暖通空调专业 毕业设计外文翻译---冷却塔.doc

Unlike chillers, pumps, and air handlers, the cooling tower must be installed in an open space with careful consideration of factors that might cause recirculation (recapture of a portion of warm and humid exhaust air by the same tower) or restrict air flow. A poor tower siting situation might lead to recirculation, a problem not restricted to wet cooling towers. Similar recirculation can occur with air-cooled condensing equipment as well. With cooling tower recirculation, performance is adversely affected by the increase in entering wet-bulb temperature. The primary causes of recirculation are poor siting of the tower adjacent to structures, inadequate exhaust air velocity, or insufficient separation between the exhaust and intake of the tower.
Multiple tower installations are susceptible to interference — when the exhaust air from one tower is drawn into a tower located downwind. Symptoms similar to the recirculation phenomenon then plague the downwind tower. For recirculation, interference, or physically blocking air-flow to the tower the result is larger approach and range which contribute to higher condensing pressure at the chiller. Both recirculation and interference can be avoided through careful planning and layout.
Another important consideration when siting a cooling tower installation is the effect of fogging, or plume, and carryover. Fogging occurs during cooler weather when moist warm air ejected from the tower comes into contact with the cold ambient air, condenses, and forms fog. Fog from cooling towers can limit visibility and can be an architectural nuisance. Carryover is when small droplets of entrained water in the air stream are not caught by the drift eliminators and are ejected in the exhaust air stream. These droplets then precipitate out from the exhaust air and fall to the ground like a light mist or rain (in extreme cases). Carryover or drift contains minerals and chemicals from the water treatment in the tower and can cau冷却塔不同于冷却器，水泵以及空气处理器，它一定是安装在一个合适的、空旷的空间，并且需要认真考虑可能引起再循环(相同的冷却塔里回收部分暖和的和潮湿的排出气体)或限制空气流程的因素。冷却塔的位置安装不好可能会导致再循环，然而这个问题不适用于那些湿的冷却塔。类似的再循环也同样会发生在用空气冷却的冷凝器中。由于冷却塔的再循环，计入湿球温度计的温度不断的升高，性能也受到了影响。循环的主要因素是不良的线路设置，使塔靠近建筑物，或排气的速度不合适，或者是循环塔的进出口间的间隔不充分。
当从一个循环塔出来的空气被吸到一个位于其顺风口的位置时，若干个这样的循环塔的安装就易于发生冲突。这种迹象类似于再循环的现象，再传递给其余顺风处的循环塔。对于再循环、冲突或者物理上地对循环塔气流的阻断，都会增大冷却器中冷凝压力的波动范围。然而再循环和冲突，只要经过仔细的计划和设计都可以得到避免。
在安装一个冷却塔时要仔细考虑雾的影响，或卷入或转移。雾常出现于较冷的天气里，当潮湿的暖空气接触到从冷却塔里喷射出的冷空气时，经过冷凝后就形成了雾