Abstract
Mass transfer between solid particles in a packed bed and a flowing fluid in laminar flow region, where both forced and natural convection are important, was analyzed theoretically. The diffusion equation based on the free surface model proposed by Happel was solved and an approximate solution relating the average Sherwood number to the Peclet number, the Rayleigh number and the void fraction of a packed bed was obtained. The published experimental mass transfer data in packed beds were found to agree well with the theoretical predictions.