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Boiling heat transfer enhancement on titanium through nucleation-promoting morphology and tailored wettability
ID Može, Matic (Avtor), ID Hadžić, Armin (Avtor), ID Zupančič, Matevž (Avtor), ID Golobič, Iztok (Avtor)

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Izvleček
Surface engineering aimed at tuning the wettability and morphology of the boiling surface is a facile approach to moderate and enhance the nucleate boiling process. Key issues include control over the active nucleation site density, bubble departure frequency and liquid replenishment of active nucleation sites while simultaneously reducing the bubble nucleation temperature. In this study, we fabricated spear-type (ST) and cavity-type (CT) TiO$_2$ nanostructures on 25 μm titanium foils via hydrothermal etching in an alkaline solution. High-speed IR and video cameras were used to detect local phenomena in terms of temperature and heat flux fluctuations and observe the bubble dynamics during saturated pool boiling of water. Intrinsically hydrophilic ST and CT surfaces provided a moderate overall enhancement of the heat transfer coefficient compared to an untreated surface due to increased nucleation site density and bubble frequency. The CT surface also decreased the bubble nucleation temperature due to effective vapor-entrapping and nucleation-promoting cavities. In a further step, both surfaces were hydrophobized through chemical vapor deposition of a fluorinated silane to tailor the wettability of the surface into a superhydrophobic state. This further reduced the average surface superheat by at least 40%, while the nucleation frequencies exceeded 200 Hz on the hydrophobized CT surface. In comparison with the untreated reference surface, the heat transfer coefficient on hydrophobized ST and CT surfaces was enhanced by 89% and 237% at 100 kW m$^{−2}$, respectively. Moreover, the full width at half maximum (FWHM) value of the surface temperature distribution was reduced by 73% and 95% at the same heat flux, respectively. The study confirms that hydrophobic surface treatment can significantly enhance the nucleate boiling process when combined with an appropriate surface structure. Despite the affinity between the vapor and the hydrophobic layer, the cavity-type and spear-type TiO$_2$ structures are able to maintain active nucleation sites well-separated, which prevents the undesirable vapor spreading that possibly leads to an early onset of critical heat flux.

Jezik:Angleški jezik
Ključne besede:pool boiling, heat transfer enhancement, IR thermography, titanium nanostructures, hydrophobicity, functionalized surfaces
Vrsta gradiva:Članek v reviji
Tipologija:1.01 - Izvirni znanstveni članek
Organizacija:FS - Fakulteta za strojništvo
Status publikacije:Objavljeno
Različica publikacije:Objavljena publikacija
Leto izida:2022
Št. strani:17 str.
Številčenje:Vol. 195, art. 123161
PID:20.500.12556/RUL-137561 Povezava se odpre v novem oknu
UDK:536.24
ISSN pri članku:0017-9310
DOI:10.1016/j.ijheatmasstransfer.2022.123161 Povezava se odpre v novem oknu
COBISS.SI-ID:112393987 Povezava se odpre v novem oknu
Datum objave v RUL:22.06.2022
Število ogledov:625
Število prenosov:123
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Gradivo je del revije

Naslov:International journal of heat and mass transfer
Skrajšan naslov:Int. j. heat mass transfer
Založnik:Elsevier
ISSN:0017-9310
COBISS.SI-ID:3064335 Povezava se odpre v novem oknu

Licence

Licenca:CC BY 4.0, Creative Commons Priznanje avtorstva 4.0 Mednarodna
Povezava:http://creativecommons.org/licenses/by/4.0/deed.sl
Opis:To je standardna licenca Creative Commons, ki daje uporabnikom največ možnosti za nadaljnjo uporabo dela, pri čemer morajo navesti avtorja.

Sekundarni jezik

Jezik:Slovenski jezik
Ključne besede:vrenje v bazenu, izboljšan prenos toplote, IR termografija, titanove nanostrukture, hidrofobnost, funkcionalizirane površine

Projekti

Financer:ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
Številka projekta:P2-0223
Naslov:Prenos toplote in snovi

Financer:ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
Številka projekta:J2-2486
Naslov:Izboljšan prenos toplote pri vrenju z uporabo hierarhičnih funkcionaliziranih površin (eHEATs)

Financer:ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
Številka projekta:N2-0251
Naslov:Izboljšanje procesa vrenja z uporabo teksturiranih površin (BEST)

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