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A '''heat pump''' is a [[heat engine]] operating in reverse. Common [[air conditioner]]s and [[refrigerator]]s are well-known examples of heat pumps. | A '''heat pump''' is a [[heat engine]] operating in reverse. Common [[air conditioner]]s and [[refrigerator]]s are well-known examples of heat pumps. | ||
==Use== | |||
[[Image:HeatAndColdStorageWithHeatPump.jpg|thumb|right|200px|A [[solar thermal collector]] can heat the soil or groundwater in summer, after which a (ground-source) heat pump can pump it back up to heat the house in winter. The system can be attached to conventional radiators]] | |||
The heat pump can be used to [[heating|heat]] or [[cooling|cool]] a space. Also, it can be used to extract or pump [[heat]] either into or out of a space. For [[home heating]], a heat pump can extract heat from outside air (even at temperatures below freezing), or from the ground through liquid circulated through subsoil pipes.This heat can then be transferred indoors. During hot weather, the cycle is reversed; heat is extracted from the indoor air and expelled to the outside as in an [[air conditioner]] or [[refrigerator]]. | The heat pump can be used to [[heating|heat]] or [[cooling|cool]] a space. Also, it can be used to extract or pump [[heat]] either into or out of a space. For [[home heating]], a heat pump can extract heat from outside air (even at temperatures below freezing), or from the ground through liquid circulated through subsoil pipes.This heat can then be transferred indoors. During hot weather, the cycle is reversed; heat is extracted from the indoor air and expelled to the outside as in an [[air conditioner]] or [[refrigerator]]. | ||
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During the [[heating mode]], the outdoor coil is the evaporator and the indoor coil is the condenser. | During the [[heating mode]], the outdoor coil is the evaporator and the indoor coil is the condenser. | ||
# The [[refrigerant]] absorbs heat in the evaporator from the outdoor air, turning into [[gas]] | |||
# The [[compressor]] raises the [[pressure]] of the gas, which also increases its temperature | |||
# The hot gas then flows through the condenser coils that are inside the heated space | |||
# The liquid then flows back through a pressure-reducing valve (capillary tube)to the outdoor evaporator coils, being cooled through expansion | |||
* '''Cooling Cycle''' | * '''Cooling Cycle''' | ||
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The efficiency used for heat pumps is not expressed in terms of the ratio of energy output to energy input, but expressed in terms of the ratio of energy output to work input. In other words known as the, [[Coefficient of performance]] or COP. | The efficiency used for heat pumps is not expressed in terms of the ratio of energy output to energy input, but expressed in terms of the ratio of energy output to work input. In other words known as the, [[Coefficient of performance]] or COP. | ||
== External links == | |||
== | |||
* [[Wikipedia:Heat pump]] | * [[Wikipedia:Heat pump]] | ||
[[Category:PH261]] | [[Category:PH261]] | ||
[[Category:Heating and cooling]] | [[Category:Heating and cooling]] | ||
Revision as of 16:42, 27 April 2013
A heat pump is a heat engine operating in reverse. Common air conditioners and refrigerators are well-known examples of heat pumps.
Use
The heat pump can be used to heat or cool a space. Also, it can be used to extract or pump heat either into or out of a space. For home heating, a heat pump can extract heat from outside air (even at temperatures below freezing), or from the ground through liquid circulated through subsoil pipes.This heat can then be transferred indoors. During hot weather, the cycle is reversed; heat is extracted from the indoor air and expelled to the outside as in an air conditioner or refrigerator.
Basic Components
- Heating Mode
During the heating mode, the outdoor coil is the evaporator and the indoor coil is the condenser.
- The refrigerant absorbs heat in the evaporator from the outdoor air, turning into gas
- The compressor raises the pressure of the gas, which also increases its temperature
- The hot gas then flows through the condenser coils that are inside the heated space
- The liquid then flows back through a pressure-reducing valve (capillary tube)to the outdoor evaporator coils, being cooled through expansion
- Cooling Cycle
During the cooling cycle the evaporator and condenser coils exchange roles. The direction of flow of the refrigerant is reversed with a special valve.
Efficiency
The efficiency used for heat pumps is not expressed in terms of the ratio of energy output to energy input, but expressed in terms of the ratio of energy output to work input. In other words known as the, Coefficient of performance or COP.