Quick performance prediction of liquid desiccant regeneration in a packed bed

The major energy requirement associated with any liquid desiccant-based systems is the low-grade energy for desiccant regeneration. This paper presents the results from a simplified model of a packed bed regeneration process in which the desiccant solution is heated in any of the two ways. With method A, the desiccant solution is heated in a heat exchanger with a fluid (water) heated by any low-grade thermal energy such as solar energy or waste heat sources. While in method B, the desiccant solution is heated by a conventional energy source such as a line heater. A closed form solution is obtained for both methods of heating through two dimensionless performance parameters to estimate the water evaporation rate from the weak desiccant solution to the scavenging air stream in terms of known operating parameters. Good agreement is shown to exist between the predictions from the simplified model and the experimental findings available in the literature. The influences of the heating fluid (water) inlet temperature and the effectiveness of the heating fluid-to-desiccant heat exchanger on the performance of the regenerator are studied for method A whereas the effects of energy input on the evaporation rate of water with the scavenging air flow rate are investigated for method B and the results are reported in this paper. (c) 2004 Elsevier Ltd. All rights reserved.