Heating performance of recuperative heat pump using low-GWP mixed refrigerant

doi:10.11949/0438-1157.20201500

Abstract

Abstract:

With the implementation of the coal-to-electricity policy of China, efficient and eco-friendly heating methods are demanded for heating in northern China in winter. Air source heat pump is paid more attentions in recent years as a promising heating method, in which its efficiency under low ambient temperatures is urgent to be improved. In this paper, eco-friendly mixed refrigerant (CO₂ and 2,2-difluoropropane) is applied in a recuperative heat pump with simple structure, low cost and easy control, whose heating performances under different ambient temperatures are analyzed through theoretical optimization. When ambient temperature varies from -30℃ to 10℃, its COP varies from 1.87 to 3.51 while its volumetric heating capacity varies from 1773 kJ/m³ to 5516 kJ/m³. Through the comparison with common vapor-injection cycle, the potential and feasibility of the proposed heat pump cycle and refrigerant for winter heating are demonstrated. Besides, the excessive high operating pressure of regular CO₂ systems is well reduced due to the addition of 2,2-difluoropropane, which is beneficial for practical applications.

Key words: eco-friendly mixed refrigerant, recuperative heat pump, heating performance, theoretical investigation

摘要：

随着我国煤改电政策的逐步推行，我国北方地区的冬季采暖面临着环保高效的改进需求，空气源热泵作为近年来研究的热点，其低环温运行的效率值得关注。利用环保混合工质CO₂和2,2-二氟丙烷，本研究构建了结构简单、成本低廉且易于控制的回热热泵循环，并通过理论优化分析了该循环不同环境温度下的制热性能。当环境温度从-30℃变动至10℃，回热热泵循环的COP从1.87升高至3.51，单位容积制热量从1773 kJ/m³升高至5516 kJ/m³。通过与常规补气循环的比较，该混合工质及回热循环具有用于冬季采暖的潜力和可行性。此外，由于高沸点组分的加入，传统CO₂循环过高的运行压力也得到了很好的控制，这也更有利于该系统的实际应用。

关键词: 环保混合工质, 回热热泵, 制热性能, 理论研究

CLC Number:

TK 11⁺5

LUO Jielin, YANG Kaiyin, ZHAO Zhen, WANG Qin, CHEN Guangming. Heating performance of recuperative heat pump using low-GWP mixed refrigerant[J]. CIESC Journal, 2021, 72(S1): 84-90.

罗介霖, 杨凯寅, 赵朕, 王勤, 陈光明. 低GWP混合工质回热热泵采暖性能[J]. 化工学报, 2021, 72(S1): 84-90.

Figures/Tables 9

Fig.1 Schematic diagram of recuperative heat pump cycle with mixed refrigerant

Fig.2 Schematic diagram of vapor-injection heat pump cycle

Table 1 Optimized COP verification

热源进/出	热汇进/出	COP（文献）^[21]	COP（本文模型）	相对偏差
10℃/5℃	15℃/70℃	4.1835	4.2097	0.6264%
10℃/5℃	35℃/70℃	3.5851	3.4777	-2.9955%
15℃/5℃	15℃/70℃	4.2635	4.3442	1.8931%
25℃/5℃	25℃/70℃	4.2388	4.1855	-1.2574%
45℃/5℃	45℃/70℃	3.4979	3.6121	3.2660%

Fig.3 Variation of COP with ambient temperature

Fig.4 Variation of VHC with ambient temperature

Fig.5 Variation of optimized pL with ambient temperature

Fig.6 Variation of optimized pH with ambient temperature

Fig.7 Variation of optimized x(CO2) with ambient temperature

Fig.8 Variation of COP with x(CO2) at ambient temperature of -7℃

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