Experimental study on exhaust internal circulation desiccant wheel evaporative cooling chiller

Evaporative cooling chillers reduce the water temperature by absorbing heat during the evaporation of water without the need for compressor assistance or refrigerants. It is an energy-saving and environmentally friendly cooling technology but it needs necessary improvements in the applicable environmental area and refrigeration performance due to ambient air wet-bulb temperature limitations. To obtain chilled water below the dew-point temperature of the ambient air, an exhaust internal circulation desiccant wheel evaporative cooling chiller is proposed and experimentally investigated. A combination of a heat pipe exchanger, a desiccant wheel, an air cooler and an air heater are applied to reduce the wet-bulb temperature of the ambient air before it passes through the direct evaporative cooler. At the same time, the low-temperature and low-humidity exhaust air from the direct evaporative cooler is used to circulate to improve chiller performance. The experimental results show that the average chilled water temperature of the proposed chiller is 10.2 ℃ lower than that of the direct evaporative cooling chiller under five typical environmental conditions. The wet-bulb efficiency of the proposed chiller is the highest at high temperatures and high humidities (36 ℃ and 80% RH), which is 6 times greater than that of direct evaporative cooling chillers. Therefore, the proposed chiller expands the application range of evaporative cooling technology, which is especially suitable for humid areas with low-grade heat utilization such as solar energy.