Reversed Heat Engines ]

The performance parameter for heat pumps and refrigerators is termed as the coefficient of performance (COP) that relates the heat quantity of main interest in each device to the total work input. With refrigerator plants, the needed output is heat transfer from the low-temperature area, whereas in heat pump plants, it is the heat transfer to the high-temperature area. It can be easily shown that C_HP = C_R +1. In order to avoid perplexity, C_HP is at times termed to as the ‘performance energy ratio’ (PER), though this usage is not worldwide.