Carnot Cycle

Heat engines like steam engine, gasoline engine, diesel engine or steam turbine convert heat to mechanical energy. They are based on cyclic processes in which the same states are passed through again and again. The Carnot process, proposed and studied by Nicolas Léonard Sadi Carnot in 1824, is a special cyclic process significant for the theory of heat engines. It is an idealized process for which the efficiency can be calculated rather easily.

An ideal gas (shown here in green) passes successively through the following processes:

This app alternatively shows the experimental setup with two small diagrams, a large P-V diagram (relationship between pressure and volume) or a large T-S diagram (relationship between temperature and entropy). The following sizes can be entered in the input fields:

Sometimes the entered values must be changed by the program. The minimal and maximal pressure are calculated with the gas equation and displayed in the unit kPa (kilopascal).

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Efficiency of a Carnot engine:

η  =  1 − TC

η  .... efficiency
TC  ... absolute temperature of the cold reservoir
TH  ... absolute temperature of the hot reservoir

The efficiency of a real heat engine operating between two thermal reservoirs is always lower than the efficiency of a corresponding Carnot engine.