Coefficient of Performance COP

Heat engine thermal efficiency considers the amount of work that is produced from a given heat supply. With the refrigeration cycle, performance measurement — termed coefficient of performance (COP) — considers the amount of work required to remove a given amount of heat from the low-temperature source. Performance is optimized when input work is minimized at a given load.

Based on Figure 33-1, refrigeration cycle COP can be described as the ratio of the refrigeration effect (the amount of heat the system removes from the conditioned space or process load, Qin) to work input (the net amount of energy transferred into the system to accomplish the refrigeration effect, Wcycle). Thus, the COP is expressed as:

Refrigeration effect Qin

Work inPut Wcycle


Wycle = Net work required to drive refrigerator (Qout- Qin). If we let Qin = 1 ton of refrigeration, then equation (33-1) leads to the following convenient relationships:


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