一种新型可调涡流管膨胀的跨临界CO2热泵系统性能研究
Performance research on a novel adjustable transcritical CO2 heat pump system with vortex tube expansion
摘要：
在跨临界CO2热泵循环中,采用涡流管膨胀替代常规节流阀的Maurer模型可减小节流损失、提高系统性能,但存在不能自动调节的难题。通过对Maurer模型进行改进,本文提出一种新型可调涡流管膨胀的跨临界CO2热泵系统,通过建立理论模型模拟分析了新型系统的性能特点,并与膨胀阀节流的常规系统和Maurer模型的性能进行了对比分析。研究结果表明:1) 新型系统能实现对系统制热量与压缩机排气温度的自动控制。当蒸发温度改变时,新型系统可以通过改变电子流量调节阀开度实现对调节压缩机排气温度的控制,还可以通过改变调节压缩机频率实现对冷质量分数与涡流管热端出口温度的控制,进而调节系统制热量。新型系统保证了涡流管热端出口温度和压缩机排气温度不超过120 ℃警戒值的同时维持了较高的制热量,改善了系统性能。2) 新型系统的性能优于常规系统和Maurer模型。通过将涡流管热端出口温度与调节压缩机排气温度控制在较高水平,新型系统能具有更高的制热量和更好的性能。当全年蒸发温度在-10～10 ℃间变化时,新型系统的COP和制热量较常规系统分别增大了13.1%和16.7%,较Maurer模型分别增大了2.7%和6.1%。新型系统对系统性能的改善效果会随着蒸发温度变化范围的扩大更加显著。
Abstract：
In the transcritical CO2heat pump cycle, the Maurer model using vortex tube expansion instead of conventional throttle valves can reduce the throttling loss and improve the system performance, but the Maurer model has a deficiency in adjustability. By improving the Maurer model, this paper proposes a novel adjustable transcritical CO2heat pump system with vortex tube expansion. A theoretical model is established to simulate and analyse the performance characteristics of the novel system, and the performance is compared with that of the conventional system with expansion valve throttling and the Maurer model. The research shows the results as follows: 1) The novel system can automatically control the heating capacity of the system and the discharge temperature of the compressor. When the evaporation temperature changes, the novel system can control the discharge temperature of the adjusting compressor by varying the opening of the electronic flowrate control valve, and can also control the cold mass fraction and the hot exit temperature of the vortex tube by changing the frequency of the adjusting compressor, thereby adjusting the heating capacity of the system. The novel system brings a high heating capacity and improves performance while ensuring that the hot exit temperature of the vortex tube and the discharge temperature of the compressor do not exceed the warning value of 120 ℃. 2) The performance of the novel system is better than that of the conventional system and the Maurer model. The novel system can obtain a higher heating capacity and better performance by maintaining the hot exit temperature of the vortex tube and the discharge temperature of the adjusting compressor at a high level. When the evaporation temperature varies from -10 ℃ to 10 ℃ throughout the year, the COP and heating capacity of the novel system increase by 13.1% and 16.7% respectively compared with those of the conventional system, and increase by 2.7% and 6.1% respectively compared with those of the Maurer model. The improvement effect of the novel system on system performance will be more significant as the range of evaporation temperature variation expands.
Keywords:CO2; heat pump; vortex tube; Maurer model; cold mass fraction; evaporation temperature; coefficient of performance (COP)