Study on CO2 zeotropic mixture heat pump for waste heat deep recovery - Energy and exergy analysis

Tao Zhang, Yumiao Wang, Jian Liu, Jianhong Cheng and Xiaosong Zhang

Energy, 2025, vol. 329, issue C

Abstract: Applying heat pumps for waste heat recovery has gained significant attention. Zeotropic mixtures can significantly improve the coefficient of performance (COP) by optimizing temperature matching. This study validates the superiority of zeotropic mixtures in waste heat deep recovery and explores their COP enhancement mechanisms. The CO2/R290 and CO2/R1234yf mixtures were analyzed through simulation and experimental investigation. The experimental results demonstrate that under standard operating condition, both CO2/R290 and CO2/R1234yf achieved their maximum COP at a CO2 mass fraction of 15 %. Compared to pure R290, these mixtures demonstrated COP improvements of 75.2 % and 27.7 %, respectively. Exergy analysis of the experimental results revealed that, the CO2 mass fraction primarily affects the compression and expansion exergetic efficiencies via pressure ratio. It also affects the evaporator's and condenser's exergetic efficiencies through glide temperature. Both simulation and experimental results confirm that zeotropic mixtures exhibit progressively greater performance advantages over pure refrigerants as waste heat recovery ratios increase. While the heat sink outlet temperature in this study remains relatively low (45 °C), the performance enhancement mechanisms of zeotropic mixtures and the functional mechanisms of CO2 mass fraction revealed by this research can provide theoretical guidance for the development of higher-temperature zeotropic mixture heat pump systems.

Keywords: Waste heat deep recovery; Zeotropic mixture; Glide temperature; Exergy analysis (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:329:y:2025:i:c:s0360544225023047

DOI: 10.1016/j.energy.2025.136662

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