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Cooling tower
a construction for cooling water by using air from the atmosphere. Modern cooling towers are used mainly in industrial circulation-based (recycling) water systems to cool the water that extracts heat from heat-exchangers, compressors and so on. Cooling is achieved mainly by partial evaporation; water flowing over the contact surface by force of gravity (1% evaporation) is cooled by about 6°C.
Cooling systems may be divided by type of contact surface into film, splash and spray; or by means of air-supply into fan-assisted, mechanical-draft (in which a flow of air is created by using a tall stack), and natural-draft (or atmospheric), which use wind power and partially natural convection to create a flow of air (see illustration). Fan-assisted cooling systems, in turn, can be divided into sectional and free-standing. Such cooling systems are better and more reliable at cooling water, and allow for greater specific heat loads than mechanical- and natural-draft systems, but require additional electricity.
The capacity of a cooling system is defined by the amount of water cooled per square metre. At the project planning stage, the type and size of the cooling system and its principal elements are determined by technical and economic calculations depending on the quantity and temperature of water to be cooled and the parameters of the atmospheric air.
