EXPERIMENTAL STUDY ON A TWO-STAGE LIQUID DESICCANT DEHUMIDIFICATION SYSTEM USING DUAL DESICCANT SOLUTIONS

摘要

A two-stage liquid desiccant dehumidification system using a lithium chloride (LiCl) solution and a calcium chloride (CaCl2) solution respectively in the first- and second-stage dehumidifier was proposed through numerical analysis and exergy analysis in the previous study and it is improved by two methods, i.e., the high concentration variance and predehumidification of CaCl2. To assess its dehumidification performance and the predehumidification effect of the first-stage dehumidifier using CaCl2, an experimental study is carried out with dehumidifiers of the size 300 mm x 250 mm x 300 mm packed with Celdeck material under three typical conditions, i.e., ARI standard outdoor conditions, ARI dry outdoor conditions, and the typical summer outdoor conditions in Shanghai. It is proved that the humidity ratio of air after two-stage dehumidification under the ARI standard outdoor conditions and ARI dry outdoor conditions meets the requirement of the ARI indoor conditions when the LiCl concentration is in the range of 40-35% and the initial concentration of CaCl2 is 40%. It is founded that the predehumidification of a CaCl2 solution is significant. It can handle 20-63% of the total moisture load in the case studied. A parametric analysis has also been made. The results indicate that the humidity ratio after dehumidification is mainly influenced by the air velocity and the desiccant concentration of Lidl solution. The dehumidification performance deteriorates when the desiccant solution flow rate is around 300-400 kg/h due to the poor distribution of desiccant solutions on the packing material. The moisture removed by the CaCl2 solution depends on its concentration and the air velocity.