Experimental Study of an Open-Cycle Solar Collector/Regenerator Using Liquid Desiccant For Air Conditioning

Abstract

Liquid desiccant has been widely used in various solar energy applications, such as air conditioning and food drying. Especially, in the emerging solar desiccant air conditioning system, the regenerator, where the diluted solution is concentrated, plays an important role. Using the open-cycle solar collectors/regenerators (C/R) to concentrate the dilute solution is an effective way to utilize low-grade solar thermal energy to regenerate desiccant solution for air conditioning. The desiccant solution itself is a heat-collecting fluid and the regeneration process could be enhanced in this arrangement. To evaluate its thermal performance, a lab-scale experiment has been conducted using lithium bromide (LiBr) solution. The effects of ambient weather variables (solar radiation, air temperature, relative humidity) and operation conditions (air mass flow rate, solution flow rate, air inlet temperature, solution inlet temperature, and solution concentration) on the solar regeneration parallel flow configurations have been experimentally investigated. To further investigate the heat- and mass-transfer phenomenon inside the solar C/R, the heat- and mass-transfer coefficients are calculated based on the experimental data using multi-dimensional optimization method. Unlike those traditional correlations available in the literature, the effects of inlet conditions of the air and solution on the heat- and mass-transfer coefficients are clearly identified. Applying these correlations to the simulation model of the solar C/R and comparing the predicted values with the experimental values, the accuracy is satisfactory and can be applied to the further investigation for the thermodynamic performance of the solar desiccant air conditioning system.