Spray parameter analysis and performance optimization of indirect evaporative cooler considering surface wettability

Abstract

Along with the increasing energy consumption of space cooling, the building industry is in urgent need of the environmental-friendly and proven cooling technology. Indirect evaporative cooling (IEC) is attracting wider attention as a sustainable technology based on the heat absorption properties of evaporation. It has been demonstrated that the plate surface covered by the water membrane in the wet channels has a substantial effect on the operating performance in the practical use of IEC technology, while the ideal state of the uniform water distribution assumed by existing models is usually difficult to be achieved. In order to enhance the evaporation process, it is crucial to tune the nozzle features in water supply session and organize the nozzles suitably over the heat exchanger. In this study, a three-dimensions Computational Fluid Dynamics (CFD) model is therefore proposed, which considers the actual wetting factor of the plate surface. In addition, the movement of the spray droplets as well as the formation and flow state of the water film covering the plate surface, are reflected in the simulation model to predict the performance of the IEC under normal operation more accurately. The results depicted that the maximum coverage area could be achieved when the diameter of the spray droplet maintains 0.25 mm with the flow rate is 5.4 L/min, and the distance between two nozzles is 80 mm. Besides, the maximum value of the wet-bulb efficiency and the coefficient of performance (COP) of the IEC system with optimised nozzle parameter settings could be improved up to 15.1 % and 17.6 % respectively compared to the conventional one. The proposed 3D model could contribute to the improvement of further IEC technique by providing a homogeneity of the water film covered on the plate surface to reflect future research into the heat and mass transfer mechanisms of hydrophilic materials.