Effects of liquid viscosity on flows inside and outside a bubble diffuser pipe
Effects of liquid viscosity on flows inside and outside a bubble diffuser pipe
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液体粘度对气泡扩散管内外流动的影响
DOI：
10.1016/j.expthermflusci.2015.03.025
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发表时间：
2015
影响因子：
3.2
通讯作者：
Akio Tomiyama
中科院分区：
文献类型：
--
作者：
Ryo Sato;Kosuke Hayashi;Akio Tomiyama
研究了液体粘度对气泡扩散器内外流动的影响。甘油-水溶液和空气分别用于液体和气相。在一个矩形水箱中放置了一个顶部有5个曝气孔，底部有较大开口的圆形管道。管径20 mm，孔径5 mm。S的液体粘度μ为1~100兆帕斯卡，总气体流量为3×10−4~7×10−4m3/S。用高速摄像机观察管道内外的流动，通过捕捉每个孔产生的气泡来测量每个曝气孔的气体流量。液体通过曝气孔和通气口进入管内，形成间歇性弹状流的波状流态。得到的结论如下：(1)QIN和μ_L的增加减少了段塞扰气的发生频率，使得在QIN和μ较高时各孔的气体流量趋于均匀；(2)在高μ时，液滴从曝气孔落入管内引起的变形是低μ陆界面上的界面波引起的主要触发因素；(3)三岛和石井(1980年)提出的无粘性流体的段塞判据不仅适用于低μ液体，而且还适用于高μ液体，因为即使在本实验所测试的高粘度条件下，波的增长率也远大于粘滞阻尼率。(4)Davidson-Schüler(Davidson and Schüler，1960)给出了气泡直径的合理估计，不仅适用于低粘度液体，也适用于高粘度液体，前提是段塞流的影响很小。
Effects of liquid viscosity on flows inside and outside a bubble diffuser pipe were investigated in this study. Glycerol–water solutions and air were used for the liquid and gas phases, respectively. A circular pipe having five aeration holes on the topside and larger opening on the bottom side was placed in a rectangular water tank. The pipe diameter was 20 mm and the hole diameter was 5 mm. The liquid viscosityμLranged from 1 to 100 mPa s and the total gas flow rateQINranged from 3 × 10−4to 7 × 10−4m3/s. The flows inside and outside the pipe were observed using a high-speed video camera and the gas flow rates from each aeration hole were measured by capturing bubbles generated from each hole. The liquid entered into the pipe through the aeration hole and the opening, resulting in wavy flow pattern with intermittent slugging. The conclusions obtained are as follows: (1) the increases inQINandμLdecrease the frequency of slugging disturbing aeration, so that the gas flow rate from each hole becomes uniform at highQINandμL, (2) the main triggers of slugging are interfacial waves at lowμLand interface deformation caused by liquid drops falling from the aeration holes into the pipe at highμL, (3) a slugging criterion for inviscid fluids proposed by Mishima and Ishii (1980) is applicable not only to lowμLliquids but also to highμLliquids because the wave growth rate is much larger than the viscous damping rate even at high viscosities tested in the present experiments, and (4) the Davidson–Schüler correlation (Davidson and Schüler, 1960) gives reasonable estimations of the bubble diameter not only for low viscosity liquids but also for high viscosity liquids, provided that the influence of slugging is small.