Boiling on Coated Surfaces and in Porous Structures

Smirnov, Henry

doi:10.1615/jpormedia.v4.i1.40

Cited by 7 publications

(3 citation statements)

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“…2 inset). These observations are consistent with experiments 7,28 and models 2,29 characterizing the formation and growth of vapor bubbles within the porous structure and their subsequent escape comprising the boiling process in porous media. The maximum heat flux observed for the porous samples is consistent with a partial loss of cooling and, eventually, burnout due to the volumetric self-heating.…”

supporting

confidence: 90%

“…Conduction resistance in thin evaporating liquid films has been extensively analyzed and shown to be an important component of observed superheat, e.g., for individual menisci on heated surfaces 32 and boiling in porous layers. 29 We here present a brief order of magnitude estimate of this effect. We consider an effective liquid film thickness for the entire internal surface.…”

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confidence: 92%

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Approaching the limits of two-phase boiling heat transfer: High heat flux and low superheat

Palko

Zhang

Wilbur

et al. 2015

Applied Physics Letters

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We demonstrate capillary fed porous copper structures capable of dissipating over 1200 W cm À2 in boiling with water as the working fluid. Demonstrated superheats for this structure are dramatically lower than those previously reported at these high heat fluxes and are extremely insensitive to heat input. We show superheats of less than 10 K at maximum dissipation and varying less than 5 K over input heat flux ranges of 1000 W cm À2. Fabrication of the porous copper layers using electrodeposition around a sacrificial template allows fine control of both microstructure and bulk geometry, producing structures less than 40 lm thick with active region lateral dimensions of 2 mm Â 0.3 mm. The active region is volumetrically Joule heated by passing an electric current through the porous copper bulk material. We analyze the heat transfer performance of the structures and suggest a strong influence of pore size on superheat. We compare performance of the current structure to existing wick structures. V

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confidence: 90%

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confidence: 92%

Approaching the limits of two-phase boiling heat transfer: High heat flux and low superheat

Palko

Zhang

Wilbur

et al. 2015

Applied Physics Letters

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“…Smirnov [5] made heat transfer measurements in pool boiling conditions on multi-layered porous coated flat surfaces (both stainless steel layers and copper alloy layers). Within boiling conditions, he distinguished two different regions in terms of heat flux: a first "boiling" regime for relatively low heat fluxes where the heat transfer coefficient was quite high and varied less with heat flux, q −0.11 to −0.25 o , and a second "pool boiling" regime where the behavior was more similar to pool boiling on a plain surface.…”

Section: Pool Boilingmentioning

confidence: 99%

Falling Films on Arrays of Horizontal Tubes with R-134a, Part I: Boiling Heat Transfer Results for Four Types of Tubes

Roques

Thome

2007

Heat Transfer Engineering

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A new falling film heat transfer test facility has been built for the measurement of local heat transfer coefficients on a vertical array of horizontal tubes, including flow visualization capabilities, for use with refrigerants. Presently, the facility has been used for evaporation tests on four types of tubes at three tube pitches and three nominal heat flux levels for R-134a at 5 • C. A new method for determining local heat transfer coefficients using hot water heating has been applied, and test results for a wide range of liquid film Reynolds numbers have been measured for arrays made of plain, Turbo-BII HP, Gewa-B, and High-Flux tubes. The results show that there is a transition to partial dryout as the film Reynolds number is reduced, marked by a sharp falloff in heat transfer. Above this transition, the heat transfer coefficients are nearly insensitive to the filmReynolds number, apparently because vigorous nucleate boiling is always seen in the liquid film. The corresponding nucleate pool boiling data for the four types of tubes were also measured for direct comparison purposes. Overall, about 15,000 local heat transfer data points were obtained in this study as a function of heat flux, film Reynolds number, tube spacing, and type.

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