Influence of surface modification on droplet mobility during dropwise condensation

Abstract

AbstractA two‐step surface fabrication technique is used to modify the wetting characteristics of copper sheets for heat transfer application. It consists of oxygen plasma treatment that results in the formation of surface nanostructures, and a post‐functionalization process using self‐assembled monolayers. The copper samples are characterized by contact angle measurements, scanning electron microscopy, and atomic force microscopy. Results show that surface roughness, described using hybrid and functional roughness parameters, varies with irradiation power. The plasma‐treated copper samples become superhydrophobic with water contact angles ranging from 150° to 160° after the post‐functionalization. Condensation experiments are conducted to explore the influence of surface wettability on condensate formation. Results show that droplets formed on the superhydrophobic copper sheets are smaller and more mobile with sweep events that are 9x more frequent compared to those on untreated copper sheets. Sweep events are shown to be influenced by surface porosity, which is defined using standard roughness parameters. It is demonstrated that higher surface porosity results to higher sweep interval.