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Entropy 2018, 20(11), 818; https://doi.org/10.3390/e20110818

Entropy and Entransy Dissipation Analysis of a Basic Organic Rankine Cycles (ORCs) to Recover Low-Grade Waste Heat Using Mixture Working Fluids

1
School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
2
Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, Tianjin University, Ministry of Education of China, Tianjin 300072, China
*
Authors to whom correspondence should be addressed.
Received: 16 September 2018 / Revised: 19 October 2018 / Accepted: 19 October 2018 / Published: 24 October 2018
(This article belongs to the Special Issue Entropy Generation and Heat Transfer)
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Abstract

Mixture working fluids can reduce effectively energy loss at heat sources and heat sinks, and therefore enhance the organic Rankine cycle (ORC) performance. The entropy and entransy dissipation analyses of a basic ORC system to recover low-grade waste heat using three mixture working fluids (R245fa/R227ea, R245fa/R152a and R245fa/pentane) have been investigated in this study. The basic ORC includes four components: an expander, a condenser, a pump and an evaporator. The heat source temperature is 120 °C while the condenser temperature is 20 °C. The effects of four operating parameters (evaporator outlet temperature, condenser temperature, pinch point temperature difference, degree of superheat), as well as the mass fraction, on entransy dissipation and entropy generation were examined. Results demonstrated that the entransy dissipation is insensitive to the mass fraction of R245fa. The entropy generation distributions at the evaporator for R245/pentane, R245fa/R152a and R245fa/R227ea are in ranges of 66–74%, 68–80% and 66–75%, respectively, with the corresponding entropy generation at the condenser ranges of 13–21%, 4–17% and 11–21%, respectively, while those at the expander for R245/pentane, R245fa/R152a and R245fa/R227ea are approaching 13%, 15% and 14%, respectively. The optimal mass fraction of R245fa for the minimum entropy generation is 0.6 using R245fa/R152a. View Full-Text
Keywords: organic Rankine cycles (ORCs); entropy; entransy dissipation; mixture working fluids organic Rankine cycles (ORCs); entropy; entransy dissipation; mixture working fluids
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Feng, Y.-Q.; Luo, Q.-H.; Wang, Q.; Wang, S.; He, Z.-X.; Zhang, W.; Wang, X.; An, Q.-S. Entropy and Entransy Dissipation Analysis of a Basic Organic Rankine Cycles (ORCs) to Recover Low-Grade Waste Heat Using Mixture Working Fluids. Entropy 2018, 20, 818.

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