How Heat Pumps Work

Heat pumps extract energy from the environment in order to heat water for use in the home. They can be used to extract energy from the ground, air or water depending on which model is used.

The heat pump cycle

The refrigerant in the heat pump's evaporator is heated by low-grade heat from a connected air exchanger, a ground array/borehole or open/closed loop water system. The heated refrigerant gas is then squeezed by the compressor into the condenser where the absorbed heat is transferred to the heating system water via a heat exchanger.

Main components in detail

Evaporator: Used to transfer heat from the environment to the refrigerant in the heat pump. This is a metal heat exchanger filled with refrigerant at a sufficiently low pressure so that it can be boiled by the surrounding low-grade heat from the environment.

Compressor: Used to compress the low pressure, low temperature refrigerant from the evaporator into high pressure, high temperature refrigerant vapour and transfer it to the condenser. The compressor is the main component of the heat pump and requires electricity to operate.

Condenser: Used to transfer heat from the high temperature refrigerant to the heating system. The refrigerant condenses back into a liquid as it's heat is given up to the heating system water.

Expansion Valve: A very small orifice through which the refrigerant liquid is pushed into the evaporator to make it expand and cool down to begin the cycle again.

External links

• Wikipedia - Heat Pumps
• Energy Saving Trust - Air Source Heat Pumps
• Energy Saving Trust - Ground Source Heat Pumps

Wikipedia - Heat Pumps

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