Radiative-conductive heat transfer in a spherical cavity

A mathematical model describing joint radiative-conductive heat transfer in a spherical cavity, the shape of which can be considered as a statistical average in relation to the forms of closed pores in solids, is developed. The model determines an equivalent thermal conductivity of an arbitrary diathermic medium in a cavity that allows a material with a porous structure to be considered as a continuous inhomogeneous solid. The effect of the temperature field gradient in the vicinity of the cavity and the thermal conductivity of the diathermic medium on the equivalent coefficient of thermal conductivity is determined. In the case of a thermally nonconducting medium, the calculated dependence of this coefficient is compared to equations, similar in structure, derived on the basis of different approaches to account for heat transfer by radiation in pores.