Scaling analysis of heat and mass transfer processes in an adsorption packed bed

Abstract

In this article, a scaling analysis of heat and mass transfer processes in an adsorption packed bed is presented. New scaling parameters that characterize the performance of the adsorption cooling bed are derived and their importance are discussed. In addition, a numerical study is performed to illustrate the roles played by the newly derived scaling parameters. It is found that the presence of heat of adsorption makes the apparent heat capacity of an adsorption bed much larger than the heat capacity of the adsorbent material itself. The present results indicate that the heat diffusion and vapor penetration depths can be used to specify the desired working pair properties and the adsorbent layer thickness for producing the maximum cooling power. From the results of scaling analysis, it can be concluded that the inter-particle permeation resistance has a considerable effect on the performance of an adsorption silica gel bed when the particle diameter to adsorbent layer thickness ratio is less than 0.1. It can also be concluded that performance of a silica gel packed bed is controlled by the conductive thermal resistance when the Fourier number of the adsorbent-adsorbate layer (Fo) is less than 1.0. The convective resistance (i.e., external resistance) dominates the bed performance when the dimensionless temperature ratio (Θ) of adsorption silica gel packed bed is more than 0.2.