Article
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Dropwise Condensation Mechanism on Smooth Hydrophilic Surfaces
Version 1
: Received: 25 August 2021 / Approved: 30 August 2021 / Online: 30 August 2021 (10:12:38 CEST)
A peer-reviewed article of this Preprint also exists.
Bayani Ahangar, S.; Lee, K.-B.; Choi, C.K. Dropwise Condensation Mechanism on Smooth Hydrophilic Surfaces. Appl. Sci. 2021, 11, 9184. Bayani Ahangar, S.; Lee, K.-B.; Choi, C.K. Dropwise Condensation Mechanism on Smooth Hydrophilic Surfaces. Appl. Sci. 2021, 11, 9184.
Abstract
The objective of this work is to identify the mechanism of dropwise condensation on a smooth solid surface. We investigate the stable dropwise condensation that occurs at a droplet growth rate of 1 µm/s in diameter on a gold-coated glass surface. Additionally, we present our observations on unstable dropwise condensation, i.e., degradation of dropwise condensation of steam on a gold surface. The Surface Plasmon Resonance Imaging (SPRi) approach used in this study has lateral resolutions of 4-10 µm, thickness resolutions of 0.1-1 nm, and temporal resolutions of 200-10,000 frames per second (FPS). SPRi is used to evaluate the existence and structure of thin films and occurrence of initial nuclei during condensation. Visualization of the onset of stable dropwise condensation suggests droplets form at heterogeneous nucleation sites and that no film greater than a monolayer exists on the surface before the formation of droplets. Observation of the unstable dropwise condensation of steam shows the existence of water films that are several nanometers thick between droplets. This work shows that neither the nucleation theory or film rupture theory can individually explain the physics of dropwise condensation. Therefore, there is a need for a more comprehensive theory that can explain the mechanism of dropwise condensation.
Keywords
surface plasmon resonance; thin film; dropwise condensation; monolayer; dropwise condensation mechanism; nucleation; film rupture theory; degradation of dropwise condensation
Subject
Physical Sciences, Fluids and Plasmas Physics
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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