Analysis of heat transfer characteristics of an unsaturated soil bed: a simplified numerical method

Abstract

This paper is a continuation of a study reported in this Journal in February 1999. The paper presents a summary of the two-dimensional macroscopic continuity, momentum and energy equations in a cylindrical co-ordinate system that describe heat and mass transfer through unsaturated soil. The hydrodynamic laws governing flow of water through unsaturated soil are also presented. The explicit numerical procedure and the method to solve the equations are described. Characteristics of the corresponding computer program are also discussed. The results obtained with the current cylindrical governing equations are compared with the previously reported results based upon the Cartesian system of equations. It is observed that the results obtained with cylindrical formulations are in closer agreement with the experimental results. The effects of various heat transfer processes as well as the motion of fluids on heat transfer in a clay bed coupled to a heat pump are discussed. Heat diffusion into the soil by conduction is shown to be predominant through the early stage of heating, while the liquid water motion contributes to heat transfer during the intermediate times and the gas motion is shown to become significant during the last stages of drying. The contribution of the convective transport increases with the temperature and becomes equal to the contribution by conduction at moderately high temperatures. Copyright © 2001 John Wiley & Sons, Ltd.