Title: Novel pinch point method based exergetic optimisation of subcritical organic Rankine cycle for waste heat recovery

Authors: Jahar Sarkar

Addresses: Department of Mechanical Engineering, Indian Institute of Technology, (BHU) Varanasi, 221005, India

Abstract: A new pinch point design methodology for subcritical organic Rankine cycle (ORC) is proposed to predict pinch point locations in both evaporator and condenser, and optimise working fluid mass flow rate to get maximum heat recovery and exergetic efficiency for given heat source and heat sink conditions. Selected working fluids have been compared based on different performance parameters for various heat source conditions. The present method seems to be better than previous pinch point design methods as it optimises the cycle by considering both source and sink. At optimum operation, ammonia is best in terms of lower mass flow rate and turbine size, toluene is best in terms of lowest heat exchanger size and cost, whereas, R-1233zd and isopentane are best in terms of higher power output and heat recovery, exergy and entrancy efficiencies. Contour plots are presented as well to select optimum design parameters for available heat source and sink.

Keywords: waste heat recovery; ORC; organic Rankine cycle; pinch point temperature difference; exergetic efficiency; irreversibility; entrancy efficiency.

DOI: 10.1504/IJEX.2018.091551

International Journal of Exergy, 2018 Vol.25 No.4, pp.281 - 299

Received: 04 Jul 2017
Accepted: 31 Oct 2017
Published online: 04 May 2018 *

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