The thermodynamic system used for the equilibrium calculations is defined in this window. If two liquid phases are expected to exist in the column, a suitable activity method must be defined for the calculations.
Usage
From the Column Main Window, push the Thermodynamic Systems button.
Thermodynamic System Specification
By default, the thermodynamic system which was defined as the default system in the Thermodynamic Data Window is used for all the trays in the column. A different method may be selected from the list of the methods specified in the Thermodynamic Data window. Alternatively, systems may be defined for individual sections of the column.
Thermodynamic System for Individual Sections
If different systems are defined for each section, the systems are entered from the top tray downwards in the table. In the first row, enter the last tray for the top section and select the thermodynamic system which is to be used from the drop-down list. The next section starts at the next tray down the column. Successive rows of the table are used to define systems for other sections. If the last tray number specified is not the bottom tray in the column, the default thermodynamic system will be used for the bottom section.
Chemical VLLE Test Options
This option is only available when Chemdist is selected from the Column Algorithms on the Column Main Window, thermodynamic systems are defined for individual sections of the column and at least one thermodynamic system defined is a VLLE Model and one is a VLE Model.
PRO/II initially determines whether a tray exhibits VLLE behavior using the thermodynamic system defined for that tray. If Check for VLLE on VLE trays is checked, PRO/II also checks for VLLE behavior on trays that have a VLE thermodynamic system. The Anticipated Number of Trays with VLLE entry specifies how many VLE trays will be checked for VLLE behavior. The column will be re-solved for each VLE tray up to this limit.
The default thermodynamic VLLE system (used for the checks) is the VLLE system specified nearest the top of the column. A different system may be selected from the list of defined VLLE systems.
Click RATEFRAC options... to pop up Column - VLLE Test Data dialog box.
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