Effect of orientation on the natural convection heat transfer from a heated triangular prism embedded in porous media

Abstract

The natural convection from a heated triangular prism buried in a porous medium packed into a 0.2 m square duct is investigated experimentally. The porous medium comprises glass balls of 3 mm size saturated by air as the working fluid. The 26 mm copper equilateral triangular prism of 0.2 m length is placed at the center of the duct with its base either facing upward or facing downward. The prism is subjected to a constant heat flux with the values of 821, 1038 and 1282 W/m 2 . The results evinced the direct proportionality of the peripheral surface temperature with the heat flux, and the average surface temperature for the base facing down orientation is higher than that for the base facing up orientation. The Nusselt number manifested higher values for the base facing up orientation representing the better heat transfer characteristics due to the smooth air flow along the inclined sides and the eddies formation above the plane face of the triangle. Empirical correlations obtained in this study offer a good agreement with the experimental results that is represented by a deviation of only about ±0.2%.