Characteristics of velocity and thickness distribution of liquid film in vertical falling tube

doi:10.11949/j.issn.0438-1157.20151953

Abstract

Abstract:

The flow characteristic of the falling liquid film in the scrubbing-cooling tube was researched in this paper. The ultrasound Doppler velocimetry was adopted to measure the velocity and thickness distribution of the liquid film non-instrusively at different circumferential and axial position. The Reynolds number ranged from 1.0×10⁴ to 3.1×10⁴. The results showed that both the velocity and thickness of the liquid film were the largest at the 0° position, leading to unevener thickness distribution and the separation of the local liquid film and the sharp increase of the liquid film thickness at the 8° and 16° positions. In the axial direction, because of the effect of gravity, the liquid film velocity increased with the increase of flow distance when the Reynolds numbers was less than 2.0×10⁴, whereas, it decreased at large Reynolds numbers since that the resistance became a dominant factor. Both of the thickness and velocity of global liquid film increased with increasing Reynolds number. Furthermore, the increase of the Reynolds numbers made the liquid film more unstable.

Key words: gas-liquid flow, turbulence, film, velocity measurement, thickness measurement, ultrasound Doppler velocimetry

摘要：

对洗涤冷却管内垂直降膜的流动特性进行研究,采用超声波多普勒测速仪对管内不同周向以及轴向位置的液膜厚度和速度进行了无接触式的测量,液膜Reynolds数范围为1.0×10⁴~3.1×10⁴。结果表明:在0°周向位置上液膜厚度与速度均达到最大值,导致该位置局部液膜厚度过大而不能保持稳定,部分液体脱离液膜表面,此外还造成了8°和16°位置的液膜厚度激增。在轴向上,当Reynolds数小于2.0×10⁴时,液膜速度在重力作用下随流动距离增加而增加,反之,液膜速度因为流动阻力会随距离增加而减小。随着Reynolds数的增大,液膜平均厚度和速度呈增大趋势。此外,Reynolds数的增大还会使得液膜更加不稳定。

关键词: 气液两相流, 湍动, 膜, 速度测量, 厚度测量, 超声多普勒测速仪

CLC Number:

TQ021

WANG Jing, WANG Yifei, YAN Liucheng, WU Ziwei, YU Guangsuo. Characteristics of velocity and thickness distribution of liquid film in vertical falling tube[J]. CIESC Journal, 2016, 67(6): 2239-2245.

王晶, 王亦飞, 颜留成, 伍子玮, 于广锁. 管内垂直下降液膜速度与厚度分布特性[J]. 化工学报, 2016, 67(6): 2239-2245.

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