A gas–liquid counter current flow may possibly occur in the U-tubes of the steam generator in a PWR due to loss of the residual heat removal during mid-loop operation. For safety analysis based on the one-dimensional multi-fluid simulation, correlations of the interfacial and wall friction factors are required. Experiments on air-glycerol water solution counter-current annular flows in a circular vertical pipe of 20 mm in diameter and 400 mm in length with a sharp-edged lower end, hence, were carried out to investigate the effect of the liquid viscosity on the flow structure and the interfacial and wall friction factors. The liquid flow rate, the pressure gradient and the liquid volume fraction were measured to evaluate the friction factors. The time-strip flow visualization technique was applied to flow images in the pipe for detailed observation. The obtained conclusions are as follows: (1) the flows under CCFL condition in the present study can be classified into two regimes, i.e. the rough film with disturbance waves forming at the lower pipe end (RF-I) and the disturbance waves flowing upward with dissipation and regeneration (RF-II), (2) the interfacial friction factor is independent of the liquid viscosity and mainly determined by the balance between the inertial and buoyant forces. The gas Froude number, J_G*, is the primal dimensionless group in correlating the interfacial friction factor, (3) the wall friction factor can be correlated in terms of the liquid Froude number J_L*, the liquid Reynolds number Re_L and the dimensionless pipe diameter D*, and (4) the correlations of the friction factors were proposed. The applicable ranges of the correlations are 0.58 ≤ J_G^*1/2 ≤ 0.78, 0.01 ≤ J_L^*1/2 ≤ 0.10, 0.15 ≤ Re_L ≤ 178 and 7.28 ≤ D* ≤ 17.79.

由于在中间回路运行过程中残留的热量流失，在PWR中蒸汽发生器的U型管中可能会发生气液逆流。对于基于一维多流体模拟的安全性分析，需要界面和壁摩擦系数的相关性。在直径为20 mm，长度为400 mm，下端尖锐的圆形垂直管中进行空气甘油水溶液的逆流环形流动实验，从而研究了液体粘度对其流动性的影响。流动结构以及界面和壁的摩擦因素。测量液体流速，压力梯度和液体体积分数，以评估摩擦系数。时带流动可视化技术应用于管道中的流动图像，以进行详细观察。得到的结论如下：（1）本研究中CCFL条件下的流动可分为两种形式，即在管下端形成扰动波的粗糙膜（RF-I）和向上流动的扰动波。对于耗散和再生（RF-II），（2）界面摩擦系数与液体粘度无关，并且主要由惯性力和浮力之间的平衡决定。气体弗洛德数，（2）界面摩擦系数与液体粘度无关，主要取决于惯性力和浮力之间的平衡。气体弗洛德数，（2）界面摩擦系数与液体粘度无关，主要取决于惯性力和浮力之间的平衡。气体弗洛德数，J _G *是与界面摩擦系数相关的原始无量纲基团，（3）壁摩擦系数可以根据液体弗洛德数J _L *，液体雷诺数Re _L和无量纲管径D *进行关联（4）提出了摩擦系数的相关性。的相关性的适用范围是0.58≤  Ĵ _ģ ^{* 1 /}  ≤0.78，0.01≤  Ĵ_大号^{* 1 /}  ≤0.10，0.15≤ 重新_大号 ≤178和7.28≤  d *≤17.79。