CHAPTER 6 – HEAT AND MASS TRANSFER IN CAPILLARY-POROUS BODIES

Publisher Summary This chapter discusses the heat and mass transfer in capillary-porous bodies. Transfer of noncondensable gases, vapors, and liquids can occur in capillary-porous bodies. Transfer of vapor and inert gas can take place by different methods: by molecular means in the form of diffusion, by molar means, by a filtration motion of the whole steam-gas mixture within the porous body under the influence of a fall in aggregate pressure. Similarly, liquid transfer can take place by means of diffusion, capillary absorption, and filtration motion in the porous medium arising from the hydrostatic pressure gradient. Therefore, the derivation of the rules of mass transfer in a system of capillary-porous bodies on the basis of molecular and molar transfer mechanisms presents great difficulties. These rules can serve for the analysis of the qualitative picture of mass transfer in capillary-porous bodies and can also reveal the nature of the variation of transfer coefficients in relation to the moisture content and temperature of the body. Quantitative calculations, in a majority of cases, are carried out on the basis of thermal properties determined by experimental methods directly for specific bodies. The chapter also discusses the system of differential equations for mass and heat transfer in capillary-porous bodies.