COMPOSITE HEAT-TRANSFER IN A VARIABLE POROSITY MEDIUM BOUNDED BY AN INFINITE FLAT-PLATE

Heat transfer by simultaneous radiation and convection in a variable p orosity medium bounded by an infinite flat plate is determined by solv ing momentum and energy equations. The problem is investigated for two different cases, viz., presence of porous medium and absence of porou s 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 conne cting porosity and permeability is incorporated in the analysis for un ified treatment. A parameter survey is made to study the effect of opt ical thickness, porous parameter, albedo scattering and ratio of condu ction to radiation using Runge-Kutta-Gill method. The heating and cool ing cases are considered for variable porosity situation. The results show that both convective and radiative components decrease with incre ase in porous parameter, and the inhomogeneity of the medium enhances heat transfer rate. The increase in optical thickness leads to decreas e in both convective and radiative fluxes. For a particular value of w all emissivity (epsilon(W) = 0.5932116) the radiative flux is reduced to zero.