Impact of the Lubricant on a Modified Revolving Vane Expander (M-RVE) in an Organic Rankine Cycle System

Ali Naseri, Ramin Moradi, Luca Cioccolanti () and Alison Subiantoro
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Ali Naseri: Department of Mechanical and Mechatronics Engineering, Faculty of Engineering, The University of Auckland, Auckland 1010, New Zealand
Ramin Moradi: Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XL, UK
Luca Cioccolanti: Research Centre for Energy, Environment and Landscape, Università eCampus, Via Isimbardi 10, 22060 Novedrate, Italy
Alison Subiantoro: Department of Mechanical and Mechatronics Engineering, Faculty of Engineering, The University of Auckland, Auckland 1010, New Zealand

Energies, 2023, vol. 16, issue 14, 1-17

Abstract: The expansion device is the critical component of micro-to-small scale organic Rankine cycle (ORC) systems, substantially affecting system efficiency and cost. Low isentropic efficiency and lubrication requirements are the main issues associated with using volumetric expanders in ORC systems. Despite lubrication contributing to reducing internal leakages in an expander, it may compromise the performance of the ORC system by adversely affecting the evaporator’s thermal capacity. This study tests a recently developed and modified revolving vane expander (M-RVE) in a micro-scale ORC test rig by implementing an adjustable oil mass flow rate. The impact of the lubricant oil on the performance of the M-RVE prototype is investigated within a wide range of oil circulation rates ( OCR ). The results demonstrate a negligible improvement in the filling factor for OCR s higher than 1%. Moreover, the shaft power is not considerably sensitive to OCR , while the calculated isentropic efficiency of the expander improves with OCR . Furthermore, the impact of the lubricant oil on the performance of the evaporator is studied, assuming the exact OCR as the expander and measured temperature and pressure similar to the pure refrigerant for the lubricant-refrigerant mixture in the evaporator. The study shows that the evaporator capacity is penalized with OCR , especially for values higher than 1%. Hence, an OCR of about 1% is a good compromise, and it can be used as a guideline for designing revolving vane expanders for micro-scale ORC systems without a dedicated lubricant oil circuit.

Keywords: expander lubrication; revolving vane expander; lubricant-refrigerant mixture; oil entrainment (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: 2023
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