Unconventional cycles and multiple adiabatic points

The so-called unconventional cycles provide a useful didactic resource to discuss the second law of thermodynamics applied to heat engines and their efficiency. In the simplest, previous and thoroughly studied case involving a negatively sloped linear process, interesting physics follow from the pre...

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Bibliographic Details
Published in:European journal of physics 2018-11, Vol.39 (6), p.65103
Main Author: Arenzon, Jeferson J
Format: Article
Language:English
Subjects:
circular cycle
heat engines
second law
unconventional cycles
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Summary:The so-called unconventional cycles provide a useful didactic resource to discuss the second law of thermodynamics applied to heat engines and their efficiency. In the simplest, previous and thoroughly studied case involving a negatively sloped linear process, interesting physics follow from the presence of an adiabatic point. At such point, the process is tangent to an adiabatic curve and δQ = 0, signalling where the heat flow is reversed. In order to deal with the follow up question on the possibility of having more than one adiabatic point, we introduce a parabolic process whose behavior is richer but still amenable to analytical exploration. In addition, we define pseudoadiabatic processes that are reversible and non-isoentropic, but whose total heat exchanged is zero. These processes are useful when emphasizing the necessary and sufficient conditions for an actual adiabatic process. The linear-parabolic cycle is then introduced, and a few particular cases are discussed.
ISSN:0143-0807
1361-6404
DOI:10.1088/1361-6404/aadaef