Radiative transfer over small distances from a heated metal.

Published works have predicted that the radiative transfer from a heated metal to a lossless dielectric a short distance away is many orders of magnitude times the free-space Planck density. It is shown analytically that the radiative transfer from a heated metal to a lossless dielectric of index n(3) is n(3)(2)e(13) times the free-space Planck density, where e(13) is the emissivity of the metal radiating into the lossless dielectric. This radiative transfer is never larger than n(3)(2) (approximately one order of magnitude for semiconductors in the infrared) times the free=space Planck density. The expressions presented show that the maximum radiative transfer from a lossy metallic heat source with a dielectric function of imaginary part ?(I) must be proportional to n(3)(3)/ radical?(I), of which a factor of n(3)(2) arises from the power density within a dielectric and a factor of n(3)/ radical?(I) arises from the emissivity of a metal radiating directly into a dielectric.