Ultrasound-assisted gas–liquid mass transfer process in microreactors: The influence of surfactant, channel size and ultrasound frequency
Ultrasound-assisted gas–liquid mass transfer process in microreactors: The influence of surfactant, channel size and ultrasound frequency
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微反应器中超声辅助气液传质过程：表面活性剂、通道尺寸和超声频率的影响
DOI：
10.1016/j.cej.2020.126720
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发表时间：
2021
影响因子：
15.1
通讯作者：
Chen Guangwen
中科院分区：
文献类型：
--
作者：
Zhang Qiang;Dong Zhengya;Zhao Shuainan;Liu Zhikai;Chen Guangwen
在超声微反应器中，研究了不同频率（20、28、40 kHz）和通道尺寸（0.5 × 0.5、1.0 × 1.0、1.5 × 1.5、2.0 × 2.0 mm 2）的超声对气液Taylor流流体力学和传质行为的影响。超声辐照段塞泡时，在其周围产生空化微流涡的同时，在段塞泡上激发出强烈的气泡振荡，气泡振荡的幅度随着通道尺寸的减小而减小，这是由于超声对段塞泡的约束作用。沟道尺寸为1.0 × 1.0mm2是消除限制效应的临界尺寸。在较低的超声频率下，气泡振荡和空化微流现象更为强烈，传质增强效果也更为显著。在频率为20 kHz，功率密度为0.14 W/mL时，总体积传质系数提高了22倍。表面活性剂（SDS）的加入使界面张力降低，使气泡振荡幅度增大。振荡振幅的增加使比表面积增大，从而导致总体积传质系数随表面活性剂浓度的增加而增加。通过建立传质模型，对超声波强化气液传质的具体效果进行了定量分析，该模型能较好地预测液侧传质系数和比表面积。
Ultrasound effect on the hydrodynamics and mass transfer behavior of gas–liquid Taylor flow is studied in ultrasonic microreactors with different frequencies (20, 28, 40 kHz) and channel dimensions (0.5 × 0.5, 1.0 × 1.0, 1.5 × 1.5, 2.0 × 2.0 mm2). Upon ultrasound irradiation, intense bubble oscillation is excited on the slug bubble, accompanied by cavitation microstreaming vortices around it. The amplitude of bubble oscillation decreases with the decrease of channel dimension as a result of the confinement effect. Channel dimension of 1.0 × 1.0 mm2is considered as the critical dimension above which the confinement effect would be eliminated. More intensive bubble oscillation and cavitation microstreaming are observed at lower ultrasound frequency, where more significant mass transfer enhancement is also observed. At frequency of 20 kHz, the overall volumetric mass transfer coefficient is improved by 22 times at the power density of 0.14 W/mL. Adding surfactant (SDS) in the liquid increases the amplitude of bubble oscillation due to the decrease of interfacial tension. Such an increase in the oscillation amplitude enlarges the specific surface area, leading to an increase in the overall volumetric mass transfer coefficient with the increase of surfactant concentration. The detailed effect that how gas–liquid mass transfer would be enhanced by ultrasound is quantified by a mass transfer model, which could predict both the liquid side mass transfer coefficient and the specific surface area satisfactorily.