CHAPTER 7 - HEAT AND MASS TRANSFER IN WALLS

Abstract

This chapter discusses the heat and mass transfer in walls. Walls are very complicated systems consisting of various building materials containing pores, voids, and cracks of various shapes. Transfer of heat and mass takes place in these walls in different ways, and an exact analytical description of the transfer processes presents great difficulties. The basic empirical relationships of heat and mass transfer in capillary-porous bodies are fully appropriate to those systems to which walls pertain. The chapter also discusses heat and mass transfer in homogeneous and multilayer walls, and heat transfer in walls with periodic variations in the temperature of the medium and in the presence of filtration of air. To realize the suggested method of calculation, it is necessary to know the value of the coefficients of heat and mass transfer of the materials from which the wall is constructed. At the present time, experimental data on the basic thermophysical characteristics of building materials are being accumulated and calculations can be made to a first approximation with considerable simplification of the mechanism of heat and mass transfer.