7.6. Generate RGP File

You can generate Real Gas Property (RGP) files from the Generate RGP File dialog box in CFX-Pre.

Select Tools > Generate RGP File to open the Generate RGP File dialog box, the settings of which are described next.

Select Fluid By has the following options:

  • Short Name

    Select the Short Name of an available fluid for which to generate RGP data. The list of available fluids is from the NIST REFPROP database.

  • Long Name

    Select the Long Name of an available fluid for which to generate RGP data. This option is otherwise similar to the Short Name option.

  • File Name

    Specify a file name for Fluid File, specifically the name of a *.FLD file, which contains a definition for a pure fluid.

    Optionally click Browse   next to Fluid File to open the Select File dialog box.

  • Chemical Formula

    Select the Chemical Formula of an available fluid for which to generate RGP data. This option is otherwise similar to the Short Name option.

After a fluid is selected, basic information about that fluid, and the ranges of temperature and pressure for which RGP data could be generated, appear on the Generate RGP File dialog box, below the fluid selection.

RGP File specifies the name of the RGP file to write.

The Import File After Generation check box is available if there is currently a case open in CFX-Pre. If this check box is selected, the RGP file is imported into the current case for convenience.

The RGP File Type setting controls which phases are exported. The options are:

  • Combined (Liquid and Vapor)

    Specify Comp. Name Prefix to help name the fluids that appear in the generated RGP file. With "<prefix>" representing Comp. Name Prefix, the liquid is named "<prefix>L" and the vapor is named "<prefix>V".

  • Liquid Only

    Specify Liquid Name to name the fluid that appears in the generated RGP file.

  • Vapor Only

    Specify Vapor Name to name the fluid that appears in the generated RGP file.

If the Include MetaStable State check box is selected, metastable property data is included in the RGP file. Including metastable property data is recommended for cases with non-equilibrium phase change. Including metastable property data is not recommended for:

  • Cases that involve equilibrium phase change.

    Metastable property data does not need to be included if the generated tables are only going to be used for equilibrium phase change simulations.

  • Cases that do not involve phase change.

    Such cases only need data for one state (for example, gas).

The RGP data is expressed as a table within the exported RGP file. The following settings control various aspects of how the RGP data is tabulated:

  • The Table Resolution setting controls the overall size and resolution of the property tables. The higher the resolution, the larger the size. The options are:

    • Low

    • Medium

    • High

    • Custom

      The Interpolation Error setting specifies the error tolerance for the RGP data. Reducing the error tolerance results in a higher table resolution.

  • The Set Table Limits group of settings can optionally be used to override the default table limits, for example to reduce the table size thereby reducing the time required to compute (and later solve with) the table data.

For details on using RGP files, see Loading .rgp files in the CFX-Solver Modeling Guide.