Different surface incident radiation between surface and surface-shadow
 

Hi!
I have a surface between two different material (Air and steel) so fluent generated two surfaces (surface and surface-shadow). There is another surface at high temperature near the first one. can someone explain me why i have two different values of the surface incident radiation between the surface and the surface shadow? particularly the value of the air side is bigger. I used a DTRM model.
thanks!