Analytical and Experimental Study of Combined Conductive and Radiative Heat Transfer Through a Layer of Glass Beads

Abstract

Combined conductive and radiative heat transfer through a layer of glass beads was studied experimentally and theoretically. The temperature profiles and the mean effective thermal conductivities of two soda-lime-silica glass bead layers with different layer thickness were measured for various hot boundary temperatures between 410 to 680 K. The energy equation and the equation of transfer governing the coupled conduction and radiation heat transfer through the layer were solved numerically under the conditions corresponding to the experiment. The effective thermal conductivity by conduction alone and radiative properties of the glass bead layer were evaluated based on Bruggeman's theory and Mie's theory, respectively. Furthermore, porosity distribution within the layer was assumed to be constant. As a result, excellent agreement between theory and experiment was found, and it was concluded that the present analytical method could be used effectively for predicting the temperature profiles and the heat-transfer characteristics of a glass bead layer with comparatively larger bead diameter and layer thickness.