Abstract

Heat transfer by simultaneous radiation and convection in a variable porosity medium bounded by an infinite flat plate is determined by solving momentum and energy equations. The problem is investigated for two different cases, viz., presence of porous medium and absence of porous medium. In the presence of porous medium both variable and constant porosity situations are studied. Similarity solutions are obtained for an isothermal and impermeable wall. The Kozeny-Blake expression connecting porosity and permeability is incorporated in the analysis for unified treatment. A parameter survey is made to study the effect of optical thickness, porous parameter, albedo scattering and ratio of conduction to radiation using Runge-Kutta-Gill method. The heating and cooling cases are considered for variable porosity situation. The results show that both convective and radiative components decrease with increase in porous parameter, and the inhomogeneity of the medium enhances heat transfer rate. The increase in optical thickness leads to decrease in both convective and radiative fluxes. For a particular value of wall emissivity (e w =0.5932116) the radiative flux is reduced to zero.

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