Experimental investigation of water droplet impact and icing on hydrophobic surfaces with varying wettabilities

Pan, Yuntao (2018) Experimental investigation of water droplet impact and icing on hydrophobic surfaces with varying wettabilities. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (2MB)

Abstract

Ice formation and accumulation can lead to operational failure and risks for structures such as power transmission lines, aircrafts, offshore platforms, marine vessels and wind turbines. Liquid repellent surfaces could reduce ice accretion and improve asset integrity and safety in harsh environments. there are significant needs to probe how surface wettability affects the droplet impact, ice formation and ice accretion processes. This study presents experimental results of water droplet impact, droplet dynamics, and icing delay time on flat and inclined stainless-steel surfaces with varying wettabilities. Several different designs of the micro-structure of the hydrophobic surfaces are considered. The commercial hydrophobic coating from Aculon is also used to improve liquid repellency and reduce ice accumulation. It was found that the impact speed and surface wettability are significant factors to the droplet oscillation and the total icing time. The droplet oscillation time is significantly longer on a hydrophobic surface than on a hydrophilic one. Lower surface wettability also significantly increases the droplet total icing time. The droplet total icing time decreases with lower droplet temperature, larger droplet impact velocity, and smaller droplet diameter. The droplet shows a gliding phase on an inclined surface. The total icing time decreases on the inclined surface since the contact area increases due to the gliding process. for typical droplet icing process, the ice formation initiates at the solid-liquid interface and then propagates from bottom to top through the liquid-gas interface. The droplet bounces off from the angled superhydrophobic surface made by electrodeposition at room temperature.

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