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An HVAC cooling tower is a subcategory rejecting
heat from a chiller. Water-cooled chillers are
normally more energy efficient than air-cooled
chillers due to heat rejection to tower water at
or near wet-bulb temperatures. Air-cooled
chillers must reject heat at the dry-bulb
temperature, and thus have a lower average
reverse-Carnot cycle effectiveness. Large office
buildings, hospitals, and schools typically use
one or more cooling towers as part of 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 water-cooled chiller or
water-cooled condenser. A ton of
air-conditioning is the removal of 12,000
Btu/hour (3517 W). The equivalent ton on the
cooling tower side actually rejects about 15,000
Btu/hour (4396 W) due to the heat-equivalent of
the energy needed to drive the chiller's
compressor. This equivalent ton is defined as
the heat rejection in cooling 3 U.S.
gallons/minute (1,500 pound/hour) of water 10 °F
(5.56 °C), which amounts to 15,000 Btu/hour, or
a chiller coefficient-of-performance (COP) of
4.0. This COP is equivalent to an energy
efficiency ratio (EER) of 13.65. |
