The reported discrepancy between theory and experiment for external combustion Stirling engines is explained by the addition of thermal resistance of the combustion gasses to the standard Carnot model. In these cases, the Stirling engine ideal efficiency is not as is normally reported equal to the Carnot cycle efficiency but is significantly lower. A new equation for ideal Stirling engine effic...

We want to understand whether and to what extent the maximal (Carnot) efficiency for heat engines can be reached at a finite power. To this end we generalize the Carnot cycle so that it is not restricted to slow processes. We show that for realistic (i.e., not purposefully designed) engine-bath interactions, the work-optimal engine performing the generalized cycle close to the maximal efficienc...

In the paper by Abe and Okuyama [Phys. Rev. E 83, 021121 (2011)], the quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is discussed. It is claimed that the state at the beginning of the quantum Carnot cycle is pure. After that, it is apparently transmuted to a mixed state if Clausius equality is imposed. We prove that this stat...

The efficiency of the ideal stirling cycle assumes, that the cylinder volumes are isothermal and that the temperatures in the cylinder volumes are identical to the temperatures in the heat sink and the heat source. The efficiency is then identical to the efficiency of the Carnot cycle. However, in a real stirling machine the cylinder volumes are nearly adiabatic instead of isothermal, and the h...

The Carnot cycle and the attendant notions of reversibility entropy are examined. It is shown how modern view these concepts still corresponds to ideas Clausius laid down in nineteenth century. As such, they reflect outmoded idea, current at time, that heat motion. this led develop a body based on work could be performed reversible process rather than actually an irreversible process. In conseq...

Carnot established in 1824 that the efficiency ηC of reversible engines operating between a hot bath at absolute temperature Thot and a cold bath at temperature Tcold is equal to 1−Tcold/Thot. Carnot particularly considered air as a working fluid and small bath-temperature differences. Plugging into Carnot’s expression modern experimental values, exact agreement with modern Thermodynamics is fo...