Chin. Phys. B ›› 2013, Vol. 22 ›› Issue (1): 10508-010508.doi: 10.1088/1674-1056/22/1/010508

• GENERAL • 上一篇    下一篇

Applicability of minimum entropy generation methodto optimizing thermodynamic cycles

程雪涛, 梁新刚   

  1. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,School of Aerospace, Tsinghua University, Beijing 100084, China
  • 收稿日期:2012-04-07 修回日期:2012-06-20 出版日期:2012-12-01 发布日期:2012-12-01
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 51106082) and the Tsinghua University Initiative Scientific Research Program, China.

Applicability of minimum entropy generation methodto optimizing thermodynamic cycles

Cheng Xue-Tao (程雪涛), Liang Xin-Gang (梁新刚)   

  1. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,School of Aerospace, Tsinghua University, Beijing 100084, China
  • Received:2012-04-07 Revised:2012-06-20 Online:2012-12-01 Published:2012-12-01
  • Contact: Liang Xin-Gang E-mail:liangxg@tsinghua.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 51106082) and the Tsinghua University Initiative Scientific Research Program, China.

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摘要： Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed.

关键词: entropy generation, thermodynamic cycles, heat-work conversion, optimization

Abstract: Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed.

Key words: entropy generation, thermodynamic cycles, heat-work conversion, optimization

中图分类号:  (Nonequilibrium and irreversible thermodynamics)

  • 05.70.Ln
95.30.Tg (Thermodynamic processes, conduction, convection, equations of state) 65.40.gd (Entropy)