Air-refrigeration System

Reversed Carnot cycle

Reversed Carnot cycle is shown in Figure 8.2. It consists of the following processes.

Figure 8.2 P−V and T−S Diagrams for Reversed Carnot Cycle

Process a–b: Absorption of heat by the working fluid from refrigerator at constant low temperature T_L during isothermal expansion.

Process b–c: Isentropic compression of the working fluid with the aid of external work. The temperature of the fluid rises from T_L to T_H.

Process c–d: Isothermal compression of the working fluid during which heat is rejected at constant high temperature T_H.

Process d–a: Isentropic expansion of the working fluid. The temperature of the working fluid falls from T_H to T_L.

COP of Refrigerator

Practical use of the reversed Carnot cycle is not possible for refrigeration purpose as the isentropic process requires very high speed operation, whereas the isothermal process requires very low speed operation.