Effects of carbon nanotube arrays on nucleate pool boiling

Ujereh, Sebastine O.; Fisher, Timothy S.; Mudawar, Issam

doi:10.1016/j.ijheatmasstransfer.2007.01.030

Cited by 248 publications

(129 citation statements)

References 19 publications

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“…Comparison of thermal resistances of the four samples (Fig. 8) The propensity of CNTs to initiate bubble nucleation at lower surface superheats was previously reported in pool boiling studies [22,24] as well as for CNT-enhanced wicks [16,26]. It is notable that this phenomenon is independent of wick thickness for millimeter and sub-millimeter thick wicks.…”

Section: Effect Of Varying Cnt Copper Coating Thickness On Overall Thsupporting

confidence: 59%

“…Ujereh et al [22] performed pool boiling experiments on CNTcoated silicon and copper substrates with distinct patterned areas of coverage and differing CNT array densities. Surfaces coated entirely with CNTs eliminated the large incipience superheat overshoot and the resulting substantial temperature drop upon incipience observed in the case of bare silicon and copper surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

Kousalya

Weibel

Garimella

et al. 2013

International Journal of Heat and Mass Transfer

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Phase change cooling schemes involving passive heat spreading devices, such as heat pipes and vapor chambers, are widely adopted for thermal management of high heat-flux technologies. In this study, carbon nanotubes (CNTs) are fabricated on a 200 μm thick sintered copper powder wick layer using a microwave plasma enhanced chemical vapor deposition technique. A physical vapor deposition process is used to coat the CNTs with a varying thickness of copper to promote surface wetting with the working fluid, water. Thermal performance of the bare sintered copper powder sample (without CNTs) and the copper-functionalized CNT-coated sintered copper powder wick samples is compared using an experimental facility that simulates the capillary fluid feeding conditions of a vapor chamber. A notable reduction in the boiling incipience superheat is observed for the nanostructured samples. Additionally, nanostructured samples having a thicker copper coating provided a considerable increase in dryout heat flux, supporting heat fluxes up to 457 W/cm 2 from a 5 mm × 5 mm heat input area, while maintaining lower surface superheat temperatures compared to a bare sintered powder sample; this enhancement is attributed primarily to the improved surface wettability. Dynamic contact angle measurements are conducted to quantitatively compare the surface wetting trends for varying copper coating thicknesses and confirm the increase in hydrophilicity with increasing coating thickness.

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Section: Effect Of Varying Cnt Copper Coating Thickness On Overall Thsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

Kousalya

Weibel

Garimella

et al. 2013

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

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“…Nanostructures have been reported to improve differing aspects of the boiling process (e.g., incipience, nucleation boiling, and critical heat flux) via CNT-coating of silicon [211][212][213] and copper substrates [80,213], and copper nanowire [214][215][216] and silicon nanowire [215][216][217] surface coatings.…”

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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“…29 The second theoretical group describing the onset of CHF covers the ability of the surface to resupply hotspots with cool liquid, 30 and has been referenced in many of the latest research efforts on nanoscale surface structures. 18,22,31,32 The hydrodynamic instability theory states that CHF will be reached once hydrodynamic instability of vapor columns occurs. The model recognizes the vapor streams leaving the surface create separate channels of liquid and vapor.…”

Section: Resultsmentioning

confidence: 99%

A systematic study of pool boiling heat transfer on structured porous surfaces: From nanoscale through microscale to macroscale

Rioux

Nolan

2014

AIP Advances

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An experimental study has been conducted to examine the effects of macroscale, microscale, and nanoscale surface modifications in water pool boiling heat transfer and to determine the different heat transfer enhancing mechanisms at different scales. Nanostructured surfaces are created by acid etching, while microscale and macroscale structured surfaces are synthesized through a sintering process. Six structures are studied as individual and collectively integrated surfaces from nanoscale through microscale to macroscale: polished plain, flat nanostructured, flat porous, modulated porous, nanostructured flat porous, and nanostructured modulated porous. Boiling performance is measured in terms of critical heat flux (CHF) and heat transfer coefficient (HTC). Both HTC and CHF have been greatly improved on all modified surfaces compared to the polished baseline. Hierarchical multiscale surfaces of integrated nanoscale, microscale, and macroscale structures have been proven to have the most significant improvements on HTC and CHF. The CHF and HTC of the hierarchical multiscale modulated porous surface have achieved the most significant improvements of 350% and 200% over the polished plain surface, respectively. Experimental results are compared to the predictions of a variety of theoretical models with an attempt to reveal the different heat transfer enhancing mechanisms at different scales. It is concluded that models for the structured surfaces at all scales need to be further developed to be able to have good quantitative predictions of CHFs on structured surfaces.

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Effects of carbon nanotube arrays on nucleate pool boiling

Cited by 248 publications

References 19 publications

Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

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

A systematic study of pool boiling heat transfer on structured porous surfaces: From nanoscale through microscale to macroscale

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