Abstract: In order to improve the performance of CO2 transcritical heat pump heating system, a two-stage compression, two gas cooler and vapor injection regenerative system is proposed. Through the establishment of the thermodynamic model, the impact of various factors on the energy efficiency of the system is analyzed combined with the other three CO2 heat pump systems and R134a single-stage compression regenerative system. In addition, by constructing an economic evaluation model that comprehensively considers the initial investment cost and annual operating cost, combined with typical annual meteorological parameters, the total investment situation of each system in different cities during the operating cycle is studied. The results show that the two-stage compression, two gas cooler and vapor injection regenerative system is the optimal system scheme, which has the highest COPh and exceed R134a single-stage compression regenerative system. When the ambient temperature is 0℃ and the temperature of outlet/return water is 65/40 ℃, the theoretical COPh can reach 2.58, which is 9.1% higher than that of R134a system, and 22.5% higher than that of CO2 single-stage compression system, and the compressor discharge temperature doesn’t exceed the existing temperature limit. In the selected sample cities, the total investment cost of all heat pump systems during the operating cycle is the lowest in Shanghai and the highest in Shenyang, which shows that it is greatly affected by the climate region. Due to the high cost of the CO2 compressor, the total investment cost of CO2 heat pump system is higher than that of R134a system. With the improvement of CO2 heat pump technology and the expansion of production scale, when the cost of the compressor is reduced by 80%, the total investment cost of two-stage compression, two gas cooler and vapor injection regenerative system will be lower than that of R134a system.

Key words: CO2 heat pump, transcritical, heating, energy efficiency, economy

摘要： 为提高CO2跨临界热泵采暖系统的性能，提出了双级压缩双气冷器中间补气回热系统。结合其它三种CO2热泵系统和R134a单级压缩回热系统，通过建立热力学模型，分析各因素对系统能效的影响。此外，通过构建综合考虑初始投资成本和年运行成本的经济性评价模型，结合典型年气象参数，研究不同城市中各系统在运行周期内的总投资情况。结果表明，CO2热泵系统中，双级压缩双气冷器中间补气回热系统最优COPh最高且可以超过R134a单级压缩回热系统，在环境温度为0℃，出水/回水温度为65/40℃时，理论COPh可达2.58，比R134a系统高9.1%，比CO2单级压缩系统高22.5%，且排气温度不超过现有压缩机排气温度极限，是能效最优系统。在选定样本城市中，热泵系统运行周期内的总投资成本在上海最低，而在沈阳最高，可见总投资成本受气候区域影响较大。由于CO2压缩机成本过高，CO2热泵系统的总投资成本高于R134a系统。随着CO2热泵技术的提高和生产规模的扩大，当压缩机成本降低80%，CO2双级压缩双气冷器中间补气回热系统的总投资成本将低于R134a系统。

关键词: CO2热泵, 跨临界, 采暖, 能效, 经济