Comment published on 17 December 2018,
see
Entropy 2018, 20(12), 980.
The Principle of Least Action for Reversible Thermodynamic Processes and Cycles
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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Author to whom correspondence should be addressed.
Entropy 2018, 20(7), 542; https://doi.org/10.3390/e20070542
Received: 24 June 2018 / Revised: 19 July 2018 / Accepted: 20 July 2018 / Published: 21 July 2018
(This article belongs to the Section Thermodynamics)
The principle of least action, which is usually applied to natural phenomena, can also be used in optimization problems with manual intervention. Following a brief introduction to the brachistochrone problem in classical mechanics, the principle of least action was applied to the optimization of reversible thermodynamic processes and cycles in this study. Analyses indicated that the entropy variation per unit of heat exchanged is the mode of action for reversible heat absorption or heat release processes. Minimizing this action led to the optimization of heat absorption or heat release processes, and the corresponding optimal path was the first or second half of a Carnot cycle. Finally, the action of an entire reversible thermodynamic cycle was determined as the sum of the actions of the heat absorption and release processes. Minimizing this action led to a Carnot cycle. This implies that the Carnot cycle can also be derived using the principle of least action derived from the entropy concept.
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Keywords:
principle of least action; optimization problems; reversible thermodynamic processes; Carnot cycle
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MDPI and ACS Style
Zhao, T.; Hua, Y.-C.; Guo, Z.-Y. The Principle of Least Action for Reversible Thermodynamic Processes and Cycles. Entropy 2018, 20, 542. https://doi.org/10.3390/e20070542
AMA Style
Zhao T, Hua Y-C, Guo Z-Y. The Principle of Least Action for Reversible Thermodynamic Processes and Cycles. Entropy. 2018; 20(7):542. https://doi.org/10.3390/e20070542
Chicago/Turabian StyleZhao, Tian; Hua, Yu-Chao; Guo, Zeng-Yuan. 2018. "The Principle of Least Action for Reversible Thermodynamic Processes and Cycles" Entropy 20, no. 7: 542. https://doi.org/10.3390/e20070542
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