Dataset Information

Coalescence-Induced Jumping of Multiple Condensate Droplets on Hierarchical Superhydrophobic Surfaces.

ABSTRACT: Coalescence-induced jumping of condensate droplets from a superhydrophobic surface with hierarchical micro/nanoscale roughness is quantitatively characterized. Experimental observations show that the condensate droplet jumping is induced by coalescence of multiple droplets of different sizes, and that the coalesced droplet trajectories typically deviate from the surface normal. A depth-from-defocus image processing technique is developed to track the out-of-plane displacement of the jumping droplets, so as to accurately measure the droplet size and velocity. The results demonstrate that the highest jumping velocity is achieved when two droplets coalesce. The jumping velocity decreases gradually with an increase in the number of coalescing droplets, despite the greater potential surface energy released upon coalescence. A general theoretical model that accounts for viscous dissipation, surface adhesion, line tension, the initial droplet wetting states, and the number and sizes of the coalescing droplets is developed to explain the trends of droplet jumping velocity observed in the experiments.

SUBMITTER: Chen X

PROVIDER: S-EPMC4698694 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Publications

Coalescence-Induced Jumping of Multiple Condensate Droplets on Hierarchical Superhydrophobic Surfaces.

Chen Xuemei X Patel Ravi S RS Weibel Justin A JA Garimella Suresh V SV

Scientific reports 20160104

Coalescence-induced jumping of condensate droplets from a superhydrophobic surface with hierarchical micro/nanoscale roughness is quantitatively characterized. Experimental observations show that the condensate droplet jumping is induced by coalescence of multiple droplets of different sizes, and that the coalesced droplet trajectories typically deviate from the surface normal. A depth-from-defocus image processing technique is developed to track the out-of-plane displacement of the jumping drop ...[more]

PMID: 26725512

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Project description:Coalescence-induced condensate droplet jumping from superhydrophobic surfaces can be exploited in condensation heat-transfer enhancement, imparting self-cleaning behavior to surfaces, anti-icing coatings, and other industrial uses. An intriguing application would exploit this phenomenon to achieve thermal rectification using a sealed vapor chamber with opposing superhydrophilic and superhydrophobic surfaces. During forward operation, continuous evaporation occurs from the heated superhydrophilic evaporator surface; self-propelled jumping returns the condensate droplets from the cooler superhydrophobic surface to the evaporator, allowing passive recirculation of the working fluid without a reliance on gravity or capillary wicking for fluid return. In reverse operation, when the superhydrophobic surface is heated, the absence of a mechanism for fluid return from the cooler superhydrophilic side to the evaporator restricts heat transport across the (low conductivity) vapor gap. The effectiveness of this jumping-droplet thermal diode can be enhanced by maximizing the distance between the opposing superhydrophobic and superhydrophilic surfaces. It is, therefore, important to investigate the height to which the condensate droplets jump from the superhydrophobic surfaces such that replenishment of liquid to the superhydrophilic surface is maintained. In this study, we systematically investigate the height to which the condensate droplets jump from the hierarchical superhydrophobic surfaces having truncated microcones coated with nanostructures. The condensate droplet jumping height increases with a decrease in microcone pitch. A general theoretical model that accounts for surface adhesion, line tension, and initial wetting states of multiple coalescing droplets of different radii is used to predict and explain the experimentally observed trend of droplet jumping height with surface roughness. The insights provided regarding the effect of surface topography on droplet jumping height are critical to the design of high-performance thermal diode devices.

Dataset Information

Coalescence-Induced Jumping of Multiple Condensate Droplets on Hierarchical Superhydrophobic Surfaces.

Publications

Coalescence-Induced Jumping of Multiple Condensate Droplets on Hierarchical Superhydrophobic Surfaces.

Similar Datasets

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