From organic rankine cycles to high-temperature heat pumps : A thermo-economic investigation of potential working fluids

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Obika, Echezona ; Heberle, Florian ; Brüggemann, Dieter:
From organic rankine cycles to high-temperature heat pumps : A thermo-economic investigation of potential working fluids.
In: Energy Conversion and Management: X. Bd. 27 (2025) . - 101156.
ISSN 2590-1745
DOI: https://doi.org/10.1016/j.ecmx.2025.101156

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Abstract

The thermo-economic performance of high-temperature heat pump utilizing working fluids applied to ORC systems with high critical temperatures like cyclohexane, hexane and cyclopentane were compared to intensively examined working fluids, in this study. The aim is to determine their economic feasibility for high temperature supply up to 150 °C. The vapor compression cycle with internal heat exchanger was adopted for this evaluation, for a heat source of 50 °C, supply temperatures in the range of 100 to 150oC and heat exchanger pinch point temperature difference of 5 K. The coefficient of performance (COP) of the cycle was optimized at the considered boundary condition by attaining maximum subcooling at the condenser. A 7.9 higher COP was obtained with cyclopentane compared to the state-of-the-art working fluid R1336mzz(Z). From the economic point of view these cyclic hydrocarbons, especially cyclopentane, are associated with 1.5 higher specific investment cost. However, these working fluids lead to 5 discounted payback period due to increased performance, compared to R1336mzz(Z). These positive results affirm the prospect of cyclopentane as a suitable working fluid for heat pump applications both from the thermodynamic and economic point of view.