Can multiple flow boiling regimes be reduced into a single one in microchannels?

Yang, Fanghao; Dai, Xianming; Peles, Yoav; Cheng, Ping; Li, Chen

doi:10.1063/1.4816594

Cited by 40 publications

(22 citation statements)

References 38 publications

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“…At the highest mass flux of 2206 kg/m 2 •s, it is noticeable that CHF in nanostructured microchannels was even reduced compared to that in plain-wall microchannels. This result is radically different from the results on DI water, which shows that CHFs increase with mass fluxes and have been significantly enhanced under all operating conditions conducted in experiment [18]. As shown in in Fig.…”

Section: Critical Heat Fluxcontrasting

confidence: 83%

“…The transformation of the capillary pressure from the cross-sectional planes into in-wall planes (Fig. 4a) leads to suppress the dominance of bubbly and slug flows and more importantly, creates a capillarity-induced annular flow at low mass flux and vapor quality, which is consistent with the flow pattern observed on deionized (DI) water in our previous study [18]. Periodical capillary flow was established on the inner walls as illustrated in Fig.…”

Section: Two-phase Flow Patternssupporting

confidence: 77%

“…Compared to flow boiling on DI water on similar structures [18], this study shows that it is more difficult to generate capillarity-induced annular flow for lower-surface-tension dielectric fluids, such as HFE-7000, particularly at high mass flux. When the mass flux and vapor quality increase to some extent (e.g.…”

Section: Page 22 Of 28mentioning

confidence: 95%

“…These existing studies suggest that NWs could potentially improve flow boiling heat transfer of dielectric fluids in microchannels. Furthermore, it has been demonstrated that NWs can regulate flow patterns to promote highly efficient thin film evaporation and hence play an Page 4 of 28 5 important role in substantially enhancing the overall heat transfer rate of flow boiling in microchannels on water in our previous studies [15][16][17][18]. However, previous studies to understand the interactions between nanostructures on dielectric fluids in parallel microchannels are still limited.…”

Section: Introductionmentioning

confidence: 97%

“…Engineered by advanced nanofabrication techniques [18,19], all inner surfaces of silicon microchannels were integrated with Si nanowires to form micro/nanoscale porous structures ( Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels

Yang

Dai

et al. 2016

Applied Thermal Engineering

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Please cite this article as: Fanghao Yang, Wenming Li, Xianming Dai, Chen Li, Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels, Applied Thermal Engineering (2015), http://dx.doi.org/ABSTRACT: Flow boiling of dielectric fluids in microchannels is among the most promising embedded cooling solutions for high power electronics. However, it is normally limited by their poor thermal conductivity and small latent heat. To promote thin film evaporation and nucleate boiling, the side and bottom walls of five parallel microchannels were structured with nanowires in a silicon chip. A 10-mm-long thin-film heater were built-in to simulate heat source. Wall Page 1 of 28 2 temperatures were measured from adiabatic condition to critical heat flux (CHF) conditions. Compared to the plain-wall microchannels with identical channel dimensions, heat transfer coefficient of HFE 7000 can be substantially enhanced up to 344% at the mass flux ranging from 1018 kg/m 2 •s to 2206 kg/m 2 •s as promoted evaporation and nucleate boiling. Moreover, pumping power was reduced up to 40% owing to the capillarity-enhanced phase separation. CHF was achieved from 92 to 120 W/cm 2 and enhanced up to 14.9% at moderate mass flux of 1018 kg/m 2 •s as a result of annular liquid supply. However, interestingly, this trend is non-monotonic and CHF is reduced at higher mass fluxes. This experimental study is trying to explore an optimal range of working conditions using nanostructures in flow boiling on highly-wetting dielectric fluids. NomenclatureA Area, m 2 D Diameter, m H Height, m h fg Latent heat of vaporization, kJ/kg G Mass flux, kg/m 2 •s L Length, m m

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Section: Critical Heat Fluxcontrasting

confidence: 83%

Section: Two-phase Flow Patternssupporting

confidence: 77%

Section: Page 22 Of 28mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Flow boiling heat transfer of HFE-7000 in nanowire-coated microchannels

Yang

Dai

et al. 2016

Applied Thermal Engineering

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Endoscopic Visualization of Contact Line Dynamics during Pool Boiling on Capillary‐Activated Copper Microchannels

Zhu²,

Kang

et al. 2020

Adv Funct Materials

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Microchannel surfaces are common to microfluidics, biofluidics, thermal management, and energy applications. Due to processing limitations for the majority of metallic materials, the majority of hyperfine microchannels used in microfluidics and thermo‐fluids are fabricated on non‐metallic substrates, for example, silicon and polydimethylsiloxane. Here, a technique to fabricate ultrasmall microchannels on arbitrary metallic materials is developed using photolithography in combination with electrochemical deposition. The technique is used to prepare copper microchannels and to investigate the pool boiling heat transfer performance with a focus on the three‐phase contact line dynamics. The hydrodynamics of nucleating bubbles during boiling are observed in situ using in‐liquid endoscopy. The results show that the variation of critical heat flux enhancement has a linear relationship with the contact line increase ratio. The scalable microchannel surfaces exhibit superior heat transfer performance with a maximum heat transfer coefficient) enhancement of 930% with ultra‐low wall superheat of 5 °C. This work not only develops a scalable manufacturing method to develop ultra‐small microchannels on metallic materials, it outlines design guidelines for structure optimization of pool boiling heat transfer for temperature sensitive applications, such as electronics thermal management.

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