• Cooling towers use pumps, shells and air flow systems to cool water.geometric image by Andrei Merkulov from Fotolia.com
  
  A cooling tower is a device designed to cool water down. Many cooling towers cool water as part of a broader process, so the cool water can go on to cool down air, reactors or other systems. The cooling tower is similar to a plumbing system or air-conditioning unit but operates on slightly different principles, using a number of different parts to help evaporate the water.
  
  

Pumps

• Pumps and related pipes pump the water up to the top of the tower. Depending on the size of the tower, the pump may need a powerful motor in order to transport the water vertically. Most systems draw this water in from another source, such as a cooling systems located inside a building. The tower itself is built beside or on top of the building.
  
  

Shells

• Shells are layers in the tower, typically placed in honeycomb patterns. Once the water is pumped to the top of the tower, it is allowed to fall freely back down through the shells. This maximizes the surface area of the water and allows more of it to come in contact with the air. This gives the water a greater chance to evaporate. Cooling towers do not evaporate all of the water but they do allow enough the water to evaporate to carry away the heat the water holds, cooling it and making it ready to enter the system again.
  
  

Air Flow

• There are two different types of air flow systems that cooling towers use. The first kind uses a force air system that draws air in from the outside and circulates it through the shells so it is exposed to the water. The second type of system has open shells that are naturally exposed to outside air and allow for more free evaporation.
  
  

Filters and Fans

• If the air flow system is open-air, it needs to use a series of filters, such as sand and gravel filters, to help catch debris. The water is exposed to contaminants in the open air and they must be removed before the water re-enters the building. If the tower uses a closed-off system, it needs fans to help circulate the air.