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Enhanced pool-boiling heat transfer on laser-made hydrophobic/superhydrophilic polydimethylsiloxane-silica patterned surfaces
Zupančič, Matevž (Author), Steinbücher, Miha (Author), Gregorčič, Peter (Author), Golobič, Iztok (Author)

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Abstract
This study presents the application of hydrophobic polydimethylsiloxane-silica coating used for the development of biphilic surfaces that are designed to enhance the heat transfer during boiling. Surface analyses showed that this coating exhibits a high hydrophobicity due to its hierarchical structure and the use of hydrophobic polymer. An appropriate thermal treatment leads to the oxidation of the methyl groups and a formation of silicon oxide and silicon carbide that result in a wettability transition from hydrophobic to superhydrophilic. On this basis, we manufactured hydrophobic/superhydrophilic patterns on stainless-steel foils using a pulsed Nd:YAG laser. The uniform, superhydrophilic surface exhibited a 350% larger critical heat flux (CHF) than bare stainless-steel foil. High-speed IR thermography revealed that the increased wettability reduced the bubble contact diameter, allowed a higher density of active nucleation sites, and delayed the dry-out. The biphilic surfaces with differently sized hydrophobic spots exhibited the highest heat transfer coefficients, with an up to 200% higher CHF compared to the bare stainless steel. Smaller hydrophobic spots reduced the bubble diameter and increased the nucleation frequency. However, surfaces with larger hydrophobic regions promoted boiling incipience and exhibited higher heat transfer coefficients at low heat fluxes. These results suggest that the optimal biphilic pattern could only be determined for a particular operating point. Our data provide a new insight into the complex phenomena of nucleate pool boiling on chemically and mechanically heterogeneous surfaces.

Language:English
Keywords:pool boiling, heat transfer enhancement, biphilic micropattern, laser-processed surface, high-speed IR thermography, polydimethylsiloxane-silica coating
Work type:Article (dk_c)
Tipology:1.01 - Original Scientific Article
Organization:FS - Faculty of Mechanical Engineering
Year:2015
Number of pages:str. 288-297
Numbering:Vol. 91
UDC:536.24(045)
ISSN on article:1359-4311
DOI:10.1016/j.applthermaleng.2015.08.026 Link is opened in a new window
COBISS.SI-ID:14131227 Link is opened in a new window
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Downloads:365
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Record is a part of a journal

Title:Applied Thermal Engineering
Shortened title:Appl. therm. eng.
Publisher:Elsevier Science
ISSN:1359-4311
COBISS.SI-ID:1861910 This link opens in a new window

Document is financed by a project

Funder:ARRS - Agencija za raziskovalno dejavnost Republike Slovenije (ARRS)
Project no.:P2-0392
Name:Optodinamika

Secondary language

Language:Slovenian
Keywords:vrenje v bazenu, izboljšan prenos toplote, bifilne mikro strukture, lasersko procesirane površine, hitrotekoča IR termografija, polidimetilsiloksan-silika premaz

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