Comprehensive performance evaluation method of working fluids for high temperature heat pump based on multi-objective optimization

• Published in: Applied thermal engineering Vol. 247; p. 123102
• Main Authors: Xu, Chang, Ma, Hongting, Yu, Xiaohui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.06.2024
• Subjects: Comprehensive evaluation; High temperature heat pump; Multi-objective optimization; Working fluid; Multi-objective optimization; Comprehensive evaluation; Working fluid; High temperature heat pump
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2024.123102

•An efficient evaluation method for mixed refrigerants in HTHP is proposed.•Multi-objective optimization is used to evaluate the performance of refrigerants.•Various heat pump configurations are taken into account during evaluation process.•A distinction is made between dry and wet refrigerants in calculations. The working fluid has garnered significant attention as a critical factor influencing the efficiency of high-temperature heat pumps. A novel method based on multi-objective optimization has been introduced for assessing the performance of heat pump working fluids. The method enhances the clarity of the objective and flexibility in addressing various operating conditions, which helps to improve the efficiency of working fluid screening, especially for the complex mixture system. This study utilizes eight pure refrigerants as the initial fluid set and evaluates 560 binary mixtures with a 5% composition variation. The NSGA-II algorithm is combined with the theoretical heat pump cycle model to obtain Pareto optimal solutions regarding the mixtures, with the coefficient of performance and volumetric heating capacity as the objective functions. Then the evaluation of the optimal solutions is conducted by considering their flammability, toxicity, environmental performance, and temperature glide properties. Subsequently, a comprehensive performance index is derived. The evaluation reveals the dominant solution set for each pure refrigerant. The findings suggest that the blend R142b/R1233zd(E) with a mass fraction of R142b between 0.15 and 0.25 demonstrates a comprehensive performance index of 0.322–0.350, indicating superior performance during the basic cycle. Furthermore, various cycle configurations have been investigated. In the vapor injection configuration, R600a/R601(0.6/0.4) shows good performance in all aspects except flammability. The mixture R245fa/R601(0.2/0.8) exhibits superior overall performance in the internal heat exchanger configuration. It displays excellent temperature glide matching characteristics and good environmental performance. Nevertheless, it shows suboptimal performance in terms of toxicity and flammability. This approach replaces the previous qualitative comparison-based decision making methods, offering high efficiency and practicality.