radiation heat transfer in gas turbine burner
 

I try again to expose you a question about case setting in radiation problem. I'm modelling a solid that is exposed to radiation emitted by methane-air flame. The solid domain and the fluid domain are separated by a couple of surfaces (wall and wall-shadow) that have been originated when I have created a "grid interface" (the two domain have been meshed separately). The questions are: 1- Should the two surfaces be "coupled" for the heat transfer? 2- Is the "internal emissivity" of these two surfaces the solid emissivity? 3- Should I set "partecipate in radiation" for the solid? 4- Should I set 0 the "absorption coefficient" for the solid? Thanks and bests regards