Heat and Mass Transfer Performance Evaluation and Advanced Liquid Desiccant Air-Conditioning Systems

Abstract

In recent years, liquid desiccant air-conditioning systems have attracted much attention for its prominent potential of energy saving. In such systems, dehumidifiers/regenerators are the core components where heat and mass transfer occurs. The heat and mass transfer coefficients determine the accuracy of mathematical model which were used to design the dehumidifiers/regenerators. So, in this paper, the methods to obtain heat and mass transfer coefficients are evaluated theoretically. In order to enhance the mass transfer process, the internally cooled/heated dehumidifier/regenerator is designed and investigated experimentally and theoretically. Further, several advanced liquid desiccant air-conditioning systems are also introduced. Results show that the proposed equivalent integral mean method has high accuracy in calculating the coupled heat and mass transfer coefficients. Unlike Lewis number which was often assumed as one for describing heat and mass transfer between air and water, the defined Le factor may deviate appreciably from one in the heat and mass transfer process between air and liquid desiccant. The internally heated regenerators help to develop zero-carryover gas–liquid contactors because of much higher performance than adiabatic regenerators under low solution flow rate. It also helps to reduce energy consumption because of the high regeneration thermal efficiency, which indicates that the internally heated regenerators are promising and deserve much more renovation and application.