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Research Papers: Energy Systems Analysis

Specific Entropy Generation in a Gas Turbine Power Cycle

[+] Author and Article Information
Y. Haseli

School of Engineering and Technology,
Central Michigan University,
Mount Pleasant, MI 48859

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received July 12, 2017; final manuscript received August 28, 2017; published online September 28, 2017. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 140(3), 032002 (Sep 28, 2017) (8 pages) Paper No: JERT-17-1356; doi: 10.1115/1.4037902 History: Received July 12, 2017; Revised August 28, 2017

Numerous studies have shown that the minimization of entropy generation does not always lead to an optimum performance in energy conversion systems. The equivalence between minimum entropy generation and maximum power output or maximum thermal efficiency in an irreversible power cycle occurs subject to certain design constraints. This article introduces specific entropy generation defined as the rate of total entropy generated due to the operation of a power cycle per unit flowrate of fuel. Through a detailed thermodynamic modeling of a gas turbine cycle, it is shown that the specific entropy generation correlates unconditionally with the thermal efficiency of the cycle. A design at maximum thermal efficiency is found to be identical to that at minimum specific entropy generation. The results are presented for five different fuels including methane, hydrogen, propane, methanol, and ethanol. Under identical operating conditions, the thermal efficiency is approximately the same for all five fuels. However, a power cycle that burns a fuel with a higher heating value produces a higher specific entropy generation. An emphasis is placed to distinguish between the specific entropy generation (with the unit of J/K mol fuel) and the entropy generation rate (W/K). A reduction in entropy generation rate does not necessarily lead to an increase in thermal efficiency.

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References

Haseli, Y. , 2011, “ Substance Independence of Efficiency of a Class of Heat Engines Undergoing Two Isothermal Processes,” J. Thermodyn., 2011, p. 647937. [CrossRef]
Leff, H. S. , and Jones, G. L. , 1975, “ Irreversibility, Entropy Production, and Thermal Efficiency,” Am. J. Phys., 43(11), pp. 973–980. [CrossRef]
Haseli, Y. , 2013, “ Performance of Irreversible Heat Engines at Minimum Entropy Generation,” Appl. Math. Model., 37(23), pp. 9810–9817. [CrossRef]
Haseli, Y. , 2013, “ Optimization of Regenerative Brayton Cycle by Maximization of a Newly Defined Second Law Efficiency,” Energy Convers. Manage., 68, pp. 133–140. [CrossRef]
Haseli, Y. , 2016, “ Efficiency of Irreversible Brayton Cycles at Minimum Entropy Generation,” Appl. Math. Model., 40(19–20), pp. 8366–8376. [CrossRef]
Feidt, M. , Costea, M. , Petrescu, S. , and Stanciu, C. , 2016, “ Nonlinear Thermodynamic Analysis and Optimization of a Carnot Engine Cycle,” Entropy, 18(7), p. 243. [CrossRef]
Cheng, X. T. , and Liang, X. G. , 2013, “ Discussion on the Applicability of Entropy Generation Minimization to the Analyses and Optimizations of Thermodynamic Processes,” Energy Convers. Manage., 73, pp. 121–127. [CrossRef]
Cheng, X. T. , and Liang, X. G. , 2012, “ Heat-Work Conversion Optimization of One-Stream Heat Exchanger Network,” Energy, 47(1), pp. 421–429. [CrossRef]
Sun, C. , Cheng, X. T. , and Liang, X. G. , 2014, “ Output Power Analyses for the Thermodynamic Cycles of Thermal Power Plants,” Chin. Phys. B, 23(5), p. 050513. [CrossRef]
Li, T. , Fu, W. , and Zhu, J. , 2014, “ An Integrated Optimization for Organic Rankine Cycle Based on Entransy Theory and Thermodynamics,” Energy, 72, pp. 561–573. [CrossRef]
Zhou, B. , Tao Cheng, X. , Wang, W. H. , and Liang, X. G. , 2015, “ Entransy Analyses of Thermal Processes With Variable Thermophysical Properties,” Int. J. Heat Mass Transfer, 90, pp. 1244–1254. [CrossRef]
Klein, S. A. , and Reindl, D. T. , 1998, “ The Relationship of Optimum Heat Exchanger Allocation and Minimum Entropy Generation Rate for Refrigeration Cycles,” ASME J. Energy Resour. Technol., 120(2), pp. 172–178. [CrossRef]
Shah, R. K. , and Skiepko, T. , 2004, “ Entropy Generation Extrema and Their Relationship With Heat Exchanger Effectiveness—Number of Transfer Unit Behavior for Complex Flow Arrangements,” ASME J. Heat Transfer, 126(6), pp. 994–1002. [CrossRef]
Qian, X. , and Li, Z. , 2011, “ Analysis of Entransy Dissipation in Heat Exchangers,” Int. J. Therm. Sci., 50(4), pp. 608–614. [CrossRef]
Cheng, X. T. , 2013, “ Entropy Resistance Minimization: An Alternative Method for Heat Exchanger Analyses,” Energy, 58, pp. 672–678. [CrossRef]
Chakraborty, S. , and Ray, S. , 2011, “ Performance Optimisation of Laminar Fully Developed Flow Through Square Ducts With Rounded Corners,” Int. J. Therm. Sci., 50(12), pp. 2522–2535. [CrossRef]
Fakheri, A. , 2010, “ Second Law Analysis of Heat Exchangers,” ASME J. Heat Transfer, 132(11), p. 111802. [CrossRef]
Haseli, Y. , 2016, “ The Equivalence of Minimum Entropy Production and Maximum Thermal Efficiency in Endoreversible Heat Engines,” Heliyon, 2(5), p. e00113. [CrossRef] [PubMed]
Bejan, A. , 1996, “ Models of Power Plants That Generate Minimum Entropy While Operating at Maximum Power,” Am. J. Phys., 64(8), pp. 1054–1059. [CrossRef]
Bejan, A. , 1996, “ The Equivalence of Maximum Power and Minimum Entropy Generation Rate in the Optimization of Power Plants,” ASME J. Energy Resour. Technol., 118(2), pp. 98–101. [CrossRef]
Salamon, P. , Hoffmann, K. H. , Schubert, S. , Berry, R. S. , and Andresen, B. , 2001, “ What Conditions Make Minimum Entropy Production Equivalent to Maximum Power Production,” J. Non-Equilib. Thermodyn., 26(1), pp. 73–83. [CrossRef]
Bejan, A. , 2017, “ Evolution in Thermodynamics,” Appl. Phys. Rev., 4(1), p. 011305. [CrossRef]
Leff, H. S. , 1996, “ Thermodynamic Entropy: The Spreading and Sharing of Energy,” Am. J. Phys., 64(10), pp. 1261–1271. [CrossRef]
Lambert, F. L. , 2002, “ Entropy is Simple, Qualitatively,” J. Chem. Educ., 79(10), pp. 1241–1246.
Lambert, F. L. , 2002, “ Disorder—A Crack Crutch for Supporting Entropy Discussions,” J. Chem. Educ., 79(2), pp. 187–192. [CrossRef]
Borgnakke, C. , and Sonntag, R. E. , 2013, Fundamentals of Thermodynamics, 8th ed., Wiley, Hoboken, NJ.
Gyftopoulos, E. P. , and Beretta, G. P. , 1993, “ Entropy Generation Rate in a Chemically Reacting System,” ASME J. Energy Resour. Technol., 115(3), pp. 208–212. [CrossRef]
Linstrom, P. J. , and Mallard, W. G. , 2017, “ NIST Chemistry WebBook, NIST Standard Reference Database Number 69,” National Institute of Standards and Technology, Gaithersburg MD, accessed Sept. 20, 2017, http://webbook.nist.gov/
Haseli, Y. , 2011, Thermodynamic Optimization of Power Plants, Eindhoven University of Technology, Eindhoven, The Netherlands.
Wang, Y. , Ding, X. , Tang, L. , and Weng, Y. , 2016, “ Effect of Evaporation Temperature on the Performance of Organic Rankine Cycle in Near-Critical Condition,” ASME J. Energy Resour. Technol., 138(3), p. 032001. [CrossRef]
Ramaprabhu, V. , and Roy, R. P. , 2004, “ A Computational Model of Combined Cycle Power Generation Unit,” ASME J. Energy Resour. Technol., 126(3), pp. 231–240. [CrossRef]
Yu, S. Y. , Chen, L. , Zhao, Y. , Li, H. X. , and Zhang, X. R. , 2015, “ A Brief Review Study of Various Thermodynamic Cycles for High Temperature Power Generation Systems,” Energy Convers. Manage., 94, pp. 68–83. [CrossRef]
Hofmann, M. , and Tsatsaronis, G. , 2016, “ Exergy-Based Study of Binary Rankine Cycle,” ASME J. Energy Resour. Technol., 138(6), p. 062003. [CrossRef]
Demirkaya, G. , Besarati, S. , Padilla, R. V. , Archibold, A. R. , Goswami, D. Y. , Rahman, M. M. , and Stefanakos, E. L. , 2012, “ Multi-Objective Optimization of a Combined Power and Cooling Cycle for Low-Grade and Midgrade Heat Sources,” ASME J. Energy Resour. Technol., 134(3), p. 032002. [CrossRef]

Figures

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Fig. 1

Comparison of the thermal efficiency of a regenerative gas turbine cycle versus the effectiveness of the regenerator at the regime of maximum thermal efficiency, maximum work output, and minimum entropy generation [5]

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Fig. 2

Schematic of a gas turbine cycle

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Fig. 3

Comparison of the present model and a simplified model [3,29]: (a) thermal efficiency and (b) work output (Joule per mole of air)

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Fig. 4

Thermal efficiency (solid lines) and specific entropy generation (dashed lines, unit: J/mol K) of the gas turbine cycle versus the pressure ratio at three different TITs

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Fig. 5

Illustration of entropy generated (J/mol K) due to each irreversible process at the condition of minimum specific entropy generation for three TITs

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Fig. 6

Thermal efficiency (solid lines) and specific entropy generation (dashed lines, unit: J/mol K) of the gas turbine cycle versus the TIT at three different values of pressure ratio (p2/p1)

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Fig. 7

The effect of fuel type on the thermal efficiency (solid lines) and the specific entropy generation (dashed lines, unit: J/mol K) of the cycle. The three different colors correspond to different TITs: 1200 K (blue lines), 1100 K (brown lines), 1000 K (green lines).

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Fig. 8

Comparison of the minimum specific entropy generation (J/mol K) of the cycle operating with different fuels at three TITs. The numbers within the graph are the heating values in kJ/mol.

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Fig. 9

Comparison of the minimum specific entropy generation (J/g K) of the cycle operating with different fuels at three TITs. The numbers within the graph are the heating values in kJ/g.

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Fig. 10

Thermal efficiency (solid lines) and entropy generation rate (dashed lines, unit: kW/K) of the gas turbine cycle versus the pressure ratio at three different TITs; Fuel: methane, air mass flowrate: 2 kg/s

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Fig. 11

Comparison of the trends of the specific entropy generation (J/K mol fuel) and entropy generation rate per unit molar flowrate of the air (J/K mol air) versus the compressor pressure ratio (TIT = 1200 K)

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