Parametric Study of a Supercritical CO 2 Power Cycle for Waste Heat Recovery with Variation in Cold Temperature and Heat Source Temperature

Young-Min Kim, Young-Duk Lee and Kook-Young Ahn
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Young-Min Kim: Research Division of Environmental and Energy Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34104, Korea
Young-Duk Lee: Department of Energy Technology, Korea Institute of Energy Technology (KENTECH), 200 Hyuksin-ro, Naju 58330, Korea
Kook-Young Ahn: Research Division of Environmental and Energy Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34104, Korea

Energies, 2021, vol. 14, issue 20, 1-12

Abstract: The supercritical carbon dioxide (S-CO 2 ) power cycle is a promising development for waste heat recovery (WHR) due to its high efficiency despite its simplicity and compactness compared with a steam bottoming cycle. A simple recuperated S-CO 2 power cycle cannot fully utilize the waste heat due to the trade-off between the heat recovery and thermal efficiency of the cycle. A split cycle in which the working fluid is preheated by the recuperator and the heat source separately can be used to maximize the power output from a given waste heat source. In this study, the operating conditions of split S-CO 2 power cycles for waste heat recovery from a gas turbine and an engine were studied to accommodate the temperature variation of the heat sink and the waste heat source. The results show that it is vital to increase the low pressure of the cycle along with a corresponding increase in the cooling temperature to maintain the low-compression work near the critical point. The net power decreases by 6 to 9% for every 5 °C rise in the cooling temperature from 20 to 50 °C due to the decrease in heat recovery and thermal efficiency of the cycle. The effect of the heat-source temperature on the optimal low-pressure side was negligible, and the optimal high pressure of the cycle increased with an increase in the heat-source temperature. As the heat-source temperature increased in steps of 50 °C from 300 to 400 °C, the system efficiency increased by approximately 2% (absolute efficiency), and the net power significantly increased by 30 to 40%.

Keywords: supercritical CO 2 (S-CO 2 ) power cycle; waste heat recovery; exhaust gas; cold temperature; split cycle (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: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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