Radiation between fluid domens
 

It is prototyped issue of the heat by radiation between fluid domens, in one domen1 heated gas in the other domen2 flow of the hard material (with very small viscosity).
Whether to in this case install adsorption coefficient and scattering coefficient for hard material? and accordingly model radiation for this domen2?
And where find importances these coefficient for material (clinker, cement concrete, sand)?