Generalized Computations of the Gray Body Shape Factor for Thermal Radiation from a Rectangular U-Channel

Gray body shape factors are computed for radiation exchange between the interior of rectangular fin structures and a nonreflecting ambient. The shape factors are derived from an equivalent thermal circuit using emissivity-dependent resistance elements between each black body potential and corresponding radiosity node. Geometric-shape-factor-dependent resistance elements connect interacting radiosities. Several curves are plotted to aid the heat sink designer to assess the radiative heat transfer for n variety of heat sink dimensions and emissivities. These results show that gross errors exist in some of the previously published data and prediction methods in common usage throughout the electronics industry.