Stream Thermodynamic System
In PRO/II, the selection of thermodynamic methods has been simplified by the concept of the method set. Method sets consist of predefined thermodynamic methods for K-values (VLE and LLE), liquid and vapor enthalpies, entropies, vapor fugacities, and densities. Numerous predefined sets are provided. Multiple thermodynamic method sets may be selected for each flowsheet. For example, a default set may be specified for the overall flowsheet and other method sets used for individual units.
Specifying the Thermodynamic Method for a Stream
The Thermodynamic Method Determined from Connectivity
By default, each product or sink stream on the flowsheet (PFD diagram) uses the Thermodynamic System defined for the unit operation from which the stream emanates. All feed and source streams use a set of inheritance rules. In general, a feed or source stream will inherit the thermodynamic method of the unit operation to which it is connected.
Individual Thermodynamic Methods
If you have defined more than one thermodynamic system for your flowsheet simulation, you may specify which of the defined thermodynamic systems is to be used for the thermodynamic calculations for individual feed or source streams. The thermodynamic system used for all product or sink streams leaving a unit operation that do not go to another unit operation is the same as that specified for the unit operation from which the stream emanates and it cannot be overridden.
To change the thermodynamic system used for a specific source or feed stream, select the desired thermodynamic system from the list of available choices within the desired stream. The available choices are:
Determined from Connectivity: The method is determined as discussed above.
Default: The method specified as the Default Thermodynamic
System as defined in the Thermodynamic Data Window.
Explicitly Specified: The method explicitly specified as discussed above.
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