[gmori]

Hello everyone.First time asking a question.
I am currently studying the ViewFactor method, one of OpenFOAM's radiation models.

In the ViewFactor method, I am solving the equation below:.
View factor radiation model. The system solved is: C q = b
where:
Cij = deltaij/Ej - (1/Ej - 1)Fij
q = heat flux
b = A eb - Ho
and:
eb = sigma*T^4
Ej = emissivity
Aij = deltaij - Fij
Fij = view factor matrix

1 However, I am not sure how this equation is derived. What is the process by which this formula was derived? Am I correct in assuming that q is the net heat flux emitted at a given surface?

2 In the ViewFactor method, in addition to the variable q, there is another variable qr. I do not know the difference between q and qr.

I know this is a poor question, but I would appreciate if someone could enlighten me!

Source code is attached.
viewFactor.C

viewFactor.H