微通道内催化表面气泡生长及脱离的可视化实验

采用聚二甲基硅氧烷材料(PDMS)制备矩形截面的微通道,并在微通道壁面上沉积MnO₂作为催化剂,采用高速摄影仪对通流过程中过氧化氢催化分解生成氧气气泡的过程进行了可视化实验研究,分析了反应物的浓度和流量对气泡生长速度及脱离直径的影响.结果表明:气泡在微通道内催化表面的生长及脱离过程呈周期性变化的趋势;气泡生长可以分为快速生长和缓慢生长两个阶段,当t<3 s时气泡处于快速生长阶段,催化反应主要受动力学控制,当t≥3 s时扩散控制占主要地位,气泡生长速度随反应物浓度的升高而增大;气泡脱离直径受反应物浓度影响较小,受反应物流量影响较大,而且随液相反应物Reynolds数的增大线性降低.

Visualization experiments of bubble growth and detachment on catalytic surface in a microchannel

A rectangular microchannel was fabricated with polydimethylsiloxane (PDMS) material and MnO₂ catalysts were deposited on the wall of the microchannel. The growth and detachment process of oxygen bubbles generated by the catalytic reaction of H₂O₂ solution were recorded by a high speed camera. The effects of reactant concentration and flow rate on bubble growth rate and detachment diameter were also analyzed. The growth and detachment process of bubbles generated on the catalytic surface in the microchannel occurred periodically. Moreover, the bubble growth consisted of two processes, the initial fast growth process and the later slow growth process. Before 3 s, the generated bubbles were in a fast growth period, and reaction kinetics dominated the process. However, after 3s, reaction rate was controlled by diffusion, resulting in the fact that bubble growth rate increased with increasing reactant concentration. In addition, bubble detachment diameter was slightly affected by reactant concentration, while it was significantly affected by reactant flow rate and dropped linearly as Reynolds number increased.