ABSTRACT
This chapter is concerned with radiation transfer under the condition of radiative equilibrium. The first case to be considered is that of a gray, absorbing, emitting, and scattering medium; it will additionally be assumed that the bounding surfaces are gray and diffuse. A commonly employed approximation in radiative transfer problems involves replacing the exponential integral by an exponential function. The restriction to diffuse surface emission will be retained. It should be noted that, in the absence of a radiation-participating medium, the net heat transfer between plates will be independent of the assumption that the lower surface is either a diffuse or specular reflector. Thus the present physical model is one that isolates the effect of surface reflection characteristics on radiation transfer within the medium. A particularly meaningful approach to the present problem is the exponential kernel approximation. It may be observed that the difference between the specular and the diffuse curves is quite small.
