An analysis of thermal radiation in porous media under local thermal non-equilibrium

The present work investigates the thermal radiation transport inside porous media under local thermal non-equlibrium conditions. Two different geometrical situations, a two-dimensional channel and a cylindrical geometry are considered in the analysis. Porous media application are generally associated with high-temperature combustion and radiative heat transfer is dominant. In this paper, by considering a stream of high-temperature flow in geometries filled with porous medium, the effect of thermal radiation on the solid and fluid phase temperature fields are calculated and analysed. Two radiative heat transfer techniques, the Discrete Ordinate Method (DOM) and the Finite Volume Method (FVM) are tested and the results are compared with a non-radiative model and with a model based Rosseland approximation. A sensitivity study for the variation of absorption and scattering coefficients and the effect on the solid and fluid phase temperature fields is also undertaken. The effect of the extinction coefficient on the Nusselt number is also examined. The temperatures obtained through the Rosseland model shows differences up to +34% and -26% compared to temperatures calculated with the DOM or FVM radiation calculation methods. The temperature fields obtained through DOM and FVM are very similar and some significant differences can only be seen in the cases where a very low number of angular directions are used