Temperature Limitations for Reversed Carnot Cycle:

We already have seen that the C.O.P. of the reversed Carnot cycle is described by,

Here

T₁ = Lower temperature, &

T₂ = Higher temperature.

The C.O.P. of the reversed Carnot cycle may be enhanced by

(1) Declining the higher temperature (that is temperature of hot body, T₂) or

(2) Enhancing the lower temperature (that is. temperature of cold body, T₁). This can be noted down that temperature T₁ and T₂ cannot be varied at will, because of certain functional limitations. It must be kept in mind that the higher temperature (T₂) is the temperature of cooling water or air available for refusal of heat & the lower temperature (T₁) is the temperature that maintained in the refrigerator. The heat transfer shall take place in the right direction just when the higher temperature is more than the cooling water temperature or air to which heat is to be discarded, while the lower temperature ought to be less than the temperature of substance to be cooled up.

Therefore if the temperature of cooling water or air (that is T₂) available for heat denial is low, the C.O.P. shall be high. As T₂ in winter is less than T₂ in summer, thus, C.O.P. in winter shall be higher than C.O.P. in summer. In other terms, the Carnot refrigerator works more capably in winter than in summer. Likewise, if the lower temperature (T₁) is high, the C.O.P. of the Carnot refrigerator shall be high.