Coefficient of performance

1 The coefficient of performance for a refrigerator is defined as the heat removed from the cold box (Q1) divided by the energy input to the refrigerator (DW) [the energy we have to pay for].

2 The coefficient of performance for a heat pump is defined as the heat transferred to the warm reservoir (Q2) over the work required to do the transfer, (DW).

A heat pump transfers heat from a cold reservoir and work (input power) is converted to heat. The coefficient of performance can be greater than 1.

Note: all real refrigerators and heat pumps will have a lower coefficient of performance than that of the equivalent Carnot device.

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