超临界CO2热泵蛇形管气冷器传热特性研究

为了减少能源消耗、提高CO₂热泵的效率，基于Fluent软件，采用数值模拟方法对超临界CO₂在蛇形管气冷器中的传热特性进行研究。主要探究蛇形管内超临界CO₂的流动特性，通过改变操作压力、CO₂和冷却水的质量流量，分析蛇形管的传热性能。结果表明,蛇形管中离心力周期反向，会使温度和速度梯度呈周期性的内侧和外侧交互扩散的趋势；超临界CO₂压力越靠近临界点，平均传热系数越高，压力为8 MPa下的平均传热系数相较于9 MPa和10 MPa分别提高了24.37%和42.53%；超临界CO₂的平均传热系数随着CO₂质量流量的增加而增大，随着冷却水质量流量的增加而降低，冷却水质量流量的增加不会对峰值点的传热系数产生影响，但会使峰值点出现的位置提前。研究结果为超临界CO₂热泵蛇形管气冷器的设计、运行及热效率的提升提供了理论依据。

Research on heat transfer characteristics of serpentine tube

In order to reduce energy consumption and improve the efficiency of CO2 heat pumps, a numerical simulation method was used to study the heat transfer characteristics of supercritical CO2 in serpentine tube air cooler based on Fluent software. The flow characteristics of supercritical CO2 in a serpentine tube were mainly investigated. The heat transfer performance of the serpentine tube was analyzed by changing the operating pressure, the mass flow rate of CO2, and cooling water. The results show that the periodic reversal of centrifugal force in a serpentine tube will cause the temperature and velocity gradients to exhibit a periodic trend of internal and external interdiffusion; The closer the supercritical CO2 pressure is to the critical point, the higher the average heat transfer coefficient is. The average heat transfer coefficient at a pressure of 8 MPa is 2437% and 4253% higher than that at 9 MPa and 10 MPa, respectively. The average heat transfer coefficient of supercritical CO2 will increase with the increase of the CO2 mass flow rate, and decrease with the increase of the cooling water mass flow rate. The increase of the cooling water mass flow rate will not have an impact on the heat transfer coefficient of the peak point, but will advance the location of the peak point. The research results provide a theoretical basis for the design, operation and thermal efficiency improvement of the serpentine tube air cooler of supercritical CO2 heat pump, and have important guiding significance for the application of high efficiency heat exchangers.