Improving Building’s Thermal Performance by Means of Porous Media–An Experimental Free Convection Work

Abstract

The thermal efficiency of the modified Trombe-wall system proposed in this work is improved compared to its conventional version thanks to the adjunction of a porous material to the absorber wall. Thermal measurements were made in a wide Rayleigh number range, with high values reaching 4.52 x 10(9). The ratio between the matrix's thermal conductivity of the porous material and that of the air varies between 1 (without porous medium, conventional Trombe-wall system) and about 1888. Moreover, the aspect ratio of the active cavity varies in the 0.1-0.3 range. Influence of these physical parameters on the free convective heat transfer occurring in the active cavity are quantified for this new assembly and compared to the conventional one. The results show that the average convective heat transfer systematically increases with the ratio of thermal conductivities for any Rayleigh number and cavity's aspect ratio. Furthermore, the simple modification makes it possible to increase the overall thermal efficiency between 4% and 23% on average. This work complements and confirms the numerical results of recent studies realized by means of the control volume method.