Modifying capillary pressure and boiling regime of micro-porous wicks textured with graphene oxide

Jo, Hong Seok; An, Seongpil; Nguyễn, Xuân Hùng; Kim, Yong Il; Bang, Boo Hyoung; James, Scott C.; Choi, Joon Hyouk; Yoon, Sam S.

doi:10.1016/j.applthermaleng.2017.09.103

Cited by 29 publications

(3 citation statements)

References 19 publications

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“…By constructing the GNP nano-wicks in the MHP, the heat-transfer rate can be enhanced significantly as the GNPs encourage film-wise evaporation and water circulation due to its ultrafast water permeation property, as depicted in Figure 1 . While there are several studies highlighting the utilization of GNPs in conventional heat pipes [ 55 , 56 , 57 , 58 ], only a handful of studies have utilized this property of GNPs to enhance the thermal performance of MHPs by fully coating the microchannels with GNPs [ 7 , 29 ], achieving excellent enhancement. Most of these studies [ 56 , 57 , 58 ] applied the graphene-based nanofluids as working fluids in the heat pipes where the performance enhancement was not apparent as the enhancement is mainly dependent on the limited deposition of graphene nanoparticles on the pipe wall.…”

Section: Introductionmentioning

confidence: 99%

Remarkable Thermal Performance Enhancement of Micro Heat Pipes with Graphene-Nanoplatelet Nano-Wicks

Gan¹,

Hung²

2023

Nanomaterials

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The ultrafast water permeation property of graphene nanoplatelets (GNPs) synergically enhances the evaporation and water circulation processes in a micro heat pipe (MHP). An MHP is a promising phase-change heat-transfer device capable of transferring large amounts of heat energy efficiently. The hydrophobic, atomically smooth carbon walls of GNPs nanostructures provide a network of nanocapillaries that allows water molecules to intercalate frictionlessly among the graphene layers. Together with the attraction force of the oxygenated functional groups, a series of hydrophobic and hydrophilic surfaces are formed that significantly improve the water circulation rate. The intercalation of water molecules encourages the formation of water-thin film for film-wise evaporation. The effect of nano-wick thickness on the thermal performance of the MHP is investigated. A thinner GNP nano-wick is more favorable to film-wise evaporation while a thicker nano-wick promotes a higher water circulation rate from the condenser to the evaporator, leading to the existence of an optimal thickness. By benchmarking with the uncoated MHP, the thermal conductance of an MHP with a 46.9-µm GNP nano-wick manifests a maximum enhancement of 128%. This study provides insights on the feasible implementation of GNP nano-wicks into a highly efficient micro-scale electronics cooling device for environmental sustainability.

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Section: Introductionmentioning

confidence: 99%

Remarkable Thermal Performance Enhancement of Micro Heat Pipes with Graphene-Nanoplatelet Nano-Wicks

Gan¹,

Hung²

2023

Nanomaterials

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“…The highly water permeative property of GNPs distributes the water over the surface of GNPs-coated substrate to promote filmwise evaporation and facilitates a significantly higher evaporation rate owing to the increased heat transfer area [11,12]. This unique property of graphene-based materials has been effectively applied in the phase-change heat transfer devices, such as two-phase closed thermosyphons [8,9,13], heat pipes [14], micro heat pipes [15,16], microchannels [17,18] and pool boiling systems [10,[19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Effective Passive Phase-Change Light-Emitting Diode Cooling System Using Graphene Nanoplatelets Coatings

et al. 2021

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“…Porosity changes are common in unsaturated porous media. Examples include industrial applications such as personal hygiene tissues (e.g., Sun et al 2015), absorbent polymers (e.g., Brandt et al 1987), cooling systems (e.g., Jo et al 2018), and many others. Geological systems with changing porosity are abundant and include mineral dissolution or precipitation in karst, geothermal, or hydrothermal systems (e.g., Evans and Lizarralde 2003;Waltham et al 2005;Ball et al 2015), thermal or mechanical stress, (e.g., Tsang 1999), bioturbation (e.g., Pérès et al 1998;Gingras et al 2012), diagenetic processes (e.g., Gluyas and Coleman 1992), simple compaction of deposits (Boudreau and Bennett 1999), and radiogenic waste in salt (e.g., Jordan et al 2015a, b, c;Bourret et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Impact of a Porosity-Dependent Retention Function on Simulations of Porous Flow

2018

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Numerical models of flow in unsaturated porous media employ a range of functions to account for capillary effects. In general, these retention functions are assigned at the beginning of the simulation and calculate capillary pressure based on saturation. However, many porous systems involve changes in porosity wherein the retention function should change during the simulation. Model runs which neglect these changes may produce unphysical results such as retention of liquid water in air-filled void spaces. We present a conceptually and numerically simple function that recalculates the retention function at each timestep based on the updated porosity. The new retention function updates the maximum capillary pressure, residual saturation, and maximum saturation prior to applying the saturation fit. We compare results from a fixed (saturation-only) function and the new porosity-dependent retention function through a set of two numerical Gedankenexperiments in salt. The new retention function corrects unphysical model behaviors and causes dramatic changes in simulation behavior relative to the fixed (saturation-only) function, especially when applied to systems dominated by capillary effects. These changes result in large differences in simulated porosity, saturation, and volumetric water content. Water content results obtained using the porositydependent retention function are inverted compared to those obtained from saturation-only functions, with high-porosity nodes changing from very wet when using the saturationonly retention function to very dry when using the porosity-dependent retention function. These test cases suggest that dynamic retention functions in changing-porosity systems are important considerations to ensure sensible simulation results.

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Modifying capillary pressure and boiling regime of micro-porous wicks textured with graphene oxide

Cited by 29 publications

References 19 publications

Remarkable Thermal Performance Enhancement of Micro Heat Pipes with Graphene-Nanoplatelet Nano-Wicks

Remarkable Thermal Performance Enhancement of Micro Heat Pipes with Graphene-Nanoplatelet Nano-Wicks

Effective Passive Phase-Change Light-Emitting Diode Cooling System Using Graphene Nanoplatelets Coatings

Impact of a Porosity-Dependent Retention Function on Simulations of Porous Flow

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