Biphilic nanoporous surfaces enabled exceptional drag reduction and capillary evaporation enhancement

Dai, Xianming; Yang, Fanghao; Yang, Ronggui; Huang, Xinyu; Rigdon, William A.; Li, Xiaodong; Li, Chen

doi:10.1063/1.4901962

Cited by 32 publications

(7 citation statements)

References 27 publications

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“…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%

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: 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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“…Besides, they can also provide large capillary force to continuously pump liquid to the interface for vaporization. Thus, they are extensively applied in evaporation studies to minimize the thermal resistance of the system and enhance liquid supply [28][29][30][31]. However, these micro/nanostructures, usually with a porous geometry, induce large viscous resistance for fluid transport to the interface, which is dictated by the pore size and coupled with the pumping capillary force.…”

Section: Introductionmentioning

confidence: 99%

Transition between thin film boiling and evaporation on nanoporous membranes near the kinetic limit

Wang

Shi

Chen

2020

International Journal of Heat and Mass Transfer

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Nanoporous structures including single nanopores and nanoporous membranes have beenutilized as a platform to study fundamental liquid-vapor phase change heat transfer (PCHT) processes as well as a promising candidate for high flux heat dissipation. Previously, we implemented nanoporous membranes to support a thin liquid film for boiling, which was termed "thin film boiling", and realized high heat transfer performance. Besides thin film boiling, thin film evaporation through nanoporous structures have also been demonstrated to achieve high heat flux, but these two mechanisms are usually considered two mutually exclusive regimes operated under vastly different conditions, and the factors dictating how close the PCHT process is to the kinetic limit are elusive. In this work, we utilized a unique transition between thin film boiling and evaporation through nanoporous membranes to clarify the factors determining the heat flux and heat transfer coefficient (HTC) with respect to the kinetic limit conditions. We unambiguously showed the controllable transition from boiling to evaporation, when the liquid receded into the nanopores and provided additional driving force from capillary pumping sustained in the nanoscale pores. We showed that this transition is universal and can be understood from a simple fluid transport model for all the four types of fluids we studied, which cover a wide span of surface tension (water, ethanol, IPA, FC-72). More importantly, PCHT conditions at the transition points between boiling and evaporation were close to those of the kinetic limit of all these fluids. However, further increase of the heat flux beyond the transition points led to decreasing HTC and deviation from the kinetic limit, which can be attributed to the increasing vapor resistance in the vapor space and inside the nanopores. This increasing vapor resistance was also confirmed by experiments on IPA with different vapor pressures. Our work could shed light on PCHT on nanoporous structures with respect to the kinetic limit, and could advance the development of high heat-flux heat dissipation devices, especially using dielectric fluids.

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“…The CHF of nanoporous surface increases with increasing Δ P , which can be explained by the limiting mechanism for CHF in the current configuration. In some of the boiling experiments on micro- or nanostructures, the capillary limit is the ultimate limit for the CHF condition. − Liquid–vapor interfaces confined in these structures generate large capillary force which drives the liquid to the phase-change sites and the CHF is achieved when the capillary driving pressure is balanced by the viscous drag of liquid transport. However, in our current configuration the membrane was always covered by the liquid, and there was no meniscus liquid–vapor interface inside the nanopores of the AAO membrane.…”

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confidence: 99%

Ultrahigh Flux Thin Film Boiling Heat Transfer Through Nanoporous Membranes

Wang

Chen

2018

Nano Lett.

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Phase change heat transfer is fundamentally important for thermal energy conversion and management, such as in electronics with power density over 1 kW/cm. The critical heat flux (CHF) of phase change heat transfer, either evaporation or boiling, is limited by vapor flux from the liquid-vapor interface, known as the upper limit of heat flux. This limit could in theory be greater than 1 kW/cm on a planar surface, but its experimental realization has remained elusive. Here, we utilized nanoporous membranes to realize a new "thin film boiling" regime that resulted in an unprecedentedly high CHF of over 1.2 kW/cm on a planar surface, which is within a factor of 4 of the theoretical limit, and can be increased to a higher value if mechanical strength of the membranes can be improved (demonstrated with 1.85 kW/cm CHF in this work). The liquid supply is achieved through a simple nanoporous membrane that supports the liquid film where its thickness automatically decreases as heat flux increases. The thin film configuration reduces the conductive thermal resistance, leads to high frequency bubble departure, and provides separate liquid-vapor pathways, therefore significantly enhances the heat transfer. Our work provides a new nanostructuring approach to achieve ultrahigh heat flux in phase change heat transfer and will benefit both theoretical understanding and application in thermal management of high power devices of boiling heat transfer.

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Biphilic nanoporous surfaces enabled exceptional drag reduction and capillary evaporation enhancement

Cited by 32 publications

References 27 publications

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

Transition between thin film boiling and evaporation on nanoporous membranes near the kinetic limit

Ultrahigh Flux Thin Film Boiling Heat Transfer Through Nanoporous Membranes

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