Abstract
Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application.
Highlights
Published: 22 March 2021The impact of a liquid drop on a solid surface is ubiquitous and observed in many natural and industrial processes
The wettability pattern consist of 20 superhydrophilic wedges on a superhydrophobic background
The part of spray drops impacting on the superhydrophilic wedge quickly converted into a liquid film, whereas the droplets falling on the superhydrophobic region spontaneously moved towards either the superhydrophilic wedge or jumped-off from the surface
Summary
Published: 22 March 2021The impact of a liquid drop on a solid surface is ubiquitous and observed in many natural and industrial processes. Several parameters influence the drop impact dynamics; the surface wettability has an especially important role. Spray cooling is one of the important practical applications of drop impact on a surface and it has received significant attention in the present decade due to the emergence of high heat-flux electronic components [4]. The overall heat transfer coefficient of the spray impingement cooling systems depends on the contact time and flow dynamics of the impacting drops. The efficiency of the spray cooling system relies on continuous removal of impinged droplets and optimum contact time of the drop. The flow dynamics and contact time of drops depend on the wettability of the surface and can be engineered either by a manipulation of surface textures, chemical treatment (coating) or a combination of both
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