What is the Carnot cycle

Carnot cycle

• The Carnot cycle is a theoretical thermodynamic cycle proposed by French physicist Nicolas Sadi Carnot in 1824.
• It provides an upper limit of efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work.
• Conversely, It also provides the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system.
• It is not an actual thermodynamic cycle but is a theoretical construct.
• The Carnot cycle consists of an alternate series of two reversible isothermal processes and two reversible adiabatic processes.

1.     Isothermal expansion process ab: - During the process ab, heat is transferred          reversibly and isothermally to the working substance from the high-temperature reservoir (HTR) at temperature T_H and the system performs an amount of work.

2.     Adiabatic expansion(dc): - During this process (bc), the temperature of the system decreases from T_H to T_C. 

3.     Isothermal compression process (cd): - During process cd, the system rejects heat Q₂ to a low-temperature reservoir (LTR) at a constant temperature T_C.

4.     Adiabatic compression: - This is the final step. During this process, the temperature rises from T_C to T_H and the original conditions are restored to the system.

• The enclosed area ' abcd ' represents the net work delivered by the engine.