冷却塔

冷却塔（Cooling tower），火力发电厂、核能发电厂、大型空调设备和制冷设备的循环水冷却装置，冷却水塔又称冷却塔，是一种排热装置，利用将水流冷却到较低的温度，再将系统中的热量排放到空气中，用这样子的方式来降低系统温度到湿球温度附近 之装置，根据其通风方式，可以分为自然通风冷却塔和机力通风冷却塔。大多数发电厂的冷却塔结构都是单叶双曲面形状。由于单叶双曲面是一种双重直纹曲面（Ruled surface），它可以用直的钢梁建造。这样既可减少风的阻力，又可以用最少的材料来维持结构的完整。若以其热传导方式分类，冷却塔大致有 :In a wet cooling tower (or open circuit cooling tower), the warm water can be cooled to a temperature lower than the ambient air dry-bulb temperature, if the air is relatively dry (see dew point and psychrometrics). As ambient air is drawn past a flow of water, a small portion of the water evaporates, and the energy required to evaporate that portion of the water is taken from the remaining mass of water, thus reducing its temperature. Approximately 970 BTU of heat energy is absorbed for each pound of evaporated water (2 MJ/kg). Evaporation results in saturated air conditions, lowering the temperature of the water processed by the tower to a value close to wet-bulb temperature, which is lower than the ambient dry-bulb temperature, the difference determined by the initial humidity of the ambient air.To achieve better performance (more cooling), a medium called fill is used to increase the surface area and the time of contact between the air and water flows. Splash fill consists of material placed to interrupt the water flow causing splashing. Film fill is composed of thin sheets of material (usually PVC) upon which the water flows. Both methods create increased surface area and time of contact between the fluid (water) and the gas (air), to improve heat transfer.把空气流动通过冷却塔的方法大致有三种 :由于有良好的结构强度及可以节省较多建造物料，双曲面结构（Hyperboloid structure）冷却塔所有自然抽风形式冷却塔的标准设计。双曲面亦可以增加向上对流空气的流动速度并增加冷却效率。此种设计的冷却塔亦特别广为不靠近海边或大量水源的核能发电厂及燃煤发电厂所用。而混合型冷却塔的热处理效能则可高达92%。