气液传质液滴界面的Marangoni对流

Marangoni convection at droplet interface during gas-liquid mass transfer

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。

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.