Coupled heat and mass transfer by natural convection from vertical surfaces in porous media

Similarity solutions for buoyancy induced heat and mass transfer from a vertical plate embedded in a saturated porous medium are reported for (1) constant wall temperature and concentration, (2) constant wall heat and mass flux. In addition, the effect of flow injection on the heat and mass transfer has also been considered. Governing parameters for the problem under study are the buoyancy ratio, N, and Lewis number, Le. Depending on the sign of the buoyancy ratio, inclusion of a concentration gradient may either assist or suppress the flow induced by thermal buoyancy. The Lewis number is found to have a more pronounced effect on the concentration field than it does on the flow and temperature fields. Results for Nusselt and Sherwood numbers cover a wide range of the governing parameters, -1 < N < 10 and 0.1 ≤ Le ≤ 100, and a comparison is made with the results of Bejan and Khair (Int. J. Heat Mass Transfer 28, 909-918 (1985)).