Distributed parameter simulation of annular-finned tube sorption bed

Abstract

A distributed-parameter model of a sorption bed heat and mass exchanger is presented. The model includes energy and mass balances for the heat transfer fluid, tube, annular fins, and adsorbent. The conservation equations are discretized and solved to determine the temperature and uptake profiles for a silica gel-water sorption bed during the isosteric heating and desorption stages of an adsorption heat pump cycle driven by 90°C water. The results show that during the beginning of the heating stage, there are substantial temperature differences (16.5 K over 3 mm) along the radial and axial directions. This temperature gradient translates to a difference in uptake of ~10% across an individual adsorbent cell. The effect of the contact heat transfer coefficient between the adsorbent and tube is also quantified. Significant but achievable improvements in contact heat transfer yield appreciable reductions in sorption bed cycle time.