The Carnot cycle, developed by Sadi Carnot in the 19th century, is a theoretical cycle that describes the maximum efficiency of a heat engine operating between...
The Carnot cycle, developed by Sadi Carnot in the 19th century, is a theoretical cycle that describes the maximum efficiency of a heat engine operating between two temperatures, namely, a hot reservoir at a constant temperature T_H and a cold reservoir at a constant temperature T_C.
The Carnot engine operates based on the Second Law of Thermodynamics, which states that the efficiency of a heat engine is bounded by the temperatures of the two reservoirs. In other words, it is impossible to reach 100% efficiency, regardless of the material or operating conditions of the engine.
The efficiency of a heat engine is defined as the ratio of the work done by the engine to the heat input. Since the engine operates between two reservoirs at constant temperatures, the work done by the engine is equal to the heat input. Therefore, the efficiency of a Carnot engine is equal to 100%.
The Carnot cycle consists of two main processes:
Isentropic expansion of the working fluid (from state 1 to state 2).
Isentropic compression of the working fluid (from state 3 to state 4).
During the isentropic expansion, the working fluid's temperature decreases, while its pressure remains constant. This process is reversible, meaning the working fluid's temperature and pressure return to their initial values.
During the isentropic compression, the working fluid's temperature increases, while its pressure remains constant. This process is also reversible.
The net work done by the engine during one cycle is equal to the difference between the heat input and the heat rejected by the engine. Since the efficiency of the Carnot engine is 100%, the net work is also equal to zero.
The efficiency of a Carnot engine provides an upper bound for the efficiency of all real heat engines operating between the same two temperatures. It is a theoretical benchmark for the performance of a heat engine