Induced liquid-solid contact via micro/nano multiscale texture on a surface and its effect on the Leidenfrost temperature

• Published in: Experimental thermal and fluid science Vol. 84; pp. 156 - 164
• Main Authors: Lee, Gi Cheol, Kang, Jun-young, Park, Hyun Sun, Moriyama, Kiyofumi, Kim, Seol Ha, Kim, Moo Hwan
• Format: Journal Article
• Language: English
• Published: Philadelphia Elsevier Inc 01-06-2017; Elsevier Science Ltd
• Subjects: Anodizing; Contact angle; Droplet rebound; High speed photography; High temperature; Induced liquid-solid contact; Leidenfrost temperature (LFT); Liquid precursor; Mechanical polishing; Micro roughness; Micro/nano multiscale texture; Needles; Oxidation; Photography; Roughness; Surface layers; Surface roughness; Temperature; Temperature effects; Texture; Water drops; Wetting front; Liquid precursor; Micro/nano multiscale texture; Induced liquid-solid contact; Leidenfrost temperature (LFT); Droplet rebound; Micro roughness
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2017.01.022

•Heat transfer performance of a droplet on modified surface is evaluated.•Micro/nano multiscale textured surface (MTS) shows a super-hydrophilic property.•MTS affects to increase of Leidenfrost temperature up to 465°C.•The precursor wetting front was observed on MTS, initially heated over than 400°C.
A significant increase in the Leidenfrost temperature (LFT) was observed on a micro/nano multiscale textured surface (MTS) compared with a polished surface (PS) and a micro rough surface (MRS). MTS was fabricated by anodic oxidation and has nano-scaled needles with micro roughness. It showed improved surface wetting characteristics (0° contact angle with liquid spreading). On the other hand, MRS was fabricated by mechanical polishing and it only has micro roughness. LFT on MTS and MRS increased by approximately 150°C and 30°C, respectively, compared with one for PS. The textures on each surface influenced the water droplet dynamics. The relationship between LFT and the dynamics of water droplet were studied by high-speed photography. The key phenomenon determining LFT was the rebound process of the droplet during a few milliseconds. On MRS and MTS, the rebound phenomenon of the droplet was disturbed by the surface-texture-induced liquid-solid contact even when the surface was initially at a high temperature over 300°C. The precursor wetting front, observed only on MTS and the capillary wicking phenomenon are likely the responsible mechanisms that significantly increased LFT on MTS.