Editing Cooling tower (section)

===Heating, ventilation and air conditioning (HVAC)===
[[File:Loop Shopping Centre Exterior I.jpg|thumb|Two HVAC cooling towers on the rooftop of a shopping center (Darmstadt, Hessen, Germany)]]
{{main|HVAC}}

[[File:Induced Draft Cooling Tower for HVAC.jpg|thumb|FRP cooling towers installed on roof top]]

[[File:Cooling Tower Fill Material.jpg|thumb|right|Cell of a cross-flow type cooling tower with fill material and circulating water visible]]

An [[HVAC]] (heating, ventilating, and air conditioning) cooling tower is used to dispose of ("reject") unwanted heat from a [[chiller]]. Liquid-cooled chillers are normally more energy efficient than air-cooled chillers due to [[heat rejection]] to tower water at or near [[wet-bulb temperature]]s.  Air-cooled chillers must reject heat at the higher [[dry-bulb temperature]], and thus have a lower average reverse–[[Carnot cycle|Carnot-cycle]] effectiveness. In hot climates, large office buildings, hospitals, and schools typically use cooling towers in their air conditioning systems.  Generally, industrial cooling towers are much larger than HVAC towers.
HVAC use of a cooling tower pairs the cooling tower with a liquid-cooled chiller or liquid-cooled condenser. A [[Refrigeration#Capacity ratings|''ton'' of air-conditioning]] is defined as the removal of {{convert|12,000|BTU/h|kW}}. The ''equivalent ton'' on the cooling tower side actually rejects about {{convert|15,000|BTU/h|kW}} due to the additional waste-heat–equivalent of the energy needed to drive the chiller's compressor. This ''equivalent ton'' is defined as the heat rejection in cooling {{convert|3|usgal/minute|L/minute|abbr=off}} or {{convert|1,500|lb/h|kg/h}} of water by {{convert|10|F-change|C-change}}, which amounts to {{convert|15,000|BTU/h|kW}}, assuming a chiller [[coefficient of performance]] (COP) of 4.0.<ref>{{cite book|last1=Cheremisinoff|first1=Nicholas|title=Handbook of Chemical Processing Equipment|date=2000|publisher=Butterworth-Heinemann|isbn=9780080523828|page=69}}</ref> This COP is equivalent to an energy efficiency ratio (EER) of 14.

Cooling towers are also used in HVAC systems that have multiple water source [[heat pumps]] that share a common piping ''water loop''. In this type of system, the water circulating inside the water loop removes heat from the condenser of the heat pumps whenever the heat pumps are working in the cooling mode, then the externally mounted cooling tower is used to remove heat from the water loop and reject it to the [[atmosphere]].  By contrast, when the heat pumps are working in heating mode, the condensers draw heat out of the loop water and reject it into the space to be heated.  When the water loop is being used primarily to supply heat to the building, the cooling tower is normally shut down (and may be drained or winterized to prevent freeze damage), and heat is supplied by other means, usually from separate [[boiler]]s.