竖直多孔平板上液膜流动特性的研究

doi:10.11949/0438-1157.20201737

摘要/Abstract

摘要：

孔结构被广泛应用于传质塔填料中，对填料上的液膜流动和传质行为影响较大。对竖直光板和多孔板上的液膜流动进行了三维模拟，并通过实验验证了模拟的准确性。通过模拟研究了孔结构对液膜流动特性的影响。结果表明，干燥孔会阻碍液膜的铺展，而润湿孔促进液膜的铺展。与光板相比，多孔板上的液膜具有起伏波，这将影响液膜的厚度分布和速度分布。液膜厚度波动和水平方向的速度波动随着孔径的增加而增加，而竖直流动方向的速度随着孔径的增加而降低。当孔径增加到一定值时，毛细波将出现在孔中的液膜中，这大大增加液膜水平方向上的波动速度，而降低流动方向上的速度。当孔径继续增加到临界值时，液膜将破裂。多孔板上孔内和气侧区域存在涡旋，能够促进内部液体交换和增大气侧扰动，从而增强传质能力。

关键词: 液膜, 孔板, 润湿性, 波动特性, 流型

Abstract:

The pore structure is widely used in mass transfer tower packing, which has a great influence on the liquid film flow and mass transfer behavior on the packing. However, no relevant research has been conducted on the wetted area and wave characteristics of the porous plates. In this work, three-dimensional simulations of the liquid film flow on the vertical smooth and porous plates were carried out and verified by experimental results. The effects of the holes on the liquid film flow behavior were studied. The results show that the flow patterns on the vertical porous plates and the smooth plate are almost the same, namely droplet, rivulet, and closed film flow. Dry holes will hinder the spreading of the liquid film, while the wet holes will promote it. Compared to the smooth plate, the liquid film on porous plates has sinuous waves, which will affect the distribution of film thickness and the wave velocity. The sinuosity of liquid film thickness and the horizontal velocity will increase with the increase of hole diameter, while the vertical flow velocity will decrease with the increase of hole diameter. When the hole diameter increases to certain value, capillary waves will appear on the liquid film in the hole, which will greatly enhance the horizontal wave velocity and reduce the vertical velocity in the hole. When the hole depth is 0.5 mm, a hole with a diameter of 4 mm will produce capillary waves. However, if the hole diameter continues to increase to a critical value, the liquid film will rupture. There are vortices on the in-hole and gas side of the porous plate, which can promote the internal liquid exchange and enhance the gas side disturbance, thus enhance mass transfer.

Key words: liquid film, hole plate, wettability, wave characteristic, flow pattern

中图分类号:

TQ 026.2

朱业铭, 刘金平, 许雄文, 朱丹丹. 竖直多孔平板上液膜流动特性的研究[J]. 化工学报, 2021, 72(8): 4081-4092.

Yeming ZHU, Jinping LIU, Xiongwen XU, Dandan ZHU. Research on liquid film flow characteristics of vertical porous plate[J]. CIESC Journal, 2021, 72(8): 4081-4092.

图/表 16

图1 计算域示意图

Fig.1 Schematic diagram of calculation domain

表1 模型边界条件

Table 1 Model boundary conditions

Zone name	Boundary conditions
inlet	velocity-inlet(UDF, Nusselt velocity distribution)
outlet	pressure-outlet (0 Pa)
top	symmetry
plate	no-slip wall with contact angle
side	no-slip wall with contact angle
hole	symmetry

图2 实验装置示意图1—pump;2—valve;3—liquid rotameter;4—collecting tank;5—fluid feed;6—test plate

Fig.2 Experimental setup

图3 水与铝板的平衡接触角

Fig.3 Equilibrium contact angle between water and aluminium plate

图4 红外热像仪成像示意图

Fig.4 Photo by infrared thermal imager

表2 光板和多孔板模型的网格尺寸

Table 2 Mesh size of nonporous and porous plates

光板			H=0.25 mm) 多孔板，(D=1 mm,S=1 mm,
网格数/万	最小网格体积/mm³	最大网格体积/mm³	网格数/万	最小网格体积/mm³	最大网格体积/mm³
5.2	0.1	0.35	43	0.0029	0.082
11.8	0.022	0.16	91	0.0013	0.058
22.5	0.016	0.12	143	0.0004	0.056
55.7	0.0065	0.065	200	0.0004	0.04

图5 网格独立性检查(D=1 mm，S=1 mm，H=0.25 mm)

Fig.5 Grid independence

图6 实验与模拟液膜覆盖率的对比(D=1 mm，S=1 mm，H=0.25 mm)

Fig.6 Comparison of wetted area between experiment and simulation

图7 光板与多孔板液膜覆盖率对比(D=1 mm，S=1 mm，H=0.25 mm)

Fig.7 Comparison of liquid film coverage between smooth plate and porous plate

图8 光板与多孔板的流型对比(D=1 mm，S=1 mm，H=0.25 mm)

Fig.8 Comparison of flow patterns between smooth plate and porous plate

图9 不同孔径下的相界面(VOF=0.5，Re=298, S=1 mm，H=0.25 mm)

Fig.9 Phase interfaces with different diameters

图10 不同孔径下的封闭液膜形态 (z = -15 mm，Re=298，S=1 mm，H=0.25 mm)

Fig.10 Closed film morphology with different diameters

图11 不同孔径下的封闭液膜厚度分布 (z = -15 mm，Re=298，S=1 mm，H=0.25 mm)

Fig.11 Closed film thickness distribution with different diameters

图12 不同孔径下的液膜流动形态实验（Re=298，S=1 mm，H=0.25 mm）

Fig.12 Experiments of liquid film flow pattern with different diameter

图13 封闭液膜速度分布(z = -15 mm，Re=298，S=1 mm，H=0.25 mm)

Fig.13 Velocity distribution of closed film

图14 封闭液膜流线(z = -15 mm，Re=298，S=1 mm，H=0.25 mm)

Fig.14 Streamline of closed film

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