倾斜上升管内气液两相弹状流壁面传质特性研究

采用VOF模型对倾角为45°、80°、85°三种情况下倾斜上升管内弹状流的壁面传质特性进行了研究.传质特性通过其与壁面切应力的类比关系来体现.数值模拟结果表明,低混合物流速时,上管壁面切应力在液膜区有明显波动,而下管壁面切应力分布则比较光滑.随着混合流速的增大,液膜区上下壁面切应力分布趋于一致.管子下壁面切应力平均值大于管子上壁面,在Taylor气泡运动速度较低时较为突出.随着Taylor气泡速度的增大,管子上下壁面的切应力平均值趋于相同.相同的混合流速下倾斜角度越大,上下管壁的切应力分布越趋于近似.下降液膜区的壁面切应力平均值大于Taylor气泡尾迹区域.根据Chilton-Colburn的类比关系,壁面切应力的规律完全适用于壁面传质系数.

A STUDY ON WALL MASS TRANSFER CHARACTERISTICS IN A GAS-LIQUID INCLINED UPWARD SLUG FLOW

With VOF model,the characteristics of wall mass transfer coefficient in a gas-liquid inclined upward slug flow are studied.The wall mass transfer coefficient is characterized by wall shear stress.The simulated results show that the wall shear stress in the falling film zone on the top wall has a significant fluctuation at lower mixture superficial velocities.Nevertheless,the wall shear stress distribution in the same zone on the bottom wall appears smoothly.With increased mixture superficial velocities,the difference between top and bottom wall shear stresses become less obvious.The bottom wall shear stress is usually greater than that of the top wall and the difference is obvious when the Taylor bubble rising velocity is small.However,with increased Taylor bubble rising velocities,the difierence is less obvious.The difference vanishes with increased inclined angles at the same mixture velocities.The wall shear stress in the falling film zone is usually greater than that in the Taylor bubble wake zone.According to the analogy of Chilton-Colburn.wall shear stress can be used to characterize the wall mass transfer coefficient.