Use the Heat Transfer with Surface-to-Surface Radiation multiphysics coupling () to account for heat transfer by radiation on boundaries, when the surrounding medium does not participate in the radiation (transparent medium).

on the side of the boundary where the radiation is defined, where ε is the surface emissivity, G is the irradiation, and eb(T) is the blackbody hemispherical total emissive power. Where the radiation is defined on both sides, the radiative heat source is defined on both sides too.

The Label is the default multiphysics coupling feature name.

The Name is used primarily as a scope prefix for variables defined by the coupling node. Refer to such variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different coupling nodes or physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first multiphysics coupling feature in the model) is htrad1.

This section defines the physics involved in the Heat Transfer with Surface-to-Surface Radiation multiphysics coupling.

Select the Heat transfer interface associated to the temperature dependent variable. Select the Surface-to-surface radiation interface associated to the radiosity variable.

If Default domain opacities is From heat transfer interface, the opacity depends on the domain feature:

Note that when a Heat Transfer in Shells interface is selected under Heat transfer in the Coupled Interfaces section, no domain node is available. Therefore, the default opacity set in the Surface-to-Surface Radiation interface is used: all surrounding domains are considered as transparent.

If Default domain opacities is Transparent, all domains are considered transparent by default.