Performance optimization of a heat pump driven liquid desiccant dehumidification system using exergy analysis

Abstract

Liquid desiccant dehumidification system driven by heat pump is recognized as an efficient approach for humidity control in the air-conditioning system. The liquid desiccant dehumidification system is optimized by exergy destruction analysis method in the present research. According to the exergy destruction theory, the exergy destruction of a liquid desiccant dehumidification system is divided into exergy destructions arising from heat pump cycle, evaporators, condensers, heat and mass transfer modules and various mixing processes, respectively. The heat and mass transfer process uniformity coefficients γt and γω are proposed to describe the uniformity of the heat and mass transfer driving forces along the whole system. It’s indicated γt and γω of the basic cross-flow system are as high as 1.4 and 1.2. Then reducing the exergy destruction is chosen as the guideline to optimize the system. On the basis of the basic cross-flow system, the improved cross-flow system and the improved counter-flow system are further proposed. γt (γω) of the improved systems are reduced to 1.12(1.12) and 1.04(1.01), respectively. Owing to the system optimization, the exergy efficiency increases from 20.1% of the basic cross-flow system to 21% and 25% respectively, COPsys increases from 5.7 to 6.0 and 7.4 respectively. The exergy analysis method is effective for an optimized scenario of a heat-pump driven liquid desiccant process.