Cycle, Thermodynamic

a cycle that is completed by a thermodynamic system. The cycles studied in thermodynamics are combinations of various thermodynamic processes, primarily isothermal, adiabatic, isobaric, and isochoric processes.

Figure 1. Thermodynamic cycles in volume (V)-pressure (p) coordinates: (a) the Carnot cycle, (b) the Clapeyron cycle, (c) the Clausius-Rankine cycle

The Carnot cycle (Figure 1, a), the Clapeyron cycle (Figure 1, b), and the Clausius-Rankine cycle (Figure l,c; seeRANKINE CYCLE) are some of the thermodynamic cycles that have played an important role in the evolution of the general principles of thermodynamics and in the development of engineering applications of thermodynamics. Such thermodynamic cycles have been used to study general regularities of the operation of heat engines— that is, internal-and external-combustion engines and turbines— and refrigeration units. (See; STIRLING ENGINE; and WANKEL ENGINE.)