The effect of water absorption on critical heat flux enhancement during pool boiling

Ahn, Ho Seon; Park, Gunyeop; Kim, Ji Min; Kim, Joonwon; Kim, Moo Hwan

doi:10.1016/j.expthermflusci.2012.05.005

Cited by 96 publications

(65 citation statements)

References 15 publications

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“…This enhancement in CHF can be attributed to a variety of mechanisms, including increased nucleation site densities [1,5,15], elongated contact line [7,16], enhanced micro-convection around nucleated bubbles [4,17,18], increased bubble departure frequency [19], and enhanced microlayer evaporation via a strong wicking effect [3,9,13,14,[20][21][22]. Among these possible mechanisms, the enhanced microlayer evaporation through wicking has been widely accepted as the dominant mechanism, where correlations [3,21] and theoretical predictions [22] have been established between the CHF and the wicking rate.…”

Section: Introductionmentioning

confidence: 93%

“…Recent efforts using micro/nanostructured and hierarchical structured surfaces to enhance heat transfer coefficient (HTC) and CHF of boiling experiments have resulted in enhanced CHF on the order of 200-313 W/cm 2 [1,[3][4][5][6][7][8][9][10][11][12][13][14]. This enhancement in CHF can be attributed to a variety of mechanisms, including increased nucleation site densities [1,5,15], elongated contact line [7,16], enhanced micro-convection around nucleated bubbles [4,17,18], increased bubble departure frequency [19], and enhanced microlayer evaporation via a strong wicking effect [3,9,13,14,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Sun

2016

International Journal of Heat and Mass Transfer

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a b s t r a c tThe effect of nanostructures on heat transfer coefficient of an evaporating meniscus in thin film evaporation and nucleate boiling is investigated using combined modeling and molecular dynamics (MD) simulations. The model is developed accounting for the evaporation kinetics, disjoining pressure, conduction resistance, and Kapitza resistance of an evaporating meniscus on a nanostructured surface. The model is then verified using MD simulations for a water-gold system with square nanostructures of varying depth and film thickness. Good agreement is obtained between MD results and model predictions. The results show the existence of a critical film thickness on the order of a few nanometers where the heat transfer coefficient reaches its maximum. For a film thickness below this critical value, the evaporation resistance dominates and the heat transfer coefficient increases with film thickness but decreases with nanostructure depth due to the enhanced disjoining pressure. However, for a film thickness greater than the critical value, the conduction resistance dominates and the heat transfer coefficient decreases with film thickness but increases with nanostructure depth. In addition, both critical film thickness and maximum heat transfer coefficient increase with the roughness ratio of the nanostructure, mainly due to the reduction in Kapitza resistance.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Sun

2016

International Journal of Heat and Mass Transfer

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“…Equation (9) was used to fit the friction dominant stage, and the fitted curves are shown in Fig. 9.…”

Section: Resultsmentioning

confidence: 99%

“…Wettability, which is the property of transform between solid-gas interface and solid-liquid interface, is one of the important properties of micro-/nanoporous metals. By affecting water and gas management, the wettability of micro-/nanoporous metals plays a significant role in their applications, such as enhancing boiling heat transfer [7][8][9][10], capillary pumped loops [11] and fuel cells [4]. One of wellknown and effective methods to measure wettability of solid surface is in terms of static contact angle.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, these methods studied the wetting process of porous media only from a single view, which results in incomplete information. For example, for both capillary rise test method, which studies the capillaries of porous media by measuring the liquid rise rate and height, and droplet spreading test method, which analyzes the motions of the precursor rim and the contact line of a droplet, information about spreading of liquid on top of the porous structure (surface spreading), which plays an important role in various applications of porous metals, such as enhancing boiling heat transfer [7][8][9][10] and self-cleaning surface [16], could not be described clearly. In addition, for droplet imbibition test method, which analyzes the motion of the penetration depth of a droplet through the measurement of the droplet cap above the surface, the information about spreading of liquid inside porous structure (internal spreading), which is an important property for fuel cells [4] and heat pipes [11], could not be characterized.…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation on wetting process of water droplets on micro-/nanoporous copper films

Miao

et al. 2015

Appl. Phys. A

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In this paper, the dynamics of contact angle and droplet spreading were combined to study wetting process of droplet on porous media, revealing comprehensive information about surface spreading and internal spreading of the droplet. To precisely locate the precursor rim in the droplet spreading test, background subtraction method was proposed for use in visualizing the precursor rim. Two types of micro-/nanoporous copper films fabricated by an electrochemical deposition method were tested. The results indicated that contact angle of the micro-/nanoporous copper films decreased with time quickly and became 0°at last, which is a result of surface spreading combined with down-absorption. The dynamic of precursor rim velocity which can reflect the kinetics of internal spreading was divided into three stages: friction dominant stage, balance stage and exhausting stage. In the friction dominant stage, the velocity of precursor rim can be described by an exponential law, while the velocity of precursor rim in balance stage, which is only affected by the internal characteristics of porous media, was proposed to compare internal wettability of porous media.

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Enhanced Capillary‐Fed Boiling in Copper Inverse Opals via Template Sintering

Zhang

Palko

Barako

et al. 2018

Adv Funct Materials

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Capillary-fed boiling of water from microporous metal surfaces is promising for low thermal resistance vapor chamber heat spreaders for hot spot management. Vapor transport through the void spaces in porous metals enables high heat fluxes at low evaporator superheat. In this work, the critical heat fluxes of capillary-fed boiling in copper inverse opal (IO) wicks that consist of uniform pores with 3D periodicity is investigated. Template sintering is used to enlarge the "necks", or hydraulic vias, that bridge adjacent IO pores of diameters from 0.6 to 2.1 µm. The enhanced neck size increases the hydraulic permeability for vapor extraction by an order of magnitude, and subsequently the CHF from 100 to 1100 W cm −2 . Modeling of the boiling limit accounts for the vapor pressure drop through an IO wick using Darcy's law at a given bubble departure rate. This work links the effect of wick structure design on the boiling crises phenomenon in microporous surfaces and demonstrates material capabilities for ultrathin and low superheat thermal management solutions for high-power-density electronic devices.

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The effect of water absorption on critical heat flux enhancement during pool boiling

Cited by 96 publications

References 15 publications

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Experimental investigation on wetting process of water droplets on micro-/nanoporous copper films

Enhanced Capillary‐Fed Boiling in Copper Inverse Opals via Template Sintering

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