基于填料蒸发预冷原理的自然通风干式冷却塔夏天运行效率的优化

PERFORMANCE OPTIMIZATION OF NATURAL DRAFT DRY COOLING TOWER USING WETTED-MEDIUM EVAPORATIVE PRE-COOLING

针对自然通风干式冷却塔夏天运行效率低的问题,提出填料蒸发预冷塔的入口空气的优化措施。填料蒸发预冷一方面引入预冷,可以起到改善干式冷却塔夏天热交换的作用。另一方面,填料也引入了额外的压损,从而减小流经空冷散热器的空气流量,继而会阻碍冷却塔的热交换。对于填料蒸发预冷自然通风冷却塔,存在蒸发预冷所带来的益处与额外压损引入的弊端的权衡,此权衡与蒸发冷却用的填料密切相关。为此,该文分别对2种代表性填料(薄膜式和点滴薄膜式)蒸发预冷的自然通风干式冷却塔进行模拟研究。模拟发现,就蒸发预冷与额外压损的权衡而言,薄膜式填料的性能优于点滴薄膜式填料。该文模拟的120 m高的冷却塔,在高温低湿条件下,经蒸发预冷后的换热效果最高可提升104%。

To offset the low performance of a Natural Draft Dry Cooling Tower（NDDCT）especially on hot days,thepresent study proposes to pre-cool the inlet air of the tower using wetted-medium evaporative cooling. In such case,theinlet air temperature of the cooling tower is reduced which benefits the heat rejection of the tower,however,the extrapressure drop of the wetted media reduces the air mass flow rate passing through the tower and therefore impairs the towerheat rejection. There is a trade-off between evaporative pre-cooling and the extra pressure drop. Literature review findsthat the trade-off is determined by the wetted media themselves. Consequently,the present study simulates theevaporative pre-cooled NDDCTs with two typical wetted media（film and trickle media）. The simulation finds that thefilm medium is superior to the trickle medium in terms of the trade-off between evaporative pre-cooling and the extrapressure drop. At hot and dry conditions,the performance of the 120 m high NDDCT can be improved up to 104%through wetted-medium evaporative pre-cooling.