Nanowires for Enhanced Boiling Heat Transfer

Chen, Renkun; Lu, Ming; Srinivasan, Vinod; Wang, Zhijie; Cho, Hyung Hee; Majumdar, Arun

doi:10.1021/nl8026857

Cited by 593 publications

(429 citation statements)

References 28 publications

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“…A similar analysis has been employed by others with satisfactory predictions [17,34]. Using a volumetric porosity ε of 0.5±0.02, an average breakthrough bubble diameter d br of 42 μm (determined from the average pore diameter ), and thermophysical properties of water at saturation temperature (100 °C), the hydrodynamic limit of the bare sample is estimated to be 906±102 W/cm 2 using: …”

Section: Mechanism Of Dryoutmentioning

confidence: 91%

“…Liter and Kaviany [34] demonstrated that the hydrodynamic limit can be significantly increased using modulated porous structures which provide preferential flow paths for liquid and vapor, thereby reducing the liquid/vapor counterflow situations and aiding non-hydrodynamical determination of the critical instability wavelength. Various other studies also report a significant increase in critical heat flux (CHF) of uniformly coated porous surfaces compared to plain surfaces investigated under natural convection boiling conditions [17,35]. Reasons for this reported enhancement include heat transfer from extended surfaces, an increase in nucleation site density, and enhanced lateral liquid replenishment to the active nucleation sites via capillary action that reduces the liquid-vapor counterflow resistance.…”

Section: Mechanism Of Dryoutmentioning

confidence: 96%

“…Nanostructured coatings provide pore radii on the order of a few tens of nanometer, at least two orders of magnitude less than the few tens of micron pore sizes prevalent in traditional porous surfaces, and hence provide high capillary pressures to overcome the viscous drag on fluid flow at the microscale and delay capillary dryout. Chen et al [17] reported Complete coverage and patterning of wick surfaces with carbon nanotubes (CNTs) has found considerable interest in the research community [14,15,21]. CNTs are cylindrical nanostructures of graphitic carbon with outer diameters ranging from 1 to 100 nm and typical lengths from 1 to 50 μm.…”

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: Mechanism Of Dryoutmentioning

confidence: 91%

Section: Mechanism Of Dryoutmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…Solid-liquid-vapor interfaces controlled by the TCL exist widely in multiphase interfaces systems, which is important in biological [36] and industrial processes. [37] Numerous papers report static state [38] and dynamic state [9d,39] aspects of the exterior TCL on textured surfaces. However, a few quantitative methods for the direct nanoscale visualization of the 3D droplet and underlying substrate interface result from the low resolution of measurement techniques.…”

Section: Scanning Electron Microscopymentioning

confidence: 99%

Direct Imaging of Superwetting Behavior on Solid–Liquid–Vapor Triphase Interfaces

Peng

Zheng

et al. 2017

Advanced Materials

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has been established. The contact angle is the first parameter to directly and quantitatively characterize the wetting behavior of a surface. The apparent contact angle is mainly determined by the thermodynamic equilibrium among three coexisting phases: the solid phase, the liquid phase, and the vapor phase (Figure 1a), meanwhile influenced by the scale ratio between the measured liquid droplet and the hierarchical structure. In the ideal scenarios when the solid surface has a perfectly planar geometry and is chemically homogeneous (Figure 1a), the contact angle can be obtained via the well-known Young's equation. [1] However, in practical circumstances, the solid surface possesses different degrees of roughness, which deviates from the basic assumption of Young's equation. In 1936, Wenzel [2] proposed a typical wetting model for a solid with a rough surface. In Wenzel's model, the liquid completely infiltrates the microscale/nanoscale structure of the rough surface (Figure 1b), which successfully explained the contribution of surface roughness to surface wetting behavior. In addition, the Cassie model [3] is another typical wetting model, which was presented in 1944 by Cassie and Baxter. Their results indicated that the presence of air pockets between the liquids and the substrate can significantly affect the special wettability of surfaces (as shown in Figure 1c). Therefore, two typical models of wetting behaviors are applied to correlate the relationship between apparent contact angle and surface roughness. [4] The wettability of solid surfaces is dominated mainly by both chemical composition and geometric structures of the solid surface, as many experiments with multifunctional materials via bioinspired strategies have proven. As a result, studying multiphase wetting behavior is beneficial for developing wetting theory and providing guidance on the precise structure of pioneering materials. That is, the multiphase wetting behaviors of solid surfaces contain solid-liquid-vapor triphase interfaces, which are dominated by the three-phase contact line (TCL). Research on the TCL of solid-liquid-vapor interfaces includes not only fundamental investigations but also a broad domain of promising practical applications in the field of advanced materials, medical science, biotechnology, and electronic devices. [5] In the past few decades, the crystallization process dominated by the surface wettability has been confirmed, and the strategy for controlling surface wetting is a critical step to the fabrication of single-crystal arrays in the whole crystallization process. [6] Recently, Song and co-workers reported a promising method to A solid-liquid-vapor interface dominated by a three-phase contact line usually serves as an active area for interfacial reactions and provides a vital clue to surface behavior. Recently, direct imaging of the triphase interface of superwetting interfaces on the microscale/nanoscale has attracted broad scientific attention for both theoretical research and practical applications, and has ...

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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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Nanowires for Enhanced Boiling Heat Transfer

Cited by 593 publications

References 28 publications

Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

Metal functionalization of carbon nanotubes for enhanced sintered powder wicks

Direct Imaging of Superwetting Behavior on Solid–Liquid–Vapor Triphase Interfaces

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

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