Experiment of water vapor adsorption/desorption rate in a desiccant rotor regenerated directly by concentrated artificial solar light irradiation

Abstract

A solid desiccant air-conditioning system has received widespread attention, since it holds obvious predominance such as using low grade solar energy for a regeneration process of desiccant materials. For heating and regenerating a desiccant rotor in the system, indirect methods such as air heating or water heating with solar collectors have been focused in most previous studies. In indirect methods, however, regeneration temperature cannot sufficiently become high due to low thermal efficiency of solar collectors, that is, heat loss. To overcome this problem, an idea of heating and regenerating the desiccant rotor by direct concentrated solar irradiation using a non-imaging Fresnel lens was previously proposed by two of the present authors. The objective of this study is to present experimental results of dehumidifying (adsorption) rate of a desiccant rotor regenerated by direct concentrated irradiation from an artificial solar lamp. The dehumidifying rate was measured in the conditions of different inlet air temperatures, relative humidities and flow velocities, and the influences of these operating parameters on the dehumidifying rate and outlet humidity were examined. The dehumidifying rate increased with the inlet humid air temperature due to high air temperature giving a large vapor pressure difference between the humid air and the air adjoining the desiccant rotor wall surface. The dehumidifying rate also increased almost lineally as the relative humidity increased, as in indirect heating systems. Moreover, the rate showed a maximum at intermediate flow velocity. In the present study, the optimum velocity reaching a maximum seemed around 0.15 m/s.