Combined Conductive and Radiative Heat Transfer in an Optically Thick Porous Body : Case of Cordierite Porous Bodies

The Chebyshev polynomial expansion of the source function is presented to analyze the combined conductive and radiative heat transfer in an optically thick porous body. Better agreement between the theory and the experiment is shown concerning the temperature profiles and the heat transfer characteristics of cordierite porous bodies. This analytical method is also applied to the examination of the Rosseland approximation to radiative transfer in an isotropically scattering medium, and consequently it is revealed that the Rosseland approximation is valid in the range of optical thicknesses greater than 200. Moreover, it is suggested that in the case of ceramic porous bodies possessing a three-dimensional netted structure an increase in the equivalent extinction coefficient and a decrease in the tortousity-discontinuity factor are much conducive to improvement of their thermal performance as thermal insulators.