A Cooling Tower also commonly known as an evaporative heat rejection equipment is a specialized heat exchanger in which air and water are brought into direct contact with each other in order to reduce the water's temperature. As this occurs, a small volume of water is evaporated, reducing the temperature of the water being circulated through the tower. A factory packaged cooling tower is classified as a unit that is of series production from a manufactures factory (shipped complete or knocked down shipped for ease of transportation). Knocked down shipped products shall be installed by skilled personnel trained / supervised by the certified company. Field erected cooling towers are deemed outside this scope.
Water, which has been heated by an industrial process or in an air-conditioning condenser (Water -cooled chiller), is pumped to the cooling tower through pipes. The water sprays through nozzles onto banks of material called "fill," which slows the flow of water through the cooling tower, and exposes as much water surface area as possible for maximum air-water contact. As the water flows through the cooling tower, it is exposed to air, which is being pulled through the tower by the electric motor-driven fan. When the water and air meet, a small amount of water is evaporated, creating a cooling action. The cooled water is then pumped back to the condenser or process equipment where it absorbs heat. It will then be re-cycled back to the cooling tower to be cooled once again.
There are two main types of Cooling Tower, these being:
These cooling tower types have the same design system purpose as described above, however the Closed circuit cooling towers operate in a manner similar to open cooling towers, except that the heat load to be rejected is transferred from the process fluid (the fluid being cooled) to the ambient air through a heat exchange coil. The coil serves to isolate the process fluid from the outside air, keeping it clean and contaminate free in a closed loop. This creates two separate fluid circuits: (1) an external circuit, in which spray water circulates over the coil and mixes with the outside air, and (2) an internal circuit, in which the process fluid circulates inside the coil. During operation, heat is transferred from the internal circuit, through the coil to the spray water, and then to the atmosphere as a portion of the water evaporates.
The configuration of a cooling tower can generally be grouped into two design configurations based on the air-flow direction to water-flow direction, these being counter-flow and cross-flow:
Further characteristics that differentiate the design of a cooling tower is based on the fan. Cooling Towers fans can be applied in an Induced draft or a Forced draft configuration:
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