Hi everyone,
I am currently trying to simulate a layer of semi-transparent aerogel under sunlight. I try to do it in the physics "radiation in absorbing-scattering media", so that the absorption coefficient of the aerogel on different wavelengths can be taken into account. Now I want to put a solar heat flux (some visible light, some infrared) on its surface, and the only boundary condition that I find relevant is "incident intensity". However the unit of this is W/(m2.sr). I tried turning it into W/m2, by multiplying PI, but the result does not match with my theoretical culculation (I made a simple case of a block). In contrast, if I use "heat flux" in the "heat transfer in solids" physics, the result matches quite well with my theoretical calculation. (In the above attemps, I assumed that the material is transparent in order to varify the COMSOL environment. I set the absorption coefficient etc. to almost zero, so the result should match with my transparent theoretical calculation.)
Could anyone explain what is unique with this "incident intensity"? Can't I use it as a tool for asserting heat flux? If not, what could be a good substitution?
Thank you very much and I am looking forward to a reply.
Best, Megan