A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream, to a lower temperature. Cooling towers may either use the evaporation of water to remove heat and cool the working fluid to near the wet-bulb air temperature or, in the case of dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature using radiators.
A typical evaporative, forced draft open-loop cooling tower rejecting heat from the condenser water loop of an industrial chiller unit
Natural draft wet cooling hyperboloid towers at Didcot Power Station (UK)
Forced draft wet cooling towers (height: 34 meters) and natural draft wet cooling tower (height: 122 meters) in Westphalia, Germany
Natural draft wet cooling tower in Dresden (Germany)
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, incandescent light bulbs get hot, a refrigerator warms the room air, a building gets hot during peak hours, an internal combustion engine generates high-temperature exhaust gases, and electronic components get warm when in operation.
Thermal oxidizers can use a regenerative process for waste heat from industrial systems.
Air conditioning units extract heat from a dwelling interior with coolant, and transfer it to the dwelling exterior as waste. They emit additional heat in their use of electricity to power the devices that pass heat to and from the coolant.
Cooling towers evaporating water at Ratcliffe-on-Soar Power Station, United Kingdom
