气液传质液滴界面的Marangoni对流

通过氮气吹扫双组分液滴,用激光投影法定性观察由于轻组分向气相扩散导致的Marangoni对流结构,结果表明Marangoni对流以小尺度涡流结构和大尺度对称循环流动的形式出现,其中乙醇-水体系首先出现小尺度涡流结构,涡流不断长大合并;丙酮-水体系则以大尺度对称循环对流结构为主,随后在近界面处形成小尺度涡流结构。采用氮气吹扫乙醇-水及丙酮-水静止悬垂单液滴的方法,通过比较实验测量传质系数与理论预测值,表明液滴近界面处Marangoni对流小尺度涡结构对传质促进作用较小,而液滴内大尺度循环对流结构对传质促进作用大。

Marangoni convection at droplet interface during gas-liquid mass transfer

By sweeping binary droplets with N₂ gas,the Marangoni convection driven by desorption of light component into gas phase is observed with the help of laser shadowgraph optical method.The results show that Marangoni convection arises as small-scale vortex and large-scale symmetrical circular flow.The small-scale vortex structure appears in the ethanol-water droplet at the very beginning,and then vortex structure develops and merges to form larger vortex flow.At the interface of acetone-water binary droplet,symmetrical circular flow appears at first,and then vortex flow arises in the circular flow.For the quiescent single binary droplet composed of ethanol-water and acetone-water separately,the mass transfer coefficient is measured to compare with theoretical prediction while N₂ gas purges the gas-liquid interface. Experimental results show that the large-scale symmetrical circular inside the droplet can promote mass transfer process much better than the small-scale vortex near the interface of droplet.