蒸发预冷进风闭式冷却塔的冷却性能对比研究

Comparative Study on the Cooling Performance of Evaporative Precooled Air Intake Closed Cooling Tower

闭式冷却塔因其稳定、环保、节水等特点而应用广泛,为了减少机械通风闭式冷却塔塔内喷淋开启的运行时间以节省水损耗,提出了一种直接/间接蒸发预冷进风的闭式冷却塔,利用蒸发预冷进风技术减少塔内喷淋开启的运行时间.采用MATLAB编写了机械通风闭式冷却塔、直接/间接蒸发预冷进风闭式冷却塔的迭代计算程序,仿真研究了3种冷却塔在典型干热地区(新疆哈密)应用时的冷却性能和水损耗.结果表明,塔内喷淋关闭时,当进水温度都为43℃时,在3月、10月、11月,直接蒸发预冷进风的闭式冷却塔的出塔水温比间接蒸发预冷进风的闭式冷却塔和机械通风闭式冷却塔的出塔水温分别低0.46℃和0.96℃、0.42℃和0.93℃以及0.37℃和0.45℃.在3月、10月、11月,相比于间接蒸发预冷进风的闭式冷却塔,直接蒸发预冷进风的闭式冷却塔每单位MW排热率的节水率分别为47.43%、48.66%和44.62%.可见,在直接/间接蒸发预冷系统可以应用的3月、10月和11月,直接/间接蒸发预冷系统都可以提升机械通风闭式塔在塔内喷淋关闭时的冷却效果,但直接蒸发预冷系统的冷却效果和水损耗均比间接蒸发预冷系统好,建议实际应用时采用直接蒸发预冷进风以减少闭式冷却塔的运行水损耗.

Closed cooling towers are widely used because of their stable performance,environmental friendliness,and water-saving features.To reduce the running time of spray-on in a mechanically ventilated closed cooling tower to save water loss,direct and indirect evaporative precooled air intake closed cooling towers were proposed,which utilizing the evaporative precooled air intake technology.Iterative calculation programs for the mechanically ventilated as well as direct and indirect evaporative precooled air intake closed cooling towers were written using MATLAB,and the cooling performance and water loss of the three cooling towers were simulated and studied under typical dry heat regional conditions(e.g.,Hami,Xinjiang).The results showed that when spray systems in all towers were switched off and all inlet water temperatures were at 43℃in the months of March,October,and November,the outlet water temperatures of the closed cooling tower with direct evaporative precooled air intake were 0.46℃and 0.96℃,0.42℃ and 0.93℃,and 0.37℃ and 0.45℃ lower than those of the indirect evaporative precooled airintake and the mechanically ventilated closed cooling towers,respectively. In March,October,and November,thewater saving rate per unit MW of the closed cooling tower with direct evaporative precooled air intake was 47.43%,48.66%,and 44.62%,respectively,compared with the closed cooling tower with indirect evaporative precooled airintake. These results show that during the months of March,October,and November,when the direct and indirectevaporation precooled systems can be applied,these precooling systems can improve the cooling effect of themechanically ventilated closed cooling tower when the spray in the tower is closed. Additionally,the cooling effectand water loss of the direct evaporation precooled system are better than those of the indirect evaporation precooledsystem. Therefore,in practical applications,it is recommended to use the direct evaporation precooled system toreduce the operating water loss of the closed cooling tower.