TWO-PHASE FLOW OF ADSORBED VAPORS

Abstract

Through a microporous medium, transport of a vapor may occur in an adsorbed film and in the gas phase. The formulation of this two-phase transport has been given in terms of forces and associated phenomenological coefficients, and the resultant expression for the total flux has then been related to the complex Darcy law and Fick law coefficients of flow and diffusion respectively. It is suggested how the various coefficients may be determined as functions of gas pressure or surface concentration of sorbate. The diffusive and hydrodynamic models of transport are considered as two limiting cases of the transport phenomenon, the former of increasing importance for decreasing sorption below monolayer coverage and the latter dominant above monolayer coverage. Steady state total concentration gradients are considered in presence and absence of blockage of gas phase flow by capillary condensate and multilayers, and when there is and is not interconversion between surface and gas phase fluxes along the direction of flow. Finally, the fluxes of each component in a two-phase two-component flow are derived. This problem is of major importance in the separation of mixtures by flow through microporous barriers.