page_title: Stirling cycle
section_title: Idealized Stirling cycle thermodynamics
hierarchical_section_title: Stirling cycle / Idealized Stirling cycle thermodynamics
context_page_description: The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices. This includes the original Stirling engine that was invented, developed and patented in 1816 by Robert Stirling with help from his brother, an engineer.
  The ideal Otto and Diesel cycles are not totally reversible because they involve heat transfer through a finite temperature difference during the irreversible isochoric/isobaric heat-addition and heat-rejection processes. The irreversibility renders the thermal efficiency of these cycles less than that of a Carnot engine operating within the same limits of temperature. Another cycle that features isothermal heat-addition and heat-rejection processes is the Stirling cycle, which is an altered version of the Carnot cycle in which the two isentropic processes featured in the Carnot cycle are replaced by two constant-volume regeneration processes.
  The cycle is reversible, meaning that if supplied with mechanical power, it can function as a heat pump for heating or cooling, and even for cryogenic cooling. The cycle is defined as a closed regenerative cycle with a gaseous working fluid.
context_section_description: The idealized Stirling cycle consists of four thermodynamic processes acting on the working fluid (See diagram to right):
  1-2 Isothermal heat addition (expansion).
  2-3 Isochoric heat removal (constant volume).
  3-4 Isothermal heat removal (compression).
  4-1 Isochoric heat addition (constant volume).
caption: A pressure/volume graph of the idealized Stirling cycle. In real applications of the Stirling cycles (e.g. Stirling engines) this cycle is quasi-elliptical.