Radiative thermal transfer

Hi Comsol users,

I am solving a thermal stress problem and I actually have some questions regarding the radiative heat transfer model.
So I am modelising the behaviour of a brick (the one used in masonry constrction) at high temperature.
The brick has many cavities that are filled with air.
Here is a picture of a typical brick I modelise:
www.villas-mediterranee.com/files/news/BRIQUE.jpg

It’s very important for me to take into account radiative heat transfert.
So I am not sure how to do that :
- Does the module « Heat Transfer in Fluids » take in account that kind of heat transfert.
- Or do I need to use the option « Surface-to-Ambiant Radiation », in which case I don’t know what value to set in Tamb (since actually that temperature is not fixed and varies).

Thanks in advance,
Ahmed