Pool-boiling enhancement using multilevel modulated wick

Nasersharifi, Yahya; Kaviany, Massoud; Hwang, Gisuk

doi:10.1016/j.applthermaleng.2018.03.073

Cited by 59 publications

(17 citation statements)

References 67 publications

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“…Maximum enhancement in CHF of coated surfaces was reported 3.3 and 2.0 times higher as compared to plain surfaces. To control the vapor and liquid flow for efficient phase separation, Nasersharifi et al [152] developed and tested several multilevel modulated wicks such as columnar, monolayer and mushroom posts wicks as shown in Figure 13. The surface was fabricated using 200 µm copper particles by multi-step sintering process.…”

Section: Micro-scale Coatingsmentioning

confidence: 99%

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Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review

2018

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Nucleate boiling is a phase change heat transfer process with a wide range of applications i.e., steam power plants, thermal desalination, heat pipes, domestic heating and cooling, refrigeration and air-conditioning, electronic cooling, cooling of turbo-machinery, waste heat recovery and much more. Due to its quite broad range of applications, any improvement in this area leads to significant economic, environmental and energy efficiency outcomes. This paper presents a comprehensive review and critical analysis on the recent developments in the area of micro-nano scale coating technologies, materials, and their applications for modification of surface geometry and chemistry, which play an important role in the enhancement of nucleate boiling heat transfer. In many industrial applications boiling is a surface phenomenon, which depends upon its variables such as surface area, thermal conductivity, wettability, porosity, and roughness. Compared to subtractive methods, the surface coating is more versatile in material selection, simple, quick, robust in implementation and is quite functional to apply to already installed systems. The present status of these techniques for boiling heat transfer enhancement, along with their future challenges, enhancement potentials, limitations, and their possible industrial implementation are also discussed in this paper.

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Section: Micro-scale Coatingsmentioning

confidence: 99%

“…Schematic of multi-level modulated wicks with liquid/vapor flow, wick geometries and hydrodynamic instability wavelengths studied by[152]: (Design A) plain surface; (Design B) monolayer; (Design C) columnar posts; (Design D) mushroom posts wicks[152].…”

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confidence: 99%

Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review

2018

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“…A systematic study was carried out for the nucleation site densities at a high-pressure pool-boiling experiment and reported that the nucleation site density increases in proportion of 1.5th of the pressure. Many surface modification methods have been employed to enhance the performance of the pool-boiling heat transfer and understand CHF enhancement mechanism including surface roughness (Jones et al, 2009), micro/nanostructured surfaces (Jo et al, 2012), wettability (Takata et al, 2003(Takata et al, , 2006Nam and Ju, 2008;Betz et al, 2010Betz et al, , 2011Betz et al, , 2013Jo et al, 2016;Marcel et al, 2017), addition of nanoparticles (Trisaksri and Wongwises, 2009), extended surfaces like microchannels (Jaikumar and Kandlikar, 2015a,b), porous coatings (Hwang and Kaviany, 2006), and modulated wick surface (Nasersharifi et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

High-Pressure Pool-Boiling Heat Transfer Enhancement Mechanism on Sintered-Particle Wick Surface

et al. 2020

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We experimentally study high-pressure pool-boiling heat transfer enhancement using a copper sintered-particle wick structure in water. The wicks are fabricated using the multi-step sintering process using 200 µm sintered copper powder. Thermophysical properties of water change at elevated pressure, therefore changing the bubble dynamics. For the single-layer wick, Critical Heat Fluxes (CHF) of 179.63, 182.42, and 198.16 W/cm 2 are found at 0, 103.4, and 206.8 kPa, respectively. The maximum CHF is found at 206.8 kPa with the wick superheat of 9.9 K. A 110% enhancement is found in the CHF for 206.8 kPa, compared to 0 kPa. We observed a CHF 1.8 times higher compared to the plain surface at 0 kPa. The maximum Heat Transfer Coefficient (HTC) of 252.46 W/cm 2 K is found at a heat flux of 100 W/cm 2 and a pressure of 206.8 kPa. The high-pressure pool-boiling result for the single-layer wick shows that the heat transfer coefficient is enhanced by 100% compared to 0 kPa. We suggest the reasons for enhancement of the pool-boiling performance is primarily due to high rate of bubble generation, high bubble release frequency, and reduced thermal-hydraulic length modulation, and enhanced thermal conductivity due to the sintered wick layer. Our analysis suggests that the Rayleigh-critical wavelength decreases by 4.67% with varying pressure, which may cause the bubble pinning between the sintered particles and prevents bubble coalescence. Similarly, the role of pressure in enhancing heat transfer compared to the effect of the wicking layer is also analyzed and found that the critical flow length, λ u reduces by three times for 200 µm diameter particles. We suggest that the porous wick layer provides a capillary-assist to liquid flow effect, and delays the surface dry out. The pressure and surface modification amplify the boiling heat transfer performance. All these reasons may contribute to the CHF and HTC enhancement in the wicking layer at high-pressure.

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“…These designs make use of dedicated feeding structures to enhance liquid supply while also providing vapor removal pathways. In pool boiling, recent studies have used porous wicks made from modulated post designs [14] or containing re-entrant cavities [15] to enhance the heat transfer coefficient and improve the critical heat flux (CHF). For enhanced capillary-fed boiling in evaporator wicks, heterogeneous wick designs aim to provide simultaneous high capillary pressure and high permeability, as an alternative to thick biporous wicks.…”

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confidence: 99%

“…to form these post-array wick structures, for which removal of the sintered sample is difficult and requires special design considerations (e.g., see Ref [14]…”

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confidence: 99%

Experimental investigation of boiling regimes in a capillary-fed two-layer evaporator wick

Sudhakar

Weibel

Garimella

2019

International Journal of Heat and Mass Transfer

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Vapor chambers with transformative evaporator wick designs capable of passively dissipating high heat fluxes over large areas, while maintaining low thermal resistances, can meet the thermal management needs of next-generation power semiconductor devices. Our prior work proposed a two-layer evaporator wick structure to enhance the performance of vapor chambers operating at high heat fluxes. The current study experimentally characterizes the capillary-fed boiling heat transfer behavior in such a two-layer evaporator wick, compared to a homogeneous (single-layer) wick, over a 1 cm 2 evaporator area. The two-layer design comprises a thin base wick layer that is fed with liquid from a thick cap wick layer above using an array of vertical posts. The two-layer wick is fabricated using a sequence of sintering and laser-machining steps to form the base wick layer (200 µm), array of liquid-feeding posts, and cap wick layer (800 µm) using 90-106 µm copper particles. A test facility is constructed to replicate the conditions that exist at the evaporator of a vapor chamber; the novel facility design uses a physical restriction to prevent flooding of the wicks during testing. Two-layer wicks having 5×5 and 10×10 arrays of liquid feeding posts are characterized, along with a 200 µm-thick single-layer evaporator wick. The 10×10 array provides a >400% enhancement in the dryout heat flux compared to the single-layer wick. High-speed visualizations are used to identify the characteristic regimes of boiling operations for the wicks. The single-layer wick exhibits a partial dryout mode of operation, where a dry spot formed in the center of the heated evaporator area causes an increase in the thermal resistance with heat flux. In contrast, the distributed feeding provided by the two-layer wicks mitigates the development of this partial dryout regime and maintains a constant low resistance (~ 0.1 K/W) during capillary-fed boiling until a complete dryout event occurs. This study demonstrates the significant enhancement in dryout heat flux offered by the liquid-feeding approach realized in the two-layer evaporator wicks characterized here.

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Pool-boiling enhancement using multilevel modulated wick

Cited by 59 publications

References 67 publications

Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review

Micro-Nano Scale Surface Coating for Nucleate Boiling Heat Transfer: A Critical Review

High-Pressure Pool-Boiling Heat Transfer Enhancement Mechanism on Sintered-Particle Wick Surface

Experimental investigation of boiling regimes in a capillary-fed two-layer evaporator wick

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