The boundary condition options that appear will depend on the type of model you are using. Choices will come from the following:
This setting represents the effective blackbody temperature of any bodies
beyond that boundary. For example, in the instance that a body has a wall
temperature of 
and an emissivity of 
, in
the absence of any attenuation, the effective blackbody temperature is given by
. This temperature is not necessarily the same as
the local temperature.
The local fluid temperature must be used to account for the incoming radiation energy. It is extremely useful for outlets or openings when the external blackbody temperature is either unknown or much lower than the expected outlet temperature.
Specify the mean radiation intensity only, and it is only supported by the P1 model.
You can specify the radiative heat flux directly, and it is only supported by the P1 model.
At opaque boundaries, the emissivity must be supplied. It can be set as a function of spectral variables using CEL expressions when using the Multiband spectral modeling option.