The liquid film thickness and hydrodynamic entrance length in a vertical tube was studied experimentally and numerically. Measurements using distilled water, 30 wt % MEA and 40 wt % sugar solutions were carried out to investigate the effects of liquid flow rate on the formation of the liquid film. The experimental results validate the new Navier‐Stokes based equation in cylindrical coordinates (Eq. 16) and the volume of fluid (VOF) model giving a competitively high prediction of the liquid film thickness especially in the low Reynolds number region. In addition, a new empirical model and an improved minimal surface model have been first proposed for calculation of the hydrodynamic entrance length, with a relatively reasonable average absolute relative deviation (AARD) of 3.03% and 6.83%, respectively. Furthermore, the effects of the hydrodynamic entry length on the gas–liquid interfacial area calculated by the improved minimal surface model were comprehensively studied, and can be ignored if the ratio of the liquid film length (y) and the hydrodynamic entrance length (λ_E) is lower than 10. However, it should be noted that the hydrodynamic entrance length cannot be ignored in packed columns in which the liquid flow is very complex due to the packings with different structures and materials. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2078–2088, 2018

中文翻译：

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沿垂直管的层流液流中的膜厚和流体动力入口长度的研究

对立管中的液膜厚度和流体动力入口长度进行了实验和数值研究。使用蒸馏水，30 wt％MEA和40 wt％糖溶液进行测量，以研究液体流速对液膜形成的影响。实验结果验证了新的基于Navier-Stokes的圆柱坐标系方程（等式16）和流体体积（VOF）模型，从而提供了具有竞争性的高液膜厚度预测，尤其是在低雷诺数区域。此外，首先提出了一种新的经验模型和一种改进的最小表面模型来计算水力入口长度，相对合理的平均绝对相对偏差（AARD）分别为3.03％和6.83％。此外，_E）小于10。但是，应该注意的是，由于填料的结构和材料不同，在液体流动非常复杂的填料塔中，流体动力学入口长度不能忽略。©2018美国化学工程师学会AIChE J，64：2078-2088，2018