Improving the thermodynamic efficiency and turboexpander design in bottoming organic Rankine cycles: The impact of working fluid selection

Zvonimir Guzović, Simun Kastrapeli, Marina Budanko, Mario Klun and Predrag Rašković

Energy, 2024, vol. 307, issue C

Abstract: In the contemporary context, significant importance is attributed to micro and small-scale Organic Rankine Cycle (ORC) units that are specifically designed for decentralized electricity generation. An essential component within each ORC system is the expander, available in both volumetric and turboexpander configurations. In the existing biogas plant with an Internal Combustion Engine (ICE), the ORC, functioning as a bottoming cycle (BORC) on ICE waste heat, is installed. The BORC utilizes the heat from exhaust gases and the cooling water of the ICE. The paper investigates the effects of various working fluids on both the thermodynamic efficiency of the BORC and the isentropic efficiency of the turboexpander, thus influencing the design parameters of the turboexpander (e.g., number of stages, stator and rotor blade heights, etc.). The BORC, employing the working fluid R141b, has exhibited superior thermodynamic performance, demonstrating a commendable 63.5 kW in net power with a thermodynamic efficiency of 13 %, and ultimately increased the power of the ICE (537 kW) by approx. 12 %. Regarding the turbine component, the turbine operating with the R141b working fluid demonstrated the highest power output and isentropic efficiency, achieving values of 64.14 kW and 67.4 %, respectively. A design was developed for the same turbine, with aerodynamically perfect profiles specially designed for the stator and rotor blades.

Keywords: Bottoming organic Rankine cycle (BORC); Turboexpander design; Working fluid influence; Internal combustion engine (ICE); Waste heat; New turbine design (search for similar items in EconPapers)
Date: 2024
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Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:307:y:2024:i:c:s0360544224024162

DOI: 10.1016/j.energy.2024.132642

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