Example problem 6 will guide you through the construction of two separate radiation enclosures, one for gray body radiation and another for wavelength dependent radiation. The radiation resistors are developed using the VIEWFACTOR program.

Convection or conduction requires that a material is present for the transfer of heat energy to occur. A material, however, is not needed for a surface to transmit heat to another surface by radiation. Two types of radiation supported by Patran Thermal are gray body and wavelength dependent. A gray body surface must have the absorptivity equal to the emissivity and that emissivity is constant over the entire temperature range. Wavelength dependent radiation is a significant extension of the gray body theory such that the normal radiosity is divided into discrete frequency bands with the emissivity and transmissivity assumed to be gray within these frequencies. The VIEWFACTOR program then develops the radiation view factors, from which radiation resistors are developed which Patran Thermal can incorporate into the solution.