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PHOTOGALLERY

Visualization of Dropwise Condensation on a Superhydrophobic Microporous Surface

[+] Author and Article Information
Jin Sub Kim

Department of Energy Conversion Systems, Korea Institute of Machinery and Materials, Daejeon 34103, Korea
jskim129@kimm.re.kr

Dong Hwan Shin

Department of Energy Conversion Systems, Korea Institute of Machinery and Materials, Daejeon 34103, Korea
dhshin@kimm.re.kr

Wooyong Moon

Mechanical Design Group, Hanwha Systems, 491-23, Gyeonggidong-ro, Namsa-myun, Cheoin-gu, Yongin 17121, Korea
Wooyong.moon@hanwha.com

Jaehun Heo

Mechanical Design Group, Hanwha Systems, 491-23, Gyeonggidong-ro, Namsa-myun, Cheoin-gu, Yongin 17121, Korea
jh77.heo@hanwha.com

Jungho Lee

Department of Energy Conversion Systems, Korea Institute of Machinery and Materials, Daejeon 34103, Korea
jungho@kimm.re.kr

1Corresponding author.

ASME doi:10.1115/1.4040395 History: Received April 30, 2018; Revised May 09, 2018

Abstract

Condensation behavior on a superhydrophobic microporous surface was visually compared with that on a plain surface in the water saturated at the pressures of 101.3 kPa (Tsat = 100 °C) and 3.2 kPa (Tsat = 25 °C). The microporous surface was formed by sintering copper powders with the average diameter of 50 µm on the bare copper surface, resulting in the coating thickness of approximately 250 µm. The microporous surface was coated with the polytetrafluoroethylene (PTFE) layer by the spray-coating method to change the wettability into superhydrophobic, which was verified from a measured apparent contact angle of above 150°. While dropwise condensation is observed on both bare and hydrophobic plain surfaces at Psat = 101.3 kPa, filmwise condensation is seen on the superhydrophilic plain surface. At the low saturation pressure of 3.2 kPa, condensation behavior on the bare plain surface is changed into the filmwise condensation with improved wettability. In contrast, on the microporous surface, the only superhydrophobic microporous surface shows dropwise condensation behavior, where the surface is considered at the Cassie-state. However, filmwise condensation behaviors are observed on both superhydrophilic and bare microporous surfaces due to the wicking into the pores.

Copyright (c) 2018 by ASME
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