Thermal analysis on natural convection coupled with radiative heat transfer in a saturated porous cavity

Abstract

Porous foam is an ideal material for enhancing radiative heat transfer in numerous thermal equipment. The solid skeletons of porous foams can absorb/ release radiative energy and transfer convective energy with the surrounding fluid in the pores. In this paper, the conduction-convection-radiation coupling heat transfer in a porous cavity is investigated. A local thermal nonequilibrium model is used to represent the energy transport during the solid and fluid phases. The heat flux caused by thermal radiation is obtained by solving the radiation transfer equation. The thermal and fluid fields are studied to discern various parameters, including the Planck numbers Pl , the modified Rayleigh numbers Ra , and the interphase heat transfer coefficients H . Our study indicates the following: (1) the effect of radiation can be neglected when Pl > 20; (2) the modified Rayleigh numbers have little influence on the solid temperature when the radiative heat transfer is dominant and the convective heat transfer between the two phases is weak; and (3) the local thermal-equilibrium can be formed when H exhibits high values.