Radiation coupling in S2S model in Fluent
 

Hi, I am using S2S radiation model in Fluent.
As per theory, using radiosity matrix equation the radiosity values are calculated at the surfaces that participate in radiation exchange.
But, how these computed values are coupled to the fluids energy equation?
Is it through a boundary condition (energy balance at the participating surfaces) or through a source term in the energy equation?

I request any one to help clarify this.

Thanks in advance!
Vidyadhar