Superhydrophilic catenoidal aluminum micropost evaporator wicks

Bang, Soosik; Ryu, Seunggeol; Ki, Seokkan; Song, K. S.; Kim, Jin-Wook; Kim, Joongnyon; Nam, Youngsuk

doi:10.1016/j.ijheatmasstransfer.2020.120011

Cited by 20 publications

(13 citation statements)

References 57 publications

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“…The common adsorption of hydrophobic hydrocarbons from the ambient air onto metal surfaces often results in the quick degradation of their hydrophilic/capillary properties [21,116,117], making the creation of long-term stable wicking materials a challenging task. It is known that the treatment of aluminum in hot water improves its both hydrophilic/wicking properties and long-term stability [80][81][82][83]. These effects result from both the modification of the surface chemistry and the formation of "grass-like" surface nanostructures [82].…”

Section: Resultsmentioning

confidence: 99%

“…Our research on efficient wicking materials is motivated by a large variety of their applications in such areas as the thermal management of high-heat flux semiconductor electronics [65], cooling data centers [66,67], energy-harvesting [68], thermal management of robots [69], water desalination [18,70], waste heat recovery [71][72][73], spacecraft thermal management [74,75], and Maisotsenko cycle (M-cycle) technologies [76][77][78][79]. Our choice of aluminum is stimulated by its longterm stable wicking properties due to the formation of a hydrophilic aluminum oxide hydroxide [γ-AlO(OH)] surface layer (referred to as the Boehmite layer) caused by the chemical interaction of aluminum with hot water that improves both the hydrophilic and corrosion-resistance properties of Al wicks [80][81][82][83]. Previously, capillary flow dynamics in microgrooves produced on an aluminum surface by femtosecond laser pulses has been studied at the stage of the classic Washburn flow at room temperature [15,16,18].…”

Section: Introductionmentioning

confidence: 99%

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Superwicking Functionality of Femtosecond Laser Textured Aluminum at High Temperatures

et al. 2021

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An advanced superwicking aluminum material based on a microgroove surface structure textured with both laser-induced periodic surface structures and fine microholes was produced by direct femtosecond laser nano/microstructuring technology. The created material demonstrates excellent wicking performance in a temperature range of 23 to 120 °C. The experiments on wicking dynamics show a record-high velocity of water spreading that achieves about 450 mm/s at 23 °C and 320 mm/s at 120 °C when the spreading water undergoes intensive boiling. The lifetime of classic Washburn capillary flow dynamics shortens as the temperature increases up to 80 °C. The effects of evaporation and boiling on water spreading become significant above 80 °C, resulting in vanishing of Washburn’s dynamics. Both the inertial and visco-inertial flow regimes are insignificantly affected by evaporation at temperatures below the boiling point of water. The boiling effect on the inertial regime is small at 120 °C; however, its effect on the visco-inertial regime is essential. The created material with effective wicking performance under water boiling conditions can find applications in Maisotsenko cycle (M-cycle) high-temperature heat/mass exchangers for enhancing power generation efficiency that is an important factor in reducing CO2 emissions and mitigation of the global climate change.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Superwicking Functionality of Femtosecond Laser Textured Aluminum at High Temperatures

et al. 2021

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“…Such wicks consist of an array of micropillars, and their performance has been investigated both experimentally and numerically for thin-film evaporation applications. Some of the well-defined micropillar geometries that have been explored in the past for evaporative cooling are as follows: (a) cylindrical: ,,− one of the most common and optimized micropillar geometry due to their ease of fabrication, provides better thermal performance at low to mid heat flux conditions; (b) pyramidal: provides high capillary pumping at lower contact angles and better thin-film area available for evaporation; (c) conical: low dryout heat flux and effective heat transfer coefficient compared to cylinders due to less curvature of meniscus; (d) pies: shows marginal enhancement of effective heat transfer coefficient as a result of increase in thin-film region; (e) rectangular ribs: , maximum capillary pressure generated is lower than cylinder but has comparable thin-film area fraction; (f) mushroom-shaped: provides lower overall thermal resistance as result of thinner thin-film region; (g) catenoidal: re-pinning of meniscus led to higher maximum effective heat transfer coefficient than cylinder but has comparable capillary performance; (h) gradient cuboid: generates high capillary pumping pressure and at the same time has better effective heat flux throughout the meniscus than cuboidal micropillar. Additionally, wicks with nonuniform micropillar distribution and segmented arrangement of micropillars have also been reported to simultaneously maximize dryout heat flux and minimize thermal resistance.…”

Section: Introductionmentioning

confidence: 99%

“…(g) catenoidal: 20 re-pinning of meniscus led to higher maximum effective heat transfer coefficient than cylinder but has comparable capillary performance; (h) gradient cuboid: 21 generates high capillary pumping pressure and at the same time has better effective heat flux throughout the meniscus than cuboidal micropillar. Additionally, wicks with nonuniform micropillar distribution 22 and segmented arrangement 7 of micropillars have also been reported to simultaneously maximize dryout heat flux and minimize thermal resistance.…”

Section: ■ Introductionmentioning

confidence: 99%

Biomimetic Micropillar Wick for Enhanced Thin-Film Evaporation

Sharma

2023

Langmuir

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Sustainable liquid cooling solutions are recognized as the future of thermal management in the chip industry. Among them, phase change heat transfer devices such as heat pipes and vapor chambers have shown tremendous potential. These devices rely on the physics of capillary-driven thin-film evaporation, which is inherently coupled with the design and optimization of the evaporator wicks used in these devices. Here, we introduce a biomimetic evaporator wick design inspired by the peristome of the Nepenthes alata that can achieve significantly enhanced evaporative cooling. It consists of an array of micropillars with multiple wedges along the sidewall of each micropillar. The efficacy of the wedged micropillar is evaluated based on a validated numerical model on the metrics of dryout heat flux and effective heat transfer coefficient. The wedge angle is chosen such that wedged micropillars cause liquid filaments to rise along the micropillar vertical walls. This results in a significant increase in thin-film area for evaporation. Additionally, the large mean curvature of the liquid meniscus produces strong capillary pumping pressure and simultaneously, the wedges increase the overall permeability of the wick. Consequently, our model predicts that the wedged micropillar wick can attain ∼234% enhancement of dryout heat flux compared to a conventional cylindrical micropillar wick of similar geometrical dimensions. Moreover, the wedged micropillars can also attain a higher effective heat transfer coefficient under dryout conditions, thus outperforming the cylindrical micropillar in terms of heat transfer efficiency. Our study provides insight into the design and capability of the biomimetic wedged micropillars as an efficient evaporator wick for various thin-film evaporation applications.

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“…Hu et al 12 fabricated 3D printed wicks of stainless steel by means of the 3D printing technique, to evade high unpredictability and presence of sealed pores in the conventional sintered wicks for a flat LHP. The outcomes show that the least evaporator thermal resistance is 0.031 K/W at a heat load of 140 W. Bang et al 13 fabricated super hydrophilic catenoidal aluminium wicks by means of multistep wet etching method trailed by means of wet chemical oxidation and incorporated nanostructured aluminium oxide layer to augment the corrosion resistance in addition to the wettability of wick with water. Outcomes show that the heat transfer coefficient of established wick promptly increases as the heat flux rises up to ~60 W/cm 2 .…”

Section: Introductionmentioning

confidence: 99%

Effect of low thermal conductivity wick on the performance of compact loop heat pipe

Veeramachaneni¹,

Pisipaty

Solomon

et al. 2022

Heat Trans

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The existing work deals with the evaluation of compact loop heat pipe by means of a low thermal conductivity sintered chrysotile wick to avoid large heat leaks as of the evaporator to the compensation chamber. Accordingly, a wick with low thermal conductivity (0.068–0.098 W/mK) chrysotile powder of a mean particle diameter of 3.4 μm is fabricated through sintering. Nine chrysotile wicks are sintered with different compositions of binders (bentonite and dextrin) and pore‐forming agent NaCl at sintering temperatures of 500°C, 600°C, and 700°C with a sintering time of 30 min. The wick properties, for instance, porosity, permeability, wettability, and capillary rise are studied owing to sintering temperature. Consequently, it is observed that a pure chrysotile powdered wick at a sintering temperature of 600°C exhibits a high porosity of 61.8% with permeability 1.04 × 10−13 m2 and a capillary rise of 4.5 cm in 30 s and is considered optimal. This optimal wick is used for performance evaluation in compact loop heat pipe and a decrease of 36.1% in thermal resistance is found when compared with copper mesh wick in a loop heat pipe. The lowermost thermal resistance originates to be 0.147 K/W at 120 W with wall temperature 57.7°C. This indicates that loop heat pipe with sintered chrysotile wick can operate at lower heat loads efficiently when compared with copper mesh wick and as heat load increases a chance of dry out condition occurs. The highest evaporative heat transfer coefficient obtained is 65.7 kW/m2 K at a minimum heat load.

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Superhydrophilic catenoidal aluminum micropost evaporator wicks

Cited by 20 publications

References 57 publications

Superwicking Functionality of Femtosecond Laser Textured Aluminum at High Temperatures

Superwicking Functionality of Femtosecond Laser Textured Aluminum at High Temperatures

Biomimetic Micropillar Wick for Enhanced Thin-Film Evaporation

Effect of low thermal conductivity wick on the performance of compact loop heat pipe

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