Comparison of Dehumidification Performance of Counter and Cross-flow type Liquid desiccant Dehumidifiers

Abstract

In HVAC systems, liquid desiccant systems have attracted research attention in recent years due to their high efficiency in removing latent loads from conditioned buildings while consuming little energy. This paper experimentally investigates the dehumidification performance of the counter-flow type and cross-flow type liquid desiccant system under the same system operation conditions. In this study, Lithium chloride aqueous solution was used as the desiccant solution and CELdek-structured packing was selected. Dehumidification efficiency and moisture-removal rate were adopted as dehumidification performance indices. To investigate the impact of air and solution conditions on the two indices, five parameters—liquid-to-gas ratio, inlet-air temperature and humidity ratios, solution temperature, and concentration—were measured. Experiments were performed inside a test chamber, and the test chamber provided the same summer operation conditions. An 8.1 l/min constant-flow pump was adopted, and mass flow rate of the process air was subsequently determined based on the operation ranges of the liquid-to-gas ratio. Effects of air- and liquid-flow directions on the dehumidification process under various operating conditions were analyzed. Dehumidification efficiency of the counter-flow- and cross-flow-type dehumidifiers varied over the ranges 54.6–78.2% and 50.6%–74.4%, respectively. Similarly, moisture removal rates of the two dehumidifiers varied over ranges 0.39–0.76g/s and 0.36–0.73g/s, respectively. These results indicate that dehumidification performance of both dehumidifiers decreases with increase in inlet-solution temperature. In addition, deviations in dehumidification efficiency and moisture removal rate within 10%, which indicates that there is no significant difference in dehumidification performance between the counter-flow and cross-flow dehumidifiers with increase in inlet-solution temperature.