Abstract:

The pressure drops characteristics of supercritical CO₂ fluid in a heating mini-channel with an inner diameter of 0.75mm under varying flow direction conditions were investigated experimentally. The results showed that the Different flow directions (horizontal flow, vertical upward flow, and vertical downward flow), the total pressure drop, frictional pressure drop, and accelerational pressure drop consistently decreased with the increase in system pressure, but increased with the rise of mass flow rate, heating power, and inlet temperature, irrespective of the flow directions. Conversely, the gravitational pressure drop increased with the increase of system pressure and mass flow rate, but decreased with the increase of heating power and inlet temperature in vertical flow directions. When the system parameters were held constant, the frictional pressure drop was the most significant proportion to the total pressure drop, while the gravitational pressure drop contributed the least. A comparison of the pressure drop data across two different inner diameters revealed that the total pressure drop of the supercritical CO₂ fluid was consistently higher in smaller diameters, highlighting the significant impact of tube diameter on total pressure drop changes.

Key words: supercritical CO₂, different flow direction, total pressure drop, frictional pressure drop, accelerational pressure drop, gravitational pressure drop

摘要：

针对不同流动方向上超临界CO₂流体在小流道加热管径为0.75mm内的压降特性进行了实验研究。结果表明，不同流动（水平流动、垂直向上流动以及垂直向下流动）方向上，实验总压降、摩擦压降以及加速度压降均随着系统压力的升高而逐渐减小，而随着质量流量的增大、加热功率以及进口温度的升高而增大。然而，在垂直流动方向上重力压降随着系统压力的升高以及质量流量的增大而逐渐增大，但随着加热功率以及进口温度的升高而逐渐减小。当系统压力、质量流量、加热功率以及进口温度保持恒定时，不同流动方向上超临界CO₂流体的摩擦压降均在实验总压降中所占有的比例最大，而重力压降在实验总压降中所占有的比例最小。通过两种测试管径的压降数据比较可知，超临界CO₂流体在不同流动方向上实验总压降的变化趋势始终保持一致，并且小管径的实验总压降远大于大管径的实验总压降，从而说明测试管径的尺寸大小对实验总压降的变化有着显著影响。

关键词: 超临界CO₂, 不同流动方向, 总压降, 摩擦压降, 加速度压降, 重力压降