On the Size Range of Active Nucleation Cavities on a Heating Surface

Hsu, Y. Y.

doi:10.1115/1.3684339

Cited by 785 publications

(259 citation statements)

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“…Several mechanisms that result in sustained evaporation from capillary-fed structures have been proposed. The classical model of Hsu [84]recognizes that the required incipience superheat is based on a limiting thermal boundary layer thickness in the superheated liquid. This model is widely used to understand the nucleation process and agrees with experimental trends for pool boiling.…”

Section: Incipience Of Boiling Under Capillary-fed Conditionsmentioning

confidence: 99%

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Weibel

Garimella

2013

Advances in Heat Transfer

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Owing to their high reliability, simplicity of manufacture, passive operation, and effective heat transport, flat heat pipes and vapor chambers are used extensively in the thermal management of electronic devices. The need for concurrent size, weight, and performance improvements in high-performance electronics systems, without resort to active liquid-cooling strategies, demands passive heat spreading technologies that can dissipate extremely high heat fluxes from small hot spots. In response to these daunting application-driven trends, a number of recent investigations have focused on the design, characterization, and fabrication of ultra-thin vapor chambers for proximate heat spreading away from these hot spots. The predominant transport mechanisms and operational limits have been found to be different under these conditions relative to conventional low-power heat pipes. Noteworthy advances in the fundamental understanding of evaporation and boiling from porous microstructures fed by capillary action, and improvements in vapor chamber characterization, modeling, design, and fabrication techniques are reviewed. Characterization of evaporation and boiling from idealized and realistic wick structures, observation of vapor formation regimes as a function of operating conditions, assessment of fluid dryout limitations, design of novel multi-scale and nanostructured wicks for enhanced transport, and incorporation of these high heat flux transport phenomena into device-level models are discussed. These recent developments have successfully extended the maximum operating heat flux limits of vapor chambers.2

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Section: Incipience Of Boiling Under Capillary-fed Conditionsmentioning

confidence: 99%

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Weibel

Garimella

2013

Advances in Heat Transfer

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“…Following a similar analysis as proposed by Hsu [26], the superheated liquid layer thickness for FC-72 was estimated to be 100 µm (as in [25]); however, due to the high thermal conductivity of the current sintered copper coating as compared to the epoxy-based porous coating in [25], the observed optimum coating thickness was higher for the present coating (~400 µm). Figure 8 shows a direct comparison between the boiling curves obtained for the free-particle and sintered-coating enhancement techniques.…”

Section: Sintered Particle Coatingmentioning

confidence: 92%

“…The prediction of the optimum coating thickness was studied by Chang and You [25], and compared against experiments for boiling of FC-72 from surfaces coated with diamond particles. Based on an analysis that assumed a transient superheated liquid boundary layer to be formed above each nucleation site between successive bubble departures [26], an optimum coating thickness equal to the superheated liquid layer thickness was predicted. Using this optimum thickness as a threshold, coatings were categorized into micro-porous (below optimum) and porous (above optimum)…”

Section: Introductionmentioning

confidence: 99%

Effect of particle size on surface-coating enhancement of pool boiling heat transfer

Sarangi

Weibel

Garimella

2015

International Journal of Heat and Mass Transfer

126

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The enhancement of pool boiling heat transfer by copper-particle surface coatings is experimentally investigated, using the wetting dielectric fluid FC-72. In one technique, loose copper particles are placed on a heated copper surface to provide additional vapor nucleation sites in the cavities formed at particlesurface and particle-particle contact points, thereby enhancing boiling performance over a polished surface. This 'free-particle' technique is benchmarked against the more traditional technique of sintering a fixed layer of copper particles to the surface to enhance boiling heat transfer performance. The effect of particle size on the heat transfer performance is studied for particle diameters ranging from 45 µm to 1000 µm at a constant coating layer thickness-to-particle diameter ratio of approximately 4. The parametric trends in the boiling curve and the critical heat flux are compared between the two techniques, and the dominant boiling mechanisms influencing these trends are compared and contrasted. High-speed visualizations are performed to qualitatively assess the boiling patterns and bubble departure size/distribution, and thus corroborate the trends observed in the boiling curves. The measured wall superheat is significantly lower with a sintered coating compared to the free-particle layer for any given particle size and heat flux. Performance trends with respect to particle size, however, are remarkably similar for both enhancement techniques, and an optimum particle size of ~100 µm is identified for both free particles and sintered coatings. The free-particle technique is shown to offer a straightforward method to screen the boiling enhancement trends expected from different particulate layer compositions that are intended to be subsequently fabricated by sintering.

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“…Constant nucleating superheat corresponding to the given cavity diameter, D c , of the nucleate site [25] DT…”

Section: Numerical Modelmentioning

confidence: 99%

Influence of heater thermal capacity on bubble dynamics and heat transfer in nucleate pool boiling

Zhang

et al. 2015

Applied Thermal Engineering

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On the Size Range of Active Nucleation Cavities on a Heating Surface

Cited by 785 publications

References 0 publications

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Effect of particle size on surface-coating enhancement of pool boiling heat transfer

Influence of heater thermal capacity on bubble dynamics and heat transfer in nucleate pool boiling

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