New and different Patran Thermal radiation resistors may be created by changing the Patran Thermal material property definitions in the VFAC templates and in the material property data files where the MPIDs are defined, typically in the Patran Thermal file MATDAT.

If the VFAC templates are changed, then Viewfactor must be used to create new Patran Thermal radiation resistors and radiosity nodes.

If the VFAC templates are not changed and only the Patran Thermal material property definitions are changed (but not the MPIDs), then you do not need to recreate the Patran Thermal radiation resistors and radiosity nodes. This is because Viewfactor only uses the VFAC templates and the raw viewfactor data to create the Patran Thermal radiation resistors and radiosity nodes. If the templates and viewfactors are not changed, the resistor will not change.

Changes in the VFAC templates are typically entered from a text editor. The VFAC templates are described more fully in Relationship of VFAC LBC Data to VFINDAT File Data, 51 and in the Patran Thermal User’s Guide.

If the VFAC templates are changed, then Viewfactor must be rerun to recreate the Patran Thermal radiation resistors and radiosity nodes.

Note that when you change the VFAC templates you need not recalculate the viewfactors. You only need to recreate the resistor data. Instructions for running Viewfactor in this mode are given in Compatible VFAC LBC and Template Data, 121.

Once again, remember the compatibility requirements for VFAC LBCs and VFAC templates referred to in the previous section and Patran Thermal TEMPLATEDAT Files for Surface Property Description, 52.

The material property definitions are part of Patran Thermal. Refer to the Patran Thermal User’s Guide for more information. As long as the material property ID, MPID, and VFAC template are not changed, the existing Patran Thermal radiation resistors and radiosity nodes will be valid. This allows for wide latitude in material properties, provided compatibility was insured when the model was created. For example, a material property which was originally modeled as a constant in its MPID definition may be changed to a temperature dependent function merely by changing it's MPID definition in the Patran Thermal MATDAT file. No changes need to be made to the radiative resistors or radiosity nodes.

If you wish to recreate Patran Thermal radiation resistors and radiosity nodes and not recalculate the viewfactors, then the run control parameter, $RUN_CONTROL:, in the VFCTL file must be set to the value 2.

All Viewfactor jobs are submitted in the same manner. Refer to Submitting a Viewfactor Job for Analysis, 98 for detailed instructions on submitting the Viewfactor job to recreate the Patran Thermal radiation resistors and radiosity nodes.