Optimization of Cycle and Expander Design of an Organic Rankine Cycle Unit using Multi-Component Working Fluids

Andrea Meroni, Jesper Graa Andreasen, Leonardo Pierobon, Fredrik Haglind

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

Organic Rankine cycle (ORC) power systems represent at-tractive solutions for power conversion from low temperatureheat sources, and the use of these power systems is gaining increasing attention in the marine industry. This paper proposesthe combined optimal design of cycle and expander for an organic Rankine cycle unit utilizing waste heat from low temperature heat sources. The study addresses a case where the minimum temperature of the heat source is constrained and a case where no constraint is imposed. The former case is the wasteheat recovery from jacket cooling water of a marine diesel engine onboard a large ship, and the latter is representative of a low-temperature geothermal, solar or waste heat recovery application. Multi-component working fluids are investigated, as they allow improving the match between the temperature pro-files in the heat exchangers and, consequently, reducing the irreversibility in the ORC system. This work considers mixtures of R245fa/pentane and propane/isobutane. The use of multi-component working fluids typically results in increased heat transfer areas and different expander designs compared to purefluids. In order to properly account for turbine performance and design constraints in the cycle calculation, the thermodynamic cycle and the turbine are optimized simultaneously in the molarcomposition range of each mixture. Such novel optimization approach enables one to identify to which extent the cycle or the turbine behaviour influences the selection of the optimal solution. It also enables one to find the composition for which an optimal compromise between cycle and turbine performance is achieved.The optimal ORC unit employs pure R245fa and provides approximately 200 kW when the minimum hot fluid temperature is constrained. Conversely, the mixture R245fa/pentane (0.5/0.5) is selected and provides approximately 444 kW when the hot fluid temperature is not constrained to a lower value. In both cases, acompact and efficient turbine can be manufactured.
Original languageEnglish
Title of host publicationProceedings of ASME Turbo Expo 2016
Number of pages12
PublisherAmerican Society of Mechanical Engineers
Publication date2016
Article numberGT2016-58065
ISBN (Electronic)978-0-7918-4974-3
DOIs
Publication statusPublished - 2016
EventASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition GT2016 - Seoul, Korea, Republic of
Duration: 13 Jun 201617 Jun 2016

Conference

ConferenceASME Turbo Expo 2016
CountryKorea, Republic of
CitySeoul
Period13/06/201617/06/2016

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