流体在光滑圆条上的降膜流动分析

doi:10.16085/j.issn.1000-6613.2024-0705

摘要/Abstract

摘要：

降膜脱挥具有相接触面积大、脱挥效率高、经济性好的优点，常作为从聚合物中脱除挥发性物质的重要手段，其脱挥效果与流体在落条上的降膜状态息息相关。本文选用糖浆溶液模拟聚合物系，通过漏斗降膜元件分析流体沿光滑圆条的自由降膜过程，考察了流体黏度、流量和环缝宽度对降膜的影响。结果表明：当漏斗持液器环缝处的液位压力大于表面张力时，流体通过环缝在圆条上形成降膜，且流体黏度越大，润湿性越弱，稳定成膜对应的环缝宽度越大；环缝宽度为1.5mm和2.5mm时，不同黏度的流体均能稳定成膜，为优选的环缝宽度；在确定的流体黏度或环缝宽度下，稳定降膜高度与降膜流量呈递增关系。环缝宽度越大，流体黏度越小，稳定降膜对应的流量越大；随着糖浆黏度和降膜流量增加，膜厚度逐渐增加，在考察的糖浆黏度和降膜流量范围内，膜厚度在0.94~3.48mm之间，为降膜脱挥提供了基础数据支持。

关键词: 聚合物脱挥, 降膜流动, 稳定成膜高度, 膜厚

Abstract:

Falling film de-volatilization has the advantages of large phase contact area, high de-volatilization efficiency and good economy, and is often used as an important means to remove volatile substances from polymers, and its de-volatilization effect is closely related to the state of the descending film of the fluid on the falling bar. In this paper, a molasses solution was selected to simulate the polymer system, and the free film descent process of the fluid along the smooth circular bar was analyzed by the funnel film descent element, and the effects of fluid viscosity, flow rate, and annular slit width on the film descent were investigated. The results showed that when the liquid level pressure at the ring slit of the funnel holder was greater than the surface tension, the fluid formed a descending film on the circular strip through the ring slit, and the larger the fluid viscosity was, the weaker the wettability was, and the larger the ring slit width corresponded to the stabilized film. When the ring slit widths were 1.5mm and 2.5mm, the fluids with different viscosities could be stabilized to form a film, which was the preferred ring slit width. At a definite fluid viscosity or ring slit width, the stabilized descending film under the determined fluid viscosity or ring seam width, the stable falling film height had an increasing relationship with the falling film flow rate. The larger the ring seam width, the smaller the fluid viscosity, and the larger the flow rate corresponding to the stabilized descending film. With the increase of syrup viscosity and descending film flow rate, the film thickness gradually increased, and the film thickness ranged from 0.94mm to 3.48mm within the investigated range of syrup viscosity and descending film flow rate, which provided the basic data support for the descending film de-volatilization.

Key words: polymer de-volatilization, falling film flow, stabilized film height, film thickness

中图分类号:

TQ021.1

邹志鹏, 潘全旺, 赵陈, 沈海涛, 丛梅, 赵基钢. 流体在光滑圆条上的降膜流动分析[J]. 化工进展, 2025, 44(6): 3405-3412.

ZOU Zhipeng, PAN Quanwang, ZHAO Chen, SHEN Haitao, CONG Mei, ZHAO Jigang. Analysis of falling film flow of fluid over a smooth circular bar[J]. Chemical Industry and Engineering Progress, 2025, 44(6): 3405-3412.

图/表 18

表1 不同比例的糖浆水溶液黏度

糖浆质量分数/%	溶液黏度/mPa·s
70	33
80	110
90	426
95	1239
100	2239

图1 光滑圆条降膜设备1—液体分布器；2—变频器；3—齿轮泵；4—光滑圆条；5—导流漏斗；6—漏斗元件；7—收集器；8—电子天平

表2 结构参数

高度/mm	外径/mm	内径/mm	光滑圆条外径/mm	狭缝宽度/mm
50	80	3	2	0.5
50	80	5	2	1.5
50	80	7	2	2.5
50	80	9	2	3.5
50	80	11	2	4.5

图2 不同黏度糖浆溶液接触角

图3 不同黏度糖浆溶液接触角和时间关系

图4 光滑圆条降膜不稳定流动现象

图5 光滑圆条降膜稳定流动现象

表3 稳定成膜时不同环缝宽度与黏度之间对应关系

环缝宽度/mm	黏度/mPa·s
环缝宽度/mm	33	110	426	1239	2239
0.5	稳定	稳定	不稳定	不稳定	不稳定
1.5	稳定	稳定	稳定	稳定	稳定
2.5	稳定	稳定	稳定	稳定	稳定
3.5	波动	波动	稳定	稳定	稳定
4.5	不稳定	不稳定	不稳定	不稳定	波动

图6 稳定降膜高度示意图

图7 不同环缝宽度条件下降膜流量与降膜高度的关系

图8 不同黏度条件下降膜流量与降膜高度关系

图9 光滑圆条降膜流动三维模型

图10 网格划分结果

图11 网格无关性检验

表4 实验膜厚与计算膜厚的对比结果

降膜流量/g·s^-1	实验膜厚/mm	计算膜厚/mm	相对误差/%
0.12	1.00	1.09	8.57
0.16	1.05	1.21	16.12
0.28	1.16	1.41	21.22
0.31	1.20	1.45	20.88
0.35	1.21	1.50	24.24

图12 糖浆溶液在圆条上的成膜状态

图13 糖浆黏度对膜厚度的影响

图14 降膜流量对膜厚度的影响

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