Study of the immersed depth on the natural convection heat transfer from a heated triangular prism embedded in porous media

Abstract

Estimating the heat loss encountered in many situations with a hot surface buried in a permeable material greatly contributes to the energy conservation and cost analysis of numerous engineering systems. An experimental study was conducted on the natural convection heat transfer from a triangular prism positioned in a 0.2 m2 test section filled by 3 mm glass spheres as a porous material. The air is the working fluid used in the study with the Darcy-Raleigh number (0.1224≤ Ra* ≤ 0.2712). The triangular prism heater (having face side (c) = 0.026 m and L = 0.2 m) is made of copper that is heated electrically and immersed in the porous material at three different depth to radius ratios (h/R=3.5, 10, and 16.5). The results manifested that the peripheral surface temperature around the triangular prism rises with a rise in the h/R ratio and an increase in the heat flux. The mean Nusselt number is proportional to the heat flux and Darcy-Raleigh number. Empirical correlations were obtained from the experimental results, and the differences between measured and estimated values never exceeded ∓ 2.7.