flowrate) calculated from a variety of values (monikers) obtained from Promax. The independent location of the specifier (in the User Value object) allows simple solvers to reference the Short Moniker ("SetP" for Set Pressure) which point to the User Value. In this way only the short moniker "SetP" need be referenced by the specifier and the specifier formula is simply "SetP".
This independence of location also permits easy reassignment of Solvers.
EXAMPLE B: There are frequently multiple locations to set flows (inlet stream or outlet stream) one of which is usually better than the other but this is not always the same and not always evident at first inspection. By placing the solver in a User Value instead of in a single field in a single stream, the solver can be assigned (again via a simple solver and short moniker as above) to either mass flow, volumetric flow; upstream or down stream. Usually no modification to the solver is required.
I could come up with other benefits but it will be left to others to continue...
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