In this article, numerical study of combined natural convection and radiation heat loss from a modified cavity receiver of a solar dish collector using asymptotic computational fluid dynamics approach is presented. The natural convection and radiation heat losses are estimated for different angle of inclinations ranging from 0 degrees (aperture facing sideways) to 90 degrees (aperture facing downward). The numerical results are presented to show the effect of parameters such as Grashof number, angle of inclination, emissivity, temperature ratio, and diameter ratio on convection and radiation heat losses. Separate Nusselt number correlations for natural convection heat loss and combined convective and radiative heat loss are given using the method of asymptotic expansions. The heat loss model is comparable with well-known models. It is observed that the present heat loss model follows the same trend as that of the other heat loss models.