The performance of a heat pump degrades (i.e., its COP decreases) as the temperature of the heat source decreases. This makes us
ing heat pumps at locations with severe weather conditions unattractive. Consider a house that is heated and maintained at 26°C by a heat pump during the winter. What is the maximum COP for the heat pump if heat is extracted the out door air at 10 C?
Temperature at which heat is extracted; T_L = 10°C = 273 + 10 = 283K
Now the Coefficient of performance (COP) of a heat pump will be a maximum when the heat pump operates in a reversible manner. The COP of a reversible heat pump depends on the temperature limits in the cycle only and is determined by the formula;
