Comprehensive coupling model of counter-flow wet cooling tower and its thermal performance analysis

Counter-flow wet cooling towers are equipment for removing heat from water to environment. The traditional model for their thermal performance mainly focuses on the heat exchange in packing. The coupling among spray zone, rain zone, and packing are not considered. In this study, a coupling model consisting of mathematical descriptions of the spray zone, rain zone, and packing is proposed. The thermal performance is investigated based on the interaction of three zones. An actual cooling tower test report is used to validate the coupling model. Subsequently, the efficiency and exit water temperature of the cooling tower is analyzed under various conditions. The results indicate that the relative error is 5.68 % when the coupling relation is neglected. The relative error is reduced to 3.25 % when the spray zone and rain zone are coupled with packing. The cooling tower efficiency and exit water temperature increase with increasing air humidity, while the smaller droplets diameter and higher air-to-water mass flow rate ratio cause lower exit water temperature and higher cooling tower efficiency. Besides, the droplets velocity has little influence on these. The results of this study provide theoretical foundations for accurate performance prediction and guide the direction for cooling towers optimization.