# SimScale CAE Forum

#1

"In Radiation, the hotter body loses heat, and the colder body receives heat by means of a process occurring in some intervening medium which does not itself become thereby hot." - James Clerk Maxwell ^1

In general, Heat Transfer is a process where thermal energy is transferred due to a temperature difference.
The three modes of heat transfer are: Conduction, Convection, and Radiation.

Radiation from a simulation perspective requires a reference temperature (sink temperature) and the emissivity \epsilon.
The radiation heat flux is then calculated with the temperature \tau at the boundary and the Stefan Bolzman constant \sigma:

q=\epsilon\sigma\left(T^4-T^4_{sink}\right)