Investigation on the use of a novel regenerative flow turbine in a micro-scale Organic Rankine Cycle unit

• Published in: Energy (Oxford) Vol. 210; p. 118519
• Main Authors: Moradi, Ramin, Habib, Emanuele, Bocci, Enrico, Cioccolanti, Luca
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2020; Elsevier BV
• Subjects: CFD simulation; Competitiveness; Computational fluid dynamics; Expanders; Flow rates; Heat; Heat recovery; Heat sources; Investigations; Low cost; Low temperature; Low-grade waste heat recovery; Mass flow rate; Mathematical models; Micro combined heat and power system; Numerical models; Rankine cycle; Regenerative flow turbine; Small-scale ORC; Three dimensional models; Turbines; Waste heat recovery; Working fluids; CFD simulation; Small-scale ORC; Micro combined heat and power system; Regenerative flow turbine; Low-grade waste heat recovery
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2020.118519

Reliable and low-cost expanders are fundamental for the competitiveness of small-scale Organic Rankine Cycle (ORC) plants using low-temperature heat sources. Regenerative flow turbines (RFTs) can be considered a low-cost and viable alternative expander, yet their performance needs to be fully investigated. Therefore, the use of an RFT in a micro-scale ORC test bench is investigated in this work through a modelling study. Specifically, three-dimensional CFD simulations are carried out to assess the performance of the considered expander with varying operating conditions and a numerical model of a non-regenerative, small-scale ORC system is developed to investigate its potential in waste heat recovery (WHR) applications. Using R245fa as the working fluid, the CFD analysis shows that the expander achieves a maximum total-to-static isentropic efficiency of about 44% in the investigated operating range. The small-scale ORC system has a net output power in the range 100–600 W and a net cycle efficiency of 1–2.3%. Moreover, a comparison with two scroll expanders having different built-in volume ratios shows that the RFT operates with higher isentropic efficiencies in low mass flow rates and pressure ratios thus highlighting its suitability for low-temperature WHR applications, especially when considerable fluctuations of the heat source are expected. •Characteristics of an RFT working with R245fa is presented using CFD simulation.•A micro-scale ORC unit with RFT is simulated in low pressure ratios.•Performance of the RFT is compared with those of two scroll expanders with different BVRs.•RTF shows higher performance in low pressure ratios compared to scroll expanders.•RFTs can be introduced as alternative technology for low-temperature WHR applications.