The current paper studies the most suitable ultra-low-global warming potential (GWP) (GWP < 30) candidates in the market, considering also its grade of flammability and toxicity, for heat pumps employed for different space heating and domestic hot water (DHW) applications. A pre-design thermodynamic model has been developed to evaluate the performance and size limits for any subcritical or transcritical heat pump under certain working conditions. This generic model is based on the pinch point approach, so it does not depend on a certain type of heat exchangers, it only depends on the external working conditions. The results showed that all subcritical ultra-low-GWP, nonflammable, and nontoxic refrigerants considered have either lower coefficient of performance (COP) or volumetric heating capacity (VHC) compared with the reference high-GWP refrigerants R-410A and R-134a. Additionally, the only refrigerants with higher COP, such as R-717 (ammonia) or R-290 (propane), are either extremely flammable or toxic. For the applications need of high water-side temperature lift, the transcritical refrigerants R-744 (CO₂) and R-170 (ethane) showed the best performance, regarding both COP and VHC values, of all the refrigerants studied. The refrigerants R-161, R-1270 (propylene), and R-1234yf presented a balanced performance in both space heating and DHW applications. This makes them potential candidates to be employed in subcritical multi-temperature levels heat pumps.

中文翻译：

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用于空间和水加热器的超低全球升温潜能制冷剂的热力学评估

当前的论文研究了市场上最适合的超低全球变暖潜势（GWP <30）候选产品，同时考虑了其可燃性和毒性等级，适用于不同空间采暖和生活热水（DHW）的热泵）应用程序。已开发出一种预设计的热力学模型，以评估在某些工作条件下任何亚临界或跨临界热泵的性能和尺寸限制。该通用模型基于收缩点方法，因此它不取决于特定类型的热交换器，而仅取决于外部工作条件。结果表明，所有亚临界超低全球升温潜能值，不可燃，与参考的高GWP制冷剂R-410A和R-134a相比，所考虑的无毒制冷剂的性能系数（COP）或容积热容量（VHC）更低。此外，唯一具有较高COP的制冷剂，例如R-717（氨）或R-290（丙烷），极易燃或有毒。对于需要高水侧温度提升的应用，跨临界制冷剂R-744（CO₂）和R-170（乙烷）在所有研究的制冷剂中均表现出COP和VHC值最佳的性能。R-161，R-1270（丙烯）和R-1234yf制冷剂在空间供暖和DHW应用中均表现出平衡的性能。这使其成为潜在的候选材料，可用于亚临界多温度水平的热泵。