How would you simulate that a surface is radiating to the sky? Say 3K space? Is setting the emissivity of an external surface to 0.9 automatically assuming that this surface is radiating to 0K space? Would I instead put in a large plate and have this set to 3K temperature? If so, how do I set its absorptivity to 1?
The absorptivity is equal to the emissivity in the set up of steady-state simulations (due to Kirchhoff’s Law). So the absorptivity is equal to whatever emissivity you define in the boundary condition or material tab.
