  The theory of heat transfer by electromagnetic radiation is based on the
radiative transfer equation (RTE) for the radiation intensity, or equivalently
on the Boltzmann transport equation (BTE) for the photon distribution. We focus
in this review article, after a brief overview on different solution methods,
on a recently introduced approach based on truncated moment expansion. Due to
the linearity of the underlying BTE, the appropriate closure of the system of
moment equations is entropy production rate minimization. This closure provides
a distribution function and the associated effective transport coefficients,
like mean absorption coefficients and the Eddington factor, for an arbitrary
number of moments. The moment approach is finally illustrated with an
application of the two-moment equations to an electrical arc.
