Thermo-Economic Analysis of Zeotropic Mixtures and Pure Working Fluids in Organic Rankine Cycles for Waste Heat Recovery

Florian Heberle and Dieter Brüggemann
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Florian Heberle: Institute of Engineering Thermodynamics (LTTT), Center of Energy Technology (ZET), University of Bayreuth, Bayreuth 95440, Germany
Dieter Brüggemann: Institute of Engineering Thermodynamics (LTTT), Center of Energy Technology (ZET), University of Bayreuth, Bayreuth 95440, Germany

Energies, 2016, vol. 9, issue 4, 1-16

Abstract: We present a thermo-economic analysis of an Organic Rankine Cycle (ORC) for waste heat recovery. A case study for a heat source temperature of 150 °C and a subcritical, saturated cycle is performed. As working fluids R245fa, isobutane, isopentane, and the mixture of isobutane and isopentane are considered. The minimal temperature difference in the evaporator and the condenser, as well as the mixture composition are chosen as variables in order to identify the most suitable working fluid in combination with optimal process parameters under thermo-economic criteria. In general, the results show that cost-effective systems have a high minimal temperature difference ?T PP,C at the pinch-point of the condenser and a low minimal temperature difference ?T PP,E at the pinch-point of the evaporator. Choosing isobutane as the working fluid leads to the lowest costs per unit exergy with 52.0 €/GJ ( ?T PP,E = 1.2 K; ?T PP,C = 14 K). Considering the major components of the ORC, specific costs range between 1150 €/kW and 2250 €/kW. For the zeotropic mixture, a mole fraction of 90% isobutane leads to the lowest specific costs per unit exergy. A further analysis of the ORC system using isobutane shows high sensitivity of the costs per unit exergy for the selected cost estimation methods and for the isentropic efficiency of the turbine.

Keywords: energy conversion systems; Organic Rankine Cycle (ORC); waste heat recovery; thermo-economic analysis; working fluids; zeotropic mixtures (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (24)

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