Exergy efficiency potential of dual-phase expansion trilateral and partial evaporation ORC with zeotropic mixtures

Konstantinos Braimakis and Sotirios Karellas

Energy, 2023, vol. 262, issue PB

Abstract: The exergy efficiency improvement potential of dual-phase expansion (trilateral and partial evaporation) Organic Rankine Cycles (ORC) with zeotropic mixtures of R1233zd(E), R1234ze(E) and R1234yf as well as isobutane and propane for waste heat temperatures from 80 °C to 200 °C is investigated. For each fluid pair, standard ORCs are compared to trilateral and partial evaporation cycles (T-ORC and P-ORC) of mixtures (T-Z and PE-Z) and pure fluids. For isobutane-propane and R1233zd(E)-R1234ze(E), PE-Z and T-Z cycles result in the highest exergy efficiency for most temperatures. For R1233zd(E)-R1234yf, PE-Z and T-Z cycles are superior below 140 °C. For R1234ze(E)-R1234yf, PE-ORCs and standard ORCs with R1234ze(E) are most efficient at temperatures below and above 140 °C, respectively. PE-Z cycles of R1233zd(E)-R1234ze(E) exhibit the highest efficiency at all temperatures except for 100 °C, at which T-Z cycles are superior. Generally, PE-Z cycles have slightly higher exergy efficiency compared to PE-ORCs with pure fluids of high critical temperature. Given the technical challenges of zeotropic cycles, the latter could be more appealing. For expansion isentropic efficiencies around 60%, dual-phase expansion cycles remain competitive against saturated vapor zeotropic (S-Z) and saturated ORCs at lower temperatures. However, isentropic efficiencies above 50% are necessary for them to be competitive against S-Z cycles.

Keywords: ORC; Exergy efficiency; Dual-phase expansion; Partial evaporation; Trilateral; Flash; TFC; Zeotropic; Zeotropic mixture; Optimization (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (9)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:262:y:2023:i:pb:s036054422202357x

DOI: 10.1016/j.energy.2022.125475

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