用于低温环境的复叠式空气源热泵热水机组系统性能研究*
摘要：
传统的空气源热泵难以在低环境温度的亚寒带地区制备高温热水,环境温度为-30 ℃时单级空气源热泵的制热性能显著衰减,难以维持有效的制热循环。为解决这个问题,本研究构建了一种复叠式空气源热泵热水系统热力学分析模型,实现了在-30 ℃低温环境下制备80 ℃高温热水,可以用于严寒地区供热。本文选取4种高温级制冷剂(R134a、R407C、R236ea和R1234ze(Z))与低温级制冷剂(R32)组成制冷剂对,对比研究了系统制热COP、压缩机参数、系统损失和效率。结果显示,在环境温度为-30 ℃时,R1234ze(Z)/R32制冷剂对的系统制热效果最好。还研究了环境温度从-30 ℃升高到30 ℃时该复叠式空气源热泵热水机组的COP最大值、最佳中间温度、最佳质量流量比、压缩机参数、损失和效率的变化,分析了其与环境温度的关系。
Abstract：
It is difficult for conventional air-source heat pumps (ASHP) to produce high-temperature hot water in subarctic regions with low ambient temperatures. When the ambient temperature is -30 ℃, the heating performance of a single-stage ASHP is significantly attenuated, making it difficult to maintain an effective heating cycle. In order to solve this problem, a thermodynamic analysis model is developed for a cascade ASHP water heating system capable of producing 80 ℃ high-temperature hot water in a -30 ℃ low-temperature environment, which can be used for heating in the severe cold zone. In this paper, four high-temperature stage refrigerants (R134a, R407C, R236ea and R1234ze (Z)) are each paired with a low-temperature stage refrigerant (R32), and they are compared using performance metrics including the heating COP, compressor parameters, exergy losses and exergy efficiency of the system. The results show that when the ambient temperature is -30 ℃, the system with R1234ze (Z)/R32 refrigerant combination has the best heating effect. The changes in the maximum COP value, optimal intermediate temperature, optimal mass flow ratio, compressor parameters, exergy losses and exergy efficiency of the cascade ASHP water heater are also studied when the ambient temperature increases from -30 ℃ to 30 ℃, and their relationships with the ambient temperature are analysed.
Keywords:air-source heat pump; cascade system; low-temperature environment; exergy analysis; performance analysis; refrigerant; compressor