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Heat transfer suppression by suspended droplets on microstructured surfaces

Authors :
Evelyn N. Wang
Mengyao Wei
Yangying Zhu
Chuan Seng Tan
Daniel J. Preston
Youngsup Song
Source :
Applied Physics Letters. 116:233703
Publication Year :
2020
Publisher :
AIP Publishing, 2020.

Abstract

Manipulating the degree of droplet contact with a surface significantly impacts applications involving drag reduction, corrosion inhibition, droplet transportation, and thermal management. Extensive studies have been conducted to study droplet wetting behavior on plain and micro/nanostructured surfaces, with a particular focus in the recent literature on heated surfaces, where evaporation beneath the droplet impacts the apparent wettability. In previous literature, the peak droplet lifetime and minimum heat transfer on heated surfaces were observed at the Leidenfrost point. In this study, however, we report the existence of two distinct peaks for droplet lifetime on heated surfaces structured with silicon micropillar arrays. Initially, droplets exhibit complete wetting at low surface temperatures, but as surface temperature increases, the wetting state transitions first to a contact non-wetting state (i.e., a Cassie–Baxter-like state) and then to the non-contact Leidenfrost state; two distinct local maxima in droplet lifetime are observed, one corresponding to each transition. The contact non-wetting transition temperature and Leidenfrost point increase with larger micropillar pitch and taller height, which we attribute primarily to the resulting lower effective thermal conductivity of the micropillar array beneath the droplets, in agreement with the analytical force-balance-based modeling. This study provides a comprehensive investigation of the effect of surface structuring on contact non-wetting and Leidenfrost phenomena and will serve as design guidelines in controlling the contact non-wetting and Leidenfrost temperatures for specific applications.

Details

ISSN :
10773118 and 00036951
Volume :
116
Database :
OpenAIRE
Journal :
Applied Physics Letters
Accession number :
edsair.doi...........708b7306e5f7cb1906e58f2f4877680e
Full Text :
https://doi.org/10.1063/5.0010510