Experimental investigation on a novel spray-medium pad coupled two-stage evaporative cooling system to enhance heat and moisture transfer performance

Lowering the air temperature using evaporative cooling technology is an effective way to enhance the performance of an air-cooled chiller system and hence achieve electric savings. Application of the spray cooling and the wet medium is limited because of low cooling efficiency and high water consumption, respectively. A novel two-stage evaporative cooling system (SMEC), with the coupling of spray and medium pad, has been proposed to overcome these limitations. An experimental platform was set up to test cooling and humidification performance, analyzing the effects of inlet air relative humidity, velocity, and spray flow rate. At 35 °C and 50 % humidity, SMEC can reduce temperature by 7.4 °C with 81.3 % evaporative cooling efficiency. The cooling efficiency is improved by more than 8.3 % compared to a single medium pad and 11.6 % compared to a single spray by SMEC. Higher efficiency is achievable with a thinner medium pad and less water usage. Additionally, the cooling and humidification performance of the SMEC is found to decrease with increasing inlet air relative humidity and velocity, while it is observed to increase with increasing spray flow rate. The cooling capacity and coefficient of performance (COP) are found to decrease with increasing inlet relative humidity and to increase with increasing inlet air velocity. The cooling capacity is observed to increase with increasing spray flow rate. Compared with a single medium cooling system, the COP of the SMEC system increased by 10.7 %.