Experimental investigation of flow assisted mixed convection in high porosity foams in vertical channels

This paper reports the results of an experimental study on flow assisted mixed convection in a vertical channel containing aluminium metal foams having different number of pores per inch, with high porosity in the range of 0.9 to 0.95. With a view to delineate the flow regimes, experiments are conducted for a wide range of Richardson numbers 0.005 ⩽ Ri ⩽ 1032. Based on a parametric study with a large number of experimental data, a correlation for the wall Nusselt number in the presence of the porous medium as a function of Richardson number, Reynolds number, and the porosity is developed. The novelty of the present work is the use of a wide range of Richardson and Reynolds numbers covering the forced convection dominant and mixed convection regimes. In order to quantify the enhancement of the heat transfer rate in the presence of porous medium, correlations for (i) Nusselt number for a channel without foam, under mixed convection and (ii) ratio of heat transfer rate with and without porous medium have also been developed. The enhancement ratio is always more than one, which clearly indicates that metal foams invariably enhance heat transfer. However, there is a penalty in terms of increased pressure drop.