Dynamics of nanoscale thin liquid films during coalescence and chemical reaction of droplets

•Flow field and interface near contact line of reacting droplets were studied.•A 3D method was developed to characterize film structure during reaction.•Film structure deforms and a convex interface appears at the central region.•Reaction rate obtained decreases exponentially with increasing film he...

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Bibliographic Details
Published in:Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2021-10, Vol.422, p.130071, Article 130071
Main Authors: Ma, Tengxiao, Zhao, Yabo, Zhou, Leping, Du, Xiaoze
Format: Article
Language:English
Subjects:
Chemical reaction
Droplet
Flow characteristics
Interface structure
Thin liquid film
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Summary:•Flow field and interface near contact line of reacting droplets were studied.•A 3D method was developed to characterize film structure during reaction.•Film structure deforms and a convex interface appears at the central region.•Reaction rate obtained decreases exponentially with increasing film height. The understanding of flow characteristics and interface structure evolution during the chemical reaction of droplets are important for many industrial processes. In this paper, qualitative observation and quantitative measurement are implemented at the region near the contact line of acetic acid and ammonium hydroxide droplets to study the flow field and interface evolution during the neutralization reaction of these testing fluids by an observation technique based on evanescent wave illumination. A three-dimensional sub-region method for characterizing the interface structure of the thin liquid film during droplet reaction is developed. The interface structures and velocity fields of the thin liquid films obtained by this method reveal that at the moment of reaction the mesoscopic interface structure deforms severely and the convex interfaces appear at the central regions due to the impact of the initial kinetic energy and the chemical reaction of droplets. Meanwhile, the reaction rate is found to decrease exponentially with the increase of height in the thin liquid film. The work provides valuable information for further understanding the mechanisms of formation and transport of the mesoscale interface structure during chemical reactions.
ISSN:1385-8947
1873-3212
DOI:10.1016/j.cej.2021.130071