Carnot Cycle

An ideal reversible, closed thermodynamic cycle in which the working substance goes through the four successive operations of 1) isothermal expansion to a desired point, 2) adiabatic expansion to a desired point, 3) isothermal compression, and 4) adiabatic compression back to its initial state. The Carnot cycle is not an actual thermodynamic cycle but a theoretical construct that provides an upper limit on the efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system.