Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles
The increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., us...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-01-01
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| Series: | Energies |
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| Online Access: | https://www.mdpi.com/1996-1073/14/2/307 |
| _version_ | 1797414788241817600 |
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| author | Aram Mohammed Ahmed László Kondor Attila R. Imre |
| author_facet | Aram Mohammed Ahmed László Kondor Attila R. Imre |
| author_sort | Aram Mohammed Ahmed |
| collection | DOAJ |
| description | The increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., using an added high-temperature heat source to the existing low-temperature heat source. Obviously, this kind of improvement has technical difficulties and added costs; therefore, the increase of efficiency by increasing the maximal temperature sometimes has technical and/or financial limits. In this paper, we would like to show that for an ideal, simple-layout ORC system, a thermodynamic efficiency-maximum can also exist. It means that for several working fluids, the thermodynamic efficiency vs. maximal cycle temperature function has a maximum, located in the sub-critical temperature range. A proof will be given by comparing ORC efficiencies with TFC (Trilateral Flash Cycle) efficiencies; for wet working fluids, further theoretical evidence can be given. The group of working fluids with this kind of maximum will be defined. Generalization for normal (steam) Rankine cycles and CO<sub>2</sub> subcritical Rankine cycles will also be shown. Based on these results, one can conclude that the increase of the maximal cycle temperature is not always a useful tool for efficiency-increase; this result can be especially important for hybrid systems. |
| first_indexed | 2024-03-09T05:38:53Z |
| format | Article |
| id | doaj.art-47cbb5806ffc4a289eb1f65dcf8c2883 |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-09T05:38:53Z |
| publishDate | 2021-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-47cbb5806ffc4a289eb1f65dcf8c28832023-12-03T12:26:46ZengMDPI AGEnergies1996-10732021-01-0114230710.3390/en14020307Thermodynamic Efficiency Maximum of Simple Organic Rankine CyclesAram Mohammed Ahmed0László Kondor1Attila R. Imre2Department of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, HungaryDepartment of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, HungaryDepartment of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, HungaryThe increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., using an added high-temperature heat source to the existing low-temperature heat source. Obviously, this kind of improvement has technical difficulties and added costs; therefore, the increase of efficiency by increasing the maximal temperature sometimes has technical and/or financial limits. In this paper, we would like to show that for an ideal, simple-layout ORC system, a thermodynamic efficiency-maximum can also exist. It means that for several working fluids, the thermodynamic efficiency vs. maximal cycle temperature function has a maximum, located in the sub-critical temperature range. A proof will be given by comparing ORC efficiencies with TFC (Trilateral Flash Cycle) efficiencies; for wet working fluids, further theoretical evidence can be given. The group of working fluids with this kind of maximum will be defined. Generalization for normal (steam) Rankine cycles and CO<sub>2</sub> subcritical Rankine cycles will also be shown. Based on these results, one can conclude that the increase of the maximal cycle temperature is not always a useful tool for efficiency-increase; this result can be especially important for hybrid systems.https://www.mdpi.com/1996-1073/14/2/307ORCTrilateral Flash Cycle<i>T-s</i> diagramadiabatic expansionworking fluidretrofit |
| spellingShingle | Aram Mohammed Ahmed László Kondor Attila R. Imre Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles Energies ORC Trilateral Flash Cycle <i>T-s</i> diagram adiabatic expansion working fluid retrofit |
| title | Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles |
| title_full | Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles |
| title_fullStr | Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles |
| title_full_unstemmed | Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles |
| title_short | Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles |
| title_sort | thermodynamic efficiency maximum of simple organic rankine cycles |
| topic | ORC Trilateral Flash Cycle <i>T-s</i> diagram adiabatic expansion working fluid retrofit |
| url | https://www.mdpi.com/1996-1073/14/2/307 |
| work_keys_str_mv | AT arammohammedahmed thermodynamicefficiencymaximumofsimpleorganicrankinecycles AT laszlokondor thermodynamicefficiencymaximumofsimpleorganicrankinecycles AT attilarimre thermodynamicefficiencymaximumofsimpleorganicrankinecycles |