LAPSE:2018.1144v1
Published Article
LAPSE:2018.1144v1
Thermo-Economic and Heat Transfer Optimization of Working-Fluid Mixtures in a Low-Temperature Organic Rankine Cycle System
November 28, 2018
In the present paper, we consider the employment of working-fluid mixtures in organic Rankine cycle (ORC) systems with respect to thermodynamic and heat-transfer performance, component sizing and capital costs. The selected working-fluid mixtures promise reduced exergy losses due to their non-isothermal phase-change behaviour, and thus improved cycle efficiencies and power outputs over their respective pure-fluid components. A multi-objective cost-power optimization of a specific low-temperature ORC system (operating with geothermal water at 98 °C) reveals that the use of working-fluid-mixtures does indeed show a thermodynamic improvement over the pure-fluids. At the same time, heat transfer and cost analyses, however, suggest that it also requires larger evaporators, condensers and expanders; thus, the resulting ORC systems are also associated with higher costs. In particular, 50% n-pentane + 50% n-hexane and 60% R-245fa + 40% R-227ea mixtures lead to the thermodynamically optimal cycles, whereas pure n-pentane and pure R-245fa have lower plant costs, both estimated as having ∼14% lower costs per unit power output compared to the thermodynamically optimal mixtures. These conclusions highlight the importance of using system cost minimization as a design objective for ORC plants.
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Keywords
heat transfer coefficients, low-grade heat, low-pressure expanders, multi-objective optimization, ORC capital costs, organic Rankine cycles (ORC), thermo-economic analysis, working-fluid mixtures
Subject
Suggested Citation
Oyewunmi OA, Markides CN. Thermo-Economic and Heat Transfer Optimization of Working-Fluid Mixtures in a Low-Temperature Organic Rankine Cycle System. (2018). LAPSE:2018.1144v1
Author Affiliations
Oyewunmi OA: Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
Markides CN: Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK [ORCID]
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Markides CN: Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK [ORCID]
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Journal Name
Energies
Volume
9
Issue
6
Article Number
E448
Year
2016
Publication Date
2016-06-09
Published Version
ISSN
1996-1073
Version Comments
Original Submission
Other Meta
PII: en9060448, Publication Type: Journal Article
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Published Article
LAPSE:2018.1144v1
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External Link
doi:10.3390/en9060448
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[v1] (Original Submission)
Nov 28, 2018
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Nov 28, 2018
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v1
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https://psecommunity.org/LAPSE:2018.1144v1
Original Submitter
Calvin Tsay
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