Use of Indirect Evaporative Cooling as Pre-cooling Unit in Humid Tropical Climate: An Energy Saving Technique

Abstract

Evaporative cooling system is an environmentally-friendly and energy saving technology for air conditioning. However, in hot and humid climates, it is rather inefficient due to the high wet bulb temperature of the ambient air. In order to take advantage of indirect evaporative cooling (IEC) system in humid tropical climates, we present a hybrid system that combines IEC system and vapor compression system. In the IEC unit, the exhaust air from the conditioned room is used as the working air, and outdoor fresh air is used as the product air so that the IEC unit produces pre-cooled air for vapor compression system. In this study, two types of IEC units, namely, a conventional counter flow IEC unit and a novel counter flow IEC unit based on M-cycle, have been numerically analyzed. Results have indicated that the humid outdoor fresh air can be pre-cooled to a temperature below its dew point temperature when the wet bulb temperature of the exhaust air is lower than the dew point temperature of the outdoor air. In addition, the use of IEC reduces the cooling load of the vapor compression system, as a result, the hybrid system has a large potential to reduce electricity demand and energy consumption.