Energy Analysis of Waste Heat Recovery Using Supercritical CO 2 Brayton Cycle for Series Hybrid Electric Vehicles

Gabriel Mocanu, Cristian Iosifescu, Ion V. Ion (), Florin Popescu, Michael Frătița and Robert Mădălin Chivu
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Gabriel Mocanu: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania
Cristian Iosifescu: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania
Ion V. Ion: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania
Florin Popescu: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania
Michael Frătița: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania
Robert Mădălin Chivu: Thermal System and Automotive Department, “Dunărea de Jos” Universitaty of Galați, 800008 Galati, Romania

Energies, 2024, vol. 17, issue 11, 1-17

Abstract: Waste heat recovery from exhaust gas is one of the most convenient methods to save energy in internal combustion engine-driven vehicles. This paper aims to investigate a reduction in waste heat from the exhaust gas of an internal combustion engine of a serial Diesel–electric hybrid bus by recovering part of the heat and converting it into useful power with the help of a split-flow supercritical CO 2 (sCO 2 ) recompression Brayton cycle. It can recover 17.01 kW of the total 33.47 kW of waste heat contained in exhaust gas from a 151 kW internal combustion engine. The thermal efficiency of the cycle is 38.51%, and the net power of the cycle is 6.55 kW. The variation in the sCO 2 temperature at the shutdown of the internal combustion engine is analyzed, and a slow drop followed by a sudden and then a slow drop is observed. After 80 s from stopping the engine, the temperature drops by (23–33)% depending on the tube thickness of the recovery heat exchanger. The performances (net power, thermal efficiency, and waste heat recovery efficiency) of the split-flow sCO 2 recompression Brayton cycle are clearly superior to those of the steam Rankine cycle and the organic Rankine cycle (ORC) with cyclopentane as a working fluid.

Keywords: internal combustion engine; waste heat; supercritical CO 2 recompression Brayton cycle; heat recovery (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: 2024
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