Heat pump (theory)

A heat pump is a refrigerator, with the 'business end' on the hot side. A refrigerator and a heat pump are the same machine: turned round.

A heat pump takes heat from a cold reservoir Q1, (outside a house in a cold climate), and transfers heat Q2 to a warm reservoir, (the inside of a house). The heat transferred to the house Q2 is equal to (Q1+DW).

Heat pumps are desirable because Q2, is larger than DW. Remarkably, the second law of thermodynamics is not violated, but the heat transferred to the house is greater than DW, the heat paid for.

The coefficient of performance of a heat pump is defined as the heat transferred to the warm reservoir over the work required to do the transfer.

Cp is greater than 1 for a Carnot heat pump.

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