The Collaborative Optimization of the Discharge Pressure and Heat Recovery Rate in a Transcritical CO 2 Heat Pump Used in Extremely Low Temperature Environment

Zhongkai Wu, Feifei Bi, Jiyou Fei, Zecan Zheng, Yulong Song () and Feng Cao
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Zhongkai Wu: Collage of Locomotive and Rolling Stock Engineering, Dalian Jiaotong University, Dalian 116024, China
Feifei Bi: Collage of Locomotive and Rolling Stock Engineering, Dalian Jiaotong University, Dalian 116024, China
Jiyou Fei: Collage of Locomotive and Rolling Stock Engineering, Dalian Jiaotong University, Dalian 116024, China
Zecan Zheng: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Yulong Song: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Feng Cao: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Energies, 2023, vol. 16, issue 4, 1-16

Abstract: Considering the excellent environmental properties and heating capability under wide running conditions of the natural fluid CO 2 , the transcritical CO 2 heat pump system has widely been used in the application of water heaters, commercial heating and cooling, electric vehicle thermal management, etc. Since the performance was highly affected by the discharge pressure and heat recovery rate in a transcritical CO 2 system, the collaborative optimization of these two parameters was analyzed in detail in this study. The results showed that the optimal value of the system heating COP, which was the ration of heating capacity to power consumption, was better under a higher heat recovery rate and relatively lower discharge pressure, which is why these kinds of operating conditions are highly recommended from the perspective of collaborative optimization. Additionally, the heat recovery rate had a positive effect on the system performance when the discharge pressure was lower than its optimal value, while the heat recovery rate would present a passive effect on the system performance when the discharge pressure was higher than its optimal value. The relevant conclusions of this study provide a good theoretical basis for the efficient and stable operation of the transcritical CO 2 heat pump technology under the conditions of a wide ambient temperature range.

Keywords: transcritical CO 2 heat pump; collaborative optimization; optimal discharge pressure; optimal heat recovery rate (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: 2023
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