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A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem, it provides an upper limit on the efficiency of any classical thermodynamic engine during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference through ...
Axial cross section of Carnot's heat engine. In this diagram, abgh is a cylindrical vessel, cd is a movable piston, and A and B are constant–temperature bodies. The vessel may be placed in contact with either body or removed from both (as it is here). [1] A Carnot heat engine [2] is a theoretical heat engine that operates on the Carnot cycle.
The Carnot cycle is a cycle composed of the totally reversible processes of isentropic compression and expansion and isothermal heat addition and rejection. The thermal efficiency of a Carnot cycle depends only on the absolute temperatures of the two reservoirs in which heat transfer takes place, and for a power cycle is:
Carnot understood that the conduction of heat between bodies at different temperatures is a wasteful and irreversible process, which must be minimized if the heat engine is to achieve its maximum efficiency. Carnot cycle in a pressure vs. volume diagram. This graphical representation of Carnot's cycle was introduced by Émile Clapeyron in 1834.
The book is considered the founding work of thermodynamics. [2]: viii It contains the preliminary outline of the second law of thermodynamics.Carnot stated that motive power is due to the fall of caloric (chute de calorique) from a hot to a cold body, which he analogized to the work done by a water wheel due to a waterfall (chute d'eau).
The thermodynamic definition of entropy was developed in the early 1850s by Rudolf Clausius and essentially describes how to measure the entropy of an isolated system in thermodynamic equilibrium with its parts. Clausius created the term entropy as an extensive thermodynamic variable that was shown to be useful in characterizing the Carnot cycle.
Since a Carnot heat engine is a reversible heat engine, and all reversible heat engines operate with the same efficiency between the same reservoirs, we have the first part of Carnot's theorem: No irreversible heat engine is more efficient than a Carnot heat engine operating between the same two thermal reservoirs.
With the ideal, maximally efficient, Stirling engine, for the thermal reservoirs the ratio of the heat in to the heat out is the efficiency of the ideal Carnot cycle. This is the Carnot efficiency, which is the ratio of the Kelvin temperatures of the cold to the hot reservoir. With the ideal, maximally efficient, Carnot cycle, the isochores ...