ABSTRACT
Heat engines operate in a cyclic way by taking in heat Q1 from a hightemperature reservoir, converting part of this energy into work output W and rejecting the remainder Q2 to a low-temperature reservoir. Figure 3.1 shows the heat transferred and the work done in one complete cycle of a heat engine. e eªciency η of a heat engine is deˆned as
h = = W Q
W Q
in 1 .(3.1)
A natural question that arises concerns the maximum possible eªciency of a heat engine. is question was addressed in the nineteenth century by Sadi Carnot, who considered a reversible cyclic engine with an ideal gas as the work substance. In honor of Carnot, the ideal engine is called a Carnot engine. Figure 3.2 is a P-V diagram that depicts the cyclic operation of an ideal gas Carnot engine. e gas is contained in a cylinder ˆtted with a frictionless piston that can be moved very slowly and reversibly to change the volume. e Carnot cycle consists of two reversible quasi-static isothermal processes that involve the gas system in contact with heat baths at temperatures T1 and T2, respectively, and two reversible adiabatic processes in which the gas and the container are thermally isolated from the surroundings.
