ABSTRACT
Analyses of mass transfer processes in porous bodies, except the case of non-volatile liquids, should take into account vapor transfer. Different mechanisms of vapor and gas transfer will be considered in this chapter. Free-molecular, viscous and transient regimes are characteristic of one-component vapor and gas flow in porous bodies. A vapor flow obeys different physical laws depending on vapor pressure, the presence of other vapors or gases and pore width. A rigorous verification of the influence of non-uniform electric field on vapor diffusion was obtained through observations of the rate of water evaporation from the capillaries of rather large radii r = 10–20 µm, for which surface diffusion can be neglected. Application of a vapor concentration gradient generates a counter-diffusion of gas that will change the method of calculation of the mass transfer processes. The correction for diffusion slippage of a vapor–gas mixture results in insignificant changes in the quantitative estimated values.
