Experimental Energy and Exergy Performance Evaluation of a Novel Pumpless Rankine Cycle (PRC) Unit Employing Low-Temperature Heat Sources

Evangelos Syngounas (), John Konstantaras, Nikolaos Arapkoules, Dimitrios Tsimpoukis, Maria K. Koukou () and Michail Gr. Vrachopoulos
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Evangelos Syngounas: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece
John Konstantaras: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece
Nikolaos Arapkoules: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece
Dimitrios Tsimpoukis: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece
Maria K. Koukou: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece
Michail Gr. Vrachopoulos: Energy and Environmental Research Laboratory, Department of Agricultural Development, Agri-Food and Natural Resources Management, National and Kapodistrian University of Athens, 34000 Psachna, Evia, Greece

Energies, 2025, vol. 18, issue 17, 1-25

Abstract: The current study experimentally investigates the performance of a novel pumpless Rankine cycle (PRC) configuration utilizing low-temperature heat sources. Precisely, a 1 kW e PRC configuration using R245fa refrigerant is tested under different heat source and heat sink temperature levels. The energetic and exergetic performance indexes are calculated using validated simulation models developed in MATLAB incorporating the CoolProp library. The derived efficiency results are compared with the corresponding indexes of a conventional ORC system used as the baseline. The findings show that for a hot water heat source temperature of 90 °C and a cold water heat sink temperature of 10 °C as the working conditions, the time-averaged thermal efficiency maximizes at 4.5%, while the corresponding time-averaged exergy efficiency is calculated at 31%. Additionally, the innovative PRC topology shows higher efficiency rates compared to the conventional ORC solution for all the working scenarios tested. For a heat sink of 40 °C and a heat source of 90 °C, the thermal efficiency and the exergy efficiency calculated for the PRC are 7.7% and 7.5% higher, respectively, than the baseline ORC system, showing improved exploitation potential.

Keywords: pumpless Rankine cycle; sustainable power generation; low-temperature heat source renewables; energy efficiency; exergy efficiency (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: 2025
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