at a surface can be determined by finding the difference between the incoming and outgoing energy: Using the equation for radiosity Je,i = εiσTi4 + (1 − εi)Ee,i, the irradiance can be eliminated from the above to obtain where Me,i° is the radiant exitance of a black body.

For an enclosure consisting of only a few surfaces, it is often easier to represent the system with an analogous circuit rather than solve the set of linear radiosity equations.

The heat transfer is found by using the appropriate potential difference and equivalent resistances, similar to the process used in analyzing electrical circuits.

In such a case, the radiosity does not depend on the angle of incidence of reflecting radiation and this information is lost on a diffuse surface.

So, the heat transfer between two surfaces relies on both the view factor and the angle of reflected radiation.

It was also assumed that the surface is a gray body, that is to say its emissivity is independent of radiation frequency or wavelength.

However, this problem is solved by simply subdividing the surface into smaller elements until the desired accuracy is obtained.