Experimental verification of the effect of air pre-cooling in dew point evaporative cooler on the performance of a solid desiccant dehumidifier

Abstract

One of the research gaps regarding sorption systems to be used in air conditioning, is to increase their efficiency measured by the coefficient of performance (COP). This paper verifies experimentally the way to increase desiccant system performance, through the air pre-cooling in dew point evaporative cooler (DPIEC), before its dehumidification in a rotor desiccant. Experimental tests were carried out in a system consisting of a dew point evaporative cooler, a desiccant rotor, a heat source, and auxiliary equipment enabling the system to operate. The air humidity ratio decrease was determined during the summer by analyzing two operation configurations, both for Polish climatic conditions. In the first Configuration I, the outdoor air is dehumidified in the desiccant rotor, while in the second Configuration II, the outdoor air is pre-cooled in the dew point evaporative cooler before being directed to the rotor desiccant. Tests showed that the system operating Configuration II allows to obtain higher air dehumidification (from 1.4 times to 1.9 times depending on outdoor and regenerative air parameters). To establish system COP the results were supplemented with numerical calculations. It was found that the proposed pre-cooling allows to lower regeneration temperature to achieve the same dehumidification rate the regeneration temperature is decreased by 15°C. Consequently, the use of air pre-cooling as part of sorption air-conditioning system makes it possible to increase its energy efficiency.