外环状弹性壁布膜器及超薄降膜厚度

Elastic wall distributor of outer annular falling film and its ultra-thin characteristics

研发了竖直管外环状弹性壁降膜分布器,可以产生微米量级厚度均匀的超薄降膜流动。由弹性薄壁轴对称变形协调性决定,该布膜器具有均匀性和稳定性内在机理。理论分析导出了初始膜厚及布膜流量与布膜器内液柱高度的线性关系,并通过布膜器操作参数及降膜流量等实验数据进行了验证。实验结果表明,该布膜器对降膜管壁的润湿性能已经达到由固液界面性质决定的最小润湿流率。

A new type of elastic wall distributor of outer annular falling film was developed.This method could create a uniform annular channel for the micron-size ultra-thin falling film flow,which could be precisely controlled.This distributor had homogeneity and stability of internal mechanism due to the axisymmetrical deformation coordination characteristics of elastic wall and it could generate negative feedback responses to fluid pressure changes sensitively.According to the theory of thin shell and Amonton law of friction,the linear relationship between initial film thickness and liquid height was given.Also,the equation of falling film flow was established.Experiments were performed using water and 30% glycerol aqueous solutions at lower flow rates.The results indicated that the two equations obtained were in good agreement with experimental data and could be used as the design equations for engineering applications. The experiments also revealed that the vertical tube with a length of 0.6 m and a diameter of 14 mm could be completely wetted by the ultra-thin falling film 0.157 mm thick using the elastic wall distributor.And the wetting performance of the distributor reached the dimensionless minimum wetting rate,which was dependent on the properties of the solid-liquid interface.Compared with other liquid distributors,the elastic wall distributor gave the best performance of hydrodynamics.