Radiation Equilibrium Thermal Wall Condition
I want to model the wall in my simulation in the state of radiation equilibrium.
In a radiation cooled adiabatic wall, the heat flow of the air and the heat radiation of the wall cancel each other out and the heat flow into the wall is therefore zero. The heat radiation can be calculated according to the Stefan Bolzmann Law (see picture). In Fluent under Boundary Conditions -> Wall -> Thermal, it is possible to select Radiation. But there it is only possible to select the External Emissivity. But as I understand I need the internal Emissivity. Also, which value should the external radiation temperature be defined as? To my understanding this temperature is not known.
Is it possible to implement this thermal wall BC in Ansys Fluent easily or is it necessary to write a UDF?
Thank you very much for your support!