Capillary evaporation on micromembrane-enhanced microchannel wicks with atomic layer deposited silica

Dai, Xianming; Famouri, M.; Абдулагатов, А. И.; Yang, Ronggui; Lee, Yung-Cheng; George, Steven M.; Li, Chen

doi:10.1063/1.4824439

Cited by 45 publications

(20 citation statements)

References 33 publications

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“…Hybrid wick structures that can combine the strengths of these two types of wick structures are highly desirable to achieve high performance heat pipes in terms of effective thermal conductivity as well as working load. Powder-groove wick and mesh-groove wick are two types of hybrid wicks developed to enhance heat pipe performance [9][10][11]. The mesh-groove wick with relatively higher permeability is favorable to reduce the flow resistance, particularly, with the assistance of gravity.…”

Section: Introductionmentioning

confidence: 99%

A New Approach for Thermo-Fluid Behavior through Porous Layer of Heat Pipes

Nouri-Borujerdi

2017

Scientia Iranica

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This paper developed a new mathematical model to investigate the heat transfer as well as wick thickness of a heat pipe. The model was set up by conservative equations of continuity, momentum and energy in the thermal boundary layer. Using the similarity variable, the governing equations have been changed to a set of ordinary differential equations and they were solved numerically by the forth order Runge-Kutta method. The flow variables such as velocity components, wick thickness and Nusselt number were obtained. The results show that the Nusselt number is proportional to the root square root of the Darcymodified Rayleigh number and that the distance from the edge of the condenser surface. Furthermore, the thickness of the wick material depends on the Jakob number and proportional to the heat transfer between the wall and the liquid film.

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Section: Introductionmentioning

confidence: 99%

A New Approach for Thermo-Fluid Behavior through Porous Layer of Heat Pipes

Nouri-Borujerdi

2017

Scientia Iranica

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“…Superhydrophilic ALD SiO 2 coatings are also incapable of improving CHF because the enhanced capillary force is balanced by the increased flow friction as shown in our previous study. 17 However, the biphilic nonporous coatings can increase CHF to 171.7 W/ cm 2 from 151.7 W/cm 2 on the bare MEMs (Fig. 4(b)).…”

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confidence: 99%

“…The conformal superhydrophilic ALD SiO 2 coatings can enhance wetting conditions and thin film evaporation as demonstrated in our earlier work. 17 Even though the 80 nmthick biphilic nanoporous surface provide more nucleate cavities than the conformal ALD coatings, it still underperforms ALD SiO 2 coatings due to the additional thermal resistance (Figs. 4(c) and 4(e)).…”

mentioning

confidence: 99%

“…Superhydrophilic surfaces can promote nucleate boiling and thin film evaporation through augmenting the wetting areas. 17,18 However, hydrophilic surfaces can induce higher flow resistance because of the induced non-slip boundary conditions owing to the complete wetting characteristics when compared to hydrophobic ones. Additionally, bubble departure on the hydrophilic surfaces can be retarded by the high pinning forces on the contact line and the nucleation cavities suffer from flooding.…”

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confidence: 99%

“…4(b)), which is an increase of 53.4% over the bare MEMs because of the enhanced thin film evaporation resulting from the the superhydrophilic ALD SiO 2 coatings. 17 The intrinsically hydrophobic MWCNTs augmented the nucleation site density and surface areas, yielding enhanced nucleate boiling and thin film evaporation. Not surprisingly, the poor wettability substantially reduced CHF.…”

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confidence: 99%

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Biphilic nanoporous surfaces enabled exceptional drag reduction and capillary evaporation enhancement

Dai

Yang

et al. 2014

Applied Physics Letters

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Simultaneously achieving drag reduction and capillary evaporation enhancement is highly desired but challenging because of the trade-off between two distinct hydrophobic and hydrophilic wettabilities. Here, we report a strategy to synthesize nanoscale biphilic surfaces to endow exceptional drag reduction through creating a unique slip boundary condition and fast capillary wetting by inducing nanoscopic hydrophilic areas. The biphilic nanoporous surfaces are synthesized by decorating hydrophilic functional groups on hydrophobic pristine multiwalled carbon nanotubes. We demonstrate that the carbon nanotube-enabled biphilic nanoporous surfaces lead to a 63.1% reduction of the friction coefficient, a 61.7% wetting speed improvement, and up to 158.6% enhancement of capillary evaporation heat transfer coefficient. A peak evaporation heat transfer coefficient of 21.2 W/(cm2·K) is achieved on the biphilic surfaces in a vertical direction.

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Thin Film Condensation on Nanostructured Surfaces

Zhang

Shetty

et al. 2018

Adv Funct Materials

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Water vapor condensation is a ubiquitous process in nature and industry. Over the past century, methods achieving dropwise condensation using a thin (<1 µm) hydrophobic 'promoter' layer have been developed, which increases the condensation heat transfer by 10 times compared to filmwise condensation. Unfortunately, implementations of dropwise condensation have been limited due to poor durability of the promoter coatings. Here, we develop thin film condensation which utilizes a promoter layer not as a condensation surface, but rather to confine the condensate within a porous biphilic nanostructure, nickel inverse opals (NIO) with a thin (<20 nm) hydrophobic top-layer of decomposed polyimide. We demonstrate filmwise condensation confined to thicknesses <10 µm. To test the stability of thin film condensation, we performed condensation experiments to show that at higher supersaturations (0.975 < S < 2.05), droplets coalescing on top of the hydrophobic layer are absorbed into the superhydrophilic layer through coalescence induced transitions. Through detailed This article is protected by copyright. All rights reserved.3 thermal-hydrodynamic modeling, we show that thin film condensation has the potential to achieve heat transfer coefficients approaching ≈100 kW m -2 while avoiding durability issues by significantly reducing nucleation on the hydrophobic surface. The work presented here develops an approach to potentially ensure durable and high performance condensation comparable to dropwise condensation.

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Capillary evaporation on micromembrane-enhanced microchannel wicks with atomic layer deposited silica

Cited by 45 publications

References 33 publications

A New Approach for Thermo-Fluid Behavior through Porous Layer of Heat Pipes

A New Approach for Thermo-Fluid Behavior through Porous Layer of Heat Pipes

Biphilic nanoporous surfaces enabled exceptional drag reduction and capillary evaporation enhancement

Thin Film Condensation on Nanostructured Surfaces

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