Influences of radiative characteristics on free convection in a saturated porous cavity under thermal non-equilibrium condition

Abstract

The present work numerically examines the effect of thermal radiation from the solid phase on the thermal and flow field inside a porous medium by investigating free convection within a saturated porous cavity. A local thermal non-equilibrium (LTNE) model is used to represent the energy transport for the solid and fluid phases. The heat flux caused by the thermal radiation is obtained by solving the radiation transfer equation (RTE), so the detailed influence of the radiative characteristics can be analyzed. All the dimensionless governing equations together with the corresponding boundary conditions are solved numerically by Chebyshev collocation spectral method. The results are reported in terms of streamlines, isotherms and average Nusselt numbers for different radiative characteristics such as the conduction-radiation interaction parameter (Pl), the optical thickness (τL), the scattering albedo (ω), and the emissivity of the walls (εW). It is found that the thermal radiation plays an important role on the fluid flow and heat transfer for the buoyancy dominated flow. Substantial changes occur in heat transfer and flow field when Pl, τL, ω and εW vary in the specified ranges. The overall heat transfer is increased with decreasing of Pl and τL, as well as the increasing of εW, however, they are not very sensitive to the change of ω.