improve document, equation in CatUtil (radtrn)

[aymhenry]

Improve documentation, for CatUtil.
Function radtrn

• need a new name, to show its function.
• the Fortran function returns two values, i think one is onl one.

[oabdelaziz]

where is radtrn used? from what I can read, this function calculates the heat flux due to radiation heat transfer to the ambient

[aymhenry]

where is radtrn used? from what I can read, this function calculates the heat flux due to radiation heat transfer to the ambient

• Function (radtrn) is listed in CatUtil file, this function is used by Qlxxx files (Ql2, Ql13,Ql456,and Ql8). not found in Ql5

we may change name to (getHeatFlux). but confirmation is required, it has to return Q (heat) value only.

[oabdelaziz]

a more informative name would be getRadHeatFlux