Experimental Study On Working Performance Of Hybrid Closed Cooling Towers

Cooling towers, a kind of high efficiency but high-water-consumption equipment, are commonly used to eliminate waste heat of systems, like industrial sites and large-scale air-conditioning systems. Because of the proposition about energy conservation, how to improve the efficiency of the cooling tower has been the main concern. And in recent years, water resources arouse increasingly scarce, particularly in northwest region of China. The cooling tower requires large amount of water. Therefore, how to reduce cooling tower’s water consumption is also an increasingly attention. It is worth mentioning that, with the development of cooling tower so far, there are still some technical problems, such as white mist happening in outlet of the closed cooling towers.In order to solve the above several major problems and achieve renovation of the cooling tower, our team specially built a hybrid cooling tower test platform. Compared with the traditional closed cooling towers, hybrid cooling tower adds finned tubes at its top. So both the dry heat and wet heat happen in it, and the problems of water consumption and white mist are effectively alleviated.In this article, different wind velocities and different amounts of spray water are set for the hybrid cooling tower. These two factors how to function on heat transfer performance and air-flow resistance of the hybrid cooling tower are researched. What’s more, different wind velocities and different amounts of spray water are set for a closed cooling tower. The article makes a comparison between the hybrid cooling tower and the closed cooling tower from the aspects of promotion in heat transfer performance, increase in energy consumption and water-saving performance.Analyzed from the experimental data, the hybrid cooling tower is heavily influenced by wind velocity. When wind velocity is set at 3.5 m/s, heat transfer performance of the hybrid cooling tower can achieve the best, and finned tubes contribute 36.8% of the total heat transfer. Although the set of finned tubes will cause the air flow resistance, but the air-flow resistance in this area is less than the wet area resistance. When wind velocity is set at 3.5 m/s, the air flow resistance of finned tubes accounts 29.4% of the total. Compared with the closed cooling tower, when the wind velocity is set greater than 2m/s, the heat transfer performance of the hybrid cooling tower is improved significantly. In the evaluation of the outlet water temperature, the heat transfer performance can be enhanced up to 52%. But with the consideration of energy consumption of cooling water pumps, spray pumps and fans, the total air-flow resistance of the hybrid cooling tower is slightly increased. At last, maintaining the same wind velocity and heat load for the hybrid cooling tower and the closed cooling tower, due to the bear of the finned tubes, the hybrid cooling tower reduces the evaporation of spray water up to 36.8% of the total. So the hybrid cooling tower is a water-saving cooling tower suitable for northwest area of China.