Photonically enhanced flow boiling in a channel coated with carbon nanotubes

Kousalya, Arun S.; Hunter, Chad N.; Putnam, Shawn A.; Miller, Timothy J.; Fisher, Timothy S.

doi:10.1063/1.3681594

Cited by 33 publications

(7 citation statements)

References 23 publications

(30 reference statements)

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“…Similar results were obtained by Singh et al [65] with CNTs on silicon substrates. Recently, Kousalya et al [66] employed ultraviolet light on the CNT structures and reported an improvement in heat transfer performance with a 4.6 C reduction in the wall superheat at a heat flux of around 50 W/cm 2 . The ultraviolet light was utilized to make a CNT surface hydrophilic as originally reported by Takata et al [67].…”

Section: Nanostructuresmentioning

confidence: 99%

Heat Transfer in Microchannels—2012 Status and Research Needs

Kandlikar

Colin

Peles

et al. 2013

Journal of Heat Transfer

231

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Heat transfer and fluid flow in microchannels have been topics of intense research in the past decade. A critical review of the current state of research is presented with a focus on the future research needs. After providing a brief introduction, the paper addresses six topics related to transport phenomena in microchannels: single-phase gas flow, enhancement in single-phase liquid flow and flow boiling, flow boiling instability, condensation, electronics cooling, and microscale heat exchangers. After reviewing the current status, future research directions are suggested. Concerning gas phase convective heat transfer in microchannels, the antagonist role played by the slip velocity and the temperature jump that appear at the wall are now clearly understood and quantified. It has also been demonstrated that the shear work due to the slipping fluid increases the effect of viscous heating on heat transfer. On the other hand, very few experiments support the theoretical models and a significant effort should be made in this direction, especially for measurement of temperature fields within the gas in microchannels, implementing promising recent techniques such as molecular tagging thermometry (MTT). The single-phase liquid flow in microchannels has been established to behave similar to the macroscale flows. The current need is in the area of further enhancing the performance. Progress on implementation of flow boiling in microchannels is facing challenges due to its lower heat transfer coefficients and critical heat flux (CHF) limits. An immediate need for breakthrough research related to these two areas is identified. Discussion about passive and active methods to suppress flow boiling instabilities is presented. Future research focus on instability research is suggested on developing active closed loop feedback control methods, extending current models to better predict and enable superior control of flow instabilities. Innovative high-speed visualization and measurement techniques have led to microchannel condensation now being studied as a unique process with its own governing influences. Further work is required to develop widely applicable flow regime maps that can address many fluid types and geometries. With this, condensation heat transfer models can progress from primarily annular flow based models with some adjustments using dimensionless parameters to those that can directly account for transport in intermittent and other flows, and the varying influences of tube shape, surface tension and fluid property differences over much larger ranges than currently possible. Electronics cooling continues to be the main driver for improving thermal transport processes in microchannels, while efforts are warranted to develop high performance heat exchangers with microscale passages. Specific areas related to enhancement, novel configurations, nanostructures and practical implementation are expected to be the research focus in the coming years.

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Section: Nanostructuresmentioning

confidence: 99%

Heat Transfer in Microchannels—2012 Status and Research Needs

Kandlikar

Colin

Peles

et al. 2013

Journal of Heat Transfer

231

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show abstract

“…Further, while the hydrophilicity of NWs and CNTs with water has been reported in the literature [205,206], aligned arrays of nanotubes have also been shown to behave as superhydrophobic surfaces [207]. Hence, surfactants may be used for liquid conveying applications [208], or nanostructures may be functionalized for heat transfer applications via metallization [51], hydrochloric acid treatment [209], or ultraviolet excitation [210]. Nanostructures have a high number of pores per unit substrate area, and thereby may also offer an increase in the thin-film area for evaporation.…”

Section: Nanostructured Capillary Wicks For Vapor Chamber Applicationsmentioning

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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“…Artificial nucleation cavities were formed on the boiling surfaces to enhance nucleate boiling by various methods, such as micromachining [18][19][20][21], nanostructured surfaces [22][23][24][25][26], porous metal coating [27][28][29], and chemical etching [30,31]. Recently, nanowires (NWs) [32,33] and carbon nanotubes (CNTs) [34][35][36] were used to enhance nucleate pool boiling and convective boiling in microchannels [23,25,26,34,37,38] coefficient and critical heat flux were reported owing to the higher nucleation site density and enhanced wettability. However, optimization of surface properties to control bubble size, forces acting on bubble and flow patterns/ regimes has not yet been well resolved.…”

Section: Introductionmentioning

confidence: 99%

Force analysis and bubble dynamics during flow boiling in silicon nanowire microchannels

Alam

Yang

et al. 2016

International Journal of Heat and Mass Transfer

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a b s t r a c tIn microchannel flow boiling, bubble nucleation, growth and flow regime development are highly influenced by channel cross-section and physical phenomena underlying this flow boiling mechanism are far from being well-established. Relative effects of different forces acting on wall-liquid and liquid-vapor interface of a confined bubble play an important role in heat transfer performances. Therefore, fundamental investigations are necessary to develop enhanced microchannel heat transfer surfaces. Force analysis of nucleating bubble and bubble dynamics in flow boiling silicon nanowire microchannels have been performed based on theoretical, experimental and visualization studies. The relative effects of different forces on flow regimes, instabilities and heat transfer performances of flow boiling in silicon nanowire microchannels have been identified. Inertia, surface tension, shear, buoyancy, and evaporation momentum forces have significant importance at liquid-vapor interface as discussed earlier by other researchers. However, no comparative study has been done for different surface properties till date. Detail analyses of these forces including contact angle effect, channel dimension effect, heat flux effect and mass flux effect in flow boiling microchannels have been conducted in this study. A comparative study between silicon nanowire and plainwall microchannels has been performed based on force analysis in the flow boiling microchannels. Compared to plainwall microchannels, enhanced surface rewetting and CHF are owing to higher surface tension force at liquid-vapor interface and Capillary dominance resulting from silicon nanowires. Whereas, low Weber number in silicon nanowire helps maintaining uniform and stable thin film and improves heat transfer performances. Moreover, results from these studies are compared with the literatures and great agreements have been observed.

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Photonically enhanced flow boiling in a channel coated with carbon nanotubes

Cited by 33 publications

References 23 publications

Heat Transfer in Microchannels—2012 Status and Research Needs

Heat Transfer in Microchannels—2012 Status and Research Needs

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

Force analysis and bubble dynamics during flow boiling in silicon nanowire microchannels

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