环境温度和热用户实际用热情况会影响供热回水温度,进而显著影响CO₂跨临界热泵系统性能。针对这一变工况问题,建立了CO₂跨临界热泵系统理论分析模型,采用理论分析方法考察了常规CO₂跨临界热泵系统和带回热器的CO₂跨临界热泵系统在不同供热回水温度下供热温度、制热性能系数COP_h等性能参数的变化规律。结果表明：对于两种CO₂跨临界热泵系统,随着供热回水温度的升高,系统供热温度在某一特定温度范围内迅速跃升,而后保持不变(常规热泵系统)或持续升高(带回热器热泵系统)；系统COP_h总体呈现下降趋势,且在较低的压缩机排气压力下,COP_h有较大的降低幅度。常规热泵系统中,最大供热回水温度随压缩机排气压力的升高呈线性上升趋势。与常规热泵系统相比,带回热器的热泵系统在一定程度上提升了系统供热温度和COP_h,压缩机排气压力越低,提升幅度越明显,在所考察的工况中,COP_h提升幅度最大可达97.3%。同时,带回热器的热泵系统在一定程度上避免了高供热回水温度下蒸发器侧无蒸发现象的发生,具备更好的高温工况适应性。

The ambient temperature and the actual heat demand of the user affect the heating return water temperature, which in turn significantly impacts the performance of CO2 transcritical heat pump systems. Aiming at this problem of variable working condition, a theoretical analysis model of the CO2 transcritical heat pump system was established. The variations in heating temperature, heating coefficient of performance (COPh), and other performance parameters of the conventional CO2 transcritical heat pump system and the CO2 transcritical heat pump system with heat regenerator were investigated by theoretical analysis method under different heating return water temperatures. The results show that for the two CO2 transcritical heat pump systems, with the increase of the heating return water temperature, the heating temperature of the system jumps rapidly in a specific temperature range, and then remains unchanged (conventional heat pump system) or continues to increase (with heat regenerator heat pump system). The COPh of the system generally shows a declining trend, with a larger decrease occurring at lower compressor discharge pressures. In conventional heat pump system, the maximum heating return water temperature increases linearly with the increase of compressor discharge pressure. Compared with the conventional heat pump system, the heat pump system with the heat regenerator increases the heating temperature and COPh of the system to a certain extent, with a larger increase occurring at lower compressor discharge pressures. In the working conditions under investigated, the increase range of COPh can reach a maximum of 97.3%. At the same time, the heat pump system with heat regenerator avoids the occurrence of no evaporation on the evaporator side under high heating return water temperature to a certain extent, and has better adaptability to high temperature conditions.

北京市教育委员会科学研究计划资助项目