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Comparative Analysis of Transcritical CO 2 Heat Pump Systems With and Without Ejector: Performance, Exergy, and Economic Perspective

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  • Xiang Qin

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China
    Environmental System Research Laboratory, Faculty of Engineering, Hokkaido University, N13-W8, Sapporo 060-8628, Japan)

  • Shihao Lei

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

  • Heyu Liu

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

  • Yinghao Zeng

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

  • Yajun Liu

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

  • Caiyan Pang

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

  • Jiaheng Chen

    (School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China)

Abstract

To promote renewable energy utilization and enhance the environmental friendliness of refrigerants, this study presents a novel experimental investigation on a transcritical CO 2 double-evaporator heat pump water heater integrating both air and water sources, designed for high-temperature hot water production. A key innovation of this work lies in the integration of an ejector into the dual-source system, aiming to improve system performance and energy efficiency. This study systematically compares the conventional circulation mode and the proposed ejector-assisted circulation mode in terms of system performance, exergy efficiency, and the economic payback period. Experimental results reveal that the ejector-assisted mode not only achieves a higher water outlet temperature and reduces compressor power consumption but also improves the system’s exergy efficiency by 6.6% under the condition of the maximum outlet water temperature. Although the addition of the ejector increases initial manufacturing and maintenance costs, the payback periods of the two modes remain nearly the same. These findings confirm the feasibility and advantage of incorporating an ejector into a transcritical CO 2 compression/ejection heat pump system with integrated air and water sources, offering a promising solution for efficient and environmentally friendly high-temperature water heating applications.

Suggested Citation

  • Xiang Qin & Shihao Lei & Heyu Liu & Yinghao Zeng & Yajun Liu & Caiyan Pang & Jiaheng Chen, 2025. "Comparative Analysis of Transcritical CO 2 Heat Pump Systems With and Without Ejector: Performance, Exergy, and Economic Perspective," Energies, MDPI, vol. 18(12), pages 1-20, June.
    • Handle: RePEc:gam:jeners:v:18:y:2025:i:12:p:3223-:d:1683033
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    References listed on IDEAS

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    1. Qin, Xiang & Wang, Dingbiao & Jin, Zunlong & Wang, Junlei & Zhang, Guojie & Li, Hang, 2021. "A comprehensive investigation on the effect of internal heat exchanger based on a novel evaluation method in the transcritical CO2 heat pump system," Renewable Energy, Elsevier, vol. 178(C), pages 574-586.
    2. Chen, Xiangjie & Worall, Mark & Omer, Siddig & Su, Yuehong & Riffat, Saffa, 2013. "Theoretical studies of a hybrid ejector CO2 compression cooling system for vehicles and preliminary experimental investigations of an ejector cycle," Applied Energy, Elsevier, vol. 102(C), pages 931-942.
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