Applicability of indirect evaporative cooler for energy recovery in hot and humid areas : comparison with heat recovery wheel

Abstract

The indirect evaporative cooler (IEC), used as a novel energy recovery component for central air-conditioning (AC) systems, can cool and dehumidify the fresh air by capturing the waste thermal energy of exhaust air. To facilitate its implementation in hot and humid areas, the applicability of the hybrid AC system integrated with IEC needs to be addressed. This study quantitatively evaluated the cooling and energy-saving potentials of an IEC for energy recovery and compared it to a traditional hybrid AC system with a heat recovery wheel (HRW). On-site performance measurements were conducted in a wet market located in Hong Kong, where two air-handling units were integrated with a newly-designed IEC prototype and a commercial HRW respectively. Simulation models of the two hybrid AC systems were established based on TRNSYS platform by incorporating the numerical model of IEC and HRW respectively. The field-measurement data was used to validate the component models, and further calibrate the system models. To compare the regional adaptability of the two systems, annual simulations were conducted among 8 selected cities in southern China. Results showed that the total cooling capacities of IEC and HRW are closely related to local ambient relative humidity. Compared with the baseline AC system, the AC + IEC provides an annual energy saving intensity of 64.2–73.4 MJ/m2 for cities with hot and moderate humid climates, which is more competitive than the AC + HRW (45.5–51.8 MJ/m2). The annual energy saving ratios of the two types of hybrid systems range from 14.4% to 26.4%.