Transfer mechanisms governing natural convection in porous media with coupled mass transfer

This paper presents a detailed model of natural convection in horizontal porous media when the surfaces of the packing material are wet and the voids are saturated with vapour and a second non-condensing gas. From the model, system parameters are obtained and the influence of some are determined from an analysis of previously published experimental data. Neglecting geometric parameters, since they were not varied in the experiments, those which affected the Nusselt number were the Rayleigh number based on fluid heat transfer properties, the ratio of temperature to concentration driven buoyancies, and the ratio of the potential for latent relative to sensible heat transfer. Since the Prandtl and Lewis numbers which relate to heat and mass transfer between fluid and solid were not significant, it appears that the influence of these effects is much less pronounced than in the case of heat transfer alone in a similar system. While this is attributed in part to the manner in which the experiments were performed, it is also to be expected when mass transfer forms a large component of the total heat transfer.