Surface Functionalization Mechanisms of Enhancing Heat Transfer at Solid-Liquid Interfaces

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Javier V. Goicochea ◽  
Ming Hu ◽  
Bruno Michel ◽  
Dimos Poulikakos
Keyword(s):  
Heat Flux ◽  
Surface Functionalization ◽  
Heat Dissipation ◽  
Silica Surface ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Liquid Interfaces ◽  
Solid Liquid

Two mechanisms that enhance heat dissipation at solid-liquid interfaces are investigated from the atomistic point of view using nonequilibrium molecular dynamics simulation. The mechanisms include surface functionalization, where –OH terminated headgroups and self-assembled monolayers (SAMs) with different chain lengths are used to recondition and modify the hydrophilicity of silica surface, and vibrational matching between crystalline silica and liquid water, where three-dimensional nanopillars are grown at the interface in the direction of the heat flux with different lengths to rectify the vibrational frequencies of surface atoms. The heat dissipation is measured in terms of the thermal conductance of the solid-liquid interface and is obtained by imposing a one-dimensional heat flux along the simulation domain. A comparison with reported numerical and experimental thermal conductance measurements for similar interfaces indicates that the thermal conductance is enhanced by 1.8–3.2 times when the silica surface is reconditioned with hydrophilic groups. The enhancement is further promoted by SAMs, which results in a 20% higher thermal conductance compared with that of the fully hydroxylated silica surface. Likewise, the presence of nanopillars enhances the interface thermal conductance by 2.6 times compared with a bare surface (without nanopillars). Moreover, for different nanopillar densities, the conductance increases linearly with the length of the pillar and saturates at around 4.26 nm. Changes in the vibrational spectrum of surface atoms and water confinement effects are found to be responsible for the increase in conductance. The modification of surface vibrational states provides a tunable path to enhance heat dissipation, which can also be easily applied to other fluids and interfaces.

Surface Functionalization Mechanisms of Enhancing Heat Transfer at Solid-Liquid Interfaces

2010 ◽  
Author(s):  
Ming Hu ◽  
Javier V. Goicochea ◽  
Bruno Michel ◽  
Dimos Poulikakos
Keyword(s):  
Heat Flux ◽  
Surface Functionalization ◽  
Heat Dissipation ◽  
Silica Surface ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Point Of View ◽  
Nonequilibrium Molecular Dynamics ◽  
Liquid Interfaces ◽  
Solid Liquid

Two mechanisms that increase heat dissipation at solid-liquid interfaces are investigated from the atomistic point of view using nonequilibrium molecular dynamics (NEMD) simulation. The mechanisms include surface functionalization, where −OH terminated headgroups and self-assembled monolayers (SAMs) with different chain lengths are used to recondition and modify the hydrophilicity of silica surface, and vibrational matching between crystalline silica and liquid water, where three-dimensional quartz nanopillars are grown at the interface in the direction of the heat flux with different lengths to rectify the vibrational frequencies of quartz surface atoms. The heat dissipation is measured in terms of the interfacial thermal conductance at the solid-liquid interface, whereas the thermal conductance is obtained by imposing a one-dimensional heat flux across the simulation domain. The heat dissipation is enhanced by a factor of 2 to 3 for both fully hydroxylated and pillar modified surfaces. The SAMs enhance the overall thermal conductance between silica and water further (20% higher thermal conductance compared to the fully hydroxylated silica surface). Moreover, the modification of the vibrational states at the silica surface provides a tunable path to enhance the heat dissipation, which can also be easily applied to other fluids.

For the Growth of 3 Inch D-Shaped GaAs Crystals by a Modified Horizontal Bridgman Process

1993 ◽  
Vol 207 (3) ◽  
pp. 185-195 ◽  
Author(s):  
M H Hsieh ◽  
C C Chieng ◽  
K H Lie ◽  
Y D Guo
Keyword(s):  
Dopant Concentration ◽  
Three Dimensional ◽  
Solidification Process ◽  
Temperature Fields ◽  
Liquid Interfaces ◽  
Axial Distribution ◽  
Mass Transfer Mechanism ◽  
Finite Volume Approach ◽  
Silicon Doped ◽  
Solid Liquid

Doped with silicon or zinc, 3 inch D-shaped GaAs crystals were grown by the modified two-temperature horizontal Bridgman (M2T-HB) technique. Then (1&10) wafers were sliced axially from the chunk of silicon-doped 3 inch GaAs crystals and chemically etched to reveal the growth striations of solid/liquid interfaces. Three-dimensional, numerical simulations of the solidification process for growing 3 inch crystals by the M2T-HB system were performed and compared with the etched (110) wafers from experiments. The heat- and mass-transfer mechanism through the melt is the combination of convection, conduction and radiation. The finite volume approach and the continuum model are employed to determine the position and shape of the interface of the solid/melt, dopant concentration and the temperature field in the crystal and melt. Two methods for computing the dopant concentration are (a) solving the transport equation of full mass concentration and (b) using the simplified model of equilibrium. The computed solidification fronts and the dopant distributions agree successfully with the experimental data, and the axial distribution of dopant concentration as well as flow and temperature fields are computed for information of the crystal quality.

Nano Heat Pipe: Nonequilibrium Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Mohammad Moulod ◽  
Gisuk Hwang
Keyword(s):  
Molecular Dynamics ◽  
Heat Flux ◽  
Heat Pipe ◽  
Thermal Management ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Management Systems ◽  
Working Fluid ◽  
Maximum Heat

A heat pipe has been known as a thermal superconductor utilizing a liquid-vapor phase change, and it has drawn significant attentions for advanced thermal management systems. However, a challenge is the size limitation, i.e., the heat pipe cannot be smaller than the evaporator/condenser wick structures, typically an order of micron, and a new operating mechanism is required to meet the needs for the nanoscale thermal management systems. In this study, we design the nanoscale heat pipe employing the gas-filled nanostructure, while transferring heat via ballistic fluid-particle motions with a possible returning working fluid via surface diffusions along the nanostructure. The enhanced heat flux for the nano heat pipe is demonstrated using the nonequilibrium molecular dynamics simulations (NEMDS) for the argon gas confined by the 20 nm-long Pt nanogap with a post wall with the temperature difference between the hot and cold surfaces of 20 K. The predicted results show that the maximum heat flux through the gas-filled nanostructure (heat pipe) nearly doubles that of the nanogap without the post wall at 100 < T < 140 K. The optimal operating conditions/material selections are discussed. The results for the nanogap agree with those obtained from the kinetic theory, and provide insights into the design of advanced thermal management systems.

scholarly journals Nonequilibrium molecular dynamics simulations of nanoconfined fluids at solid-liquid interfaces

2017 ◽  
Vol 146 (24) ◽  
pp. 244507 ◽  
Author(s):  
M. Morciano ◽  
M. Fasano ◽  
A. Nold ◽  
C. Braga ◽  
P. Yatsyshin ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nonequilibrium Molecular Dynamics ◽  
Liquid Interfaces ◽  
Dynamics Simulations ◽  
Solid Liquid

scholarly journals Monte Carlo analysis of frequency domain thermoreflectance data for quantitative measurement of interfacial thermal conductance at solid-liquid interfaces modified with self-assembled monolayers

2021 ◽  
Vol 2116 (1) ◽  
pp. 012042
Author(s):  
Kenny Yu ◽  
Ryan Enright ◽  
David McCloskey
Keyword(s):  
Monte Carlo ◽  
Thermal Conductance ◽  
Work Of Adhesion ◽  
Self Assembled Monolayers ◽  
Liquid Interfaces ◽  
Confidence Bounds ◽  
Interfacial Thermal Conductance ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Solid Liquid

Abstract A Monte Carlo method, implemented for quantifying confidence bounds on thermoreflectance (TR) measurements of interfacial thermal conductance G at solid-liquid interfaces modified with self-assembled monolayers (SAMs) is presented in this paper. Here we used 1-decanethiol (1DT) and 1H,1H,2H,2H-Perfluorodecanethiol (PFDT) SAMs to achieve two distinct work of adhesion. Using TR measurements in conjunction with Monte Carlo simulations, we determined G values to be 51 ± 7 MWm-2K-1, 58 ± 8 MWm-2K-1, and 72 ± 17 MWm-2K-1 for Au-PFDT-H2O, Au-1DT-H2O, and Au-H2O, respectively. Our results with the new confidence bounds position our experimental data on surfaces modified with SAMs comparable to literature. However, contrary to previous results shown in the literature, our data showed that a significant decrease in G can be seen for DI water on bare Au that was exposed in ambient for extended period. Our results indicate that G could be influenced by factors beyond a simple work of adhesion, an indication also seen from the work of Park et al.. To solidify this finding, further investigation is necessary to better understand G dependence on surface wettability.

Thermal conductance bottleneck of a three dimensional graphene–CNT hybrid structure: a molecular dynamics simulation

2020 ◽  
Vol 22 (1) ◽  
pp. 337-343 ◽  
Author(s):  
Zepei Yu ◽  
Yanhui Feng ◽  
Daili Feng ◽  
Xinxin Zhang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Thermal Transport ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Hybrid Structure ◽  
Dynamics Simulation ◽  
Atomistic Structure

We observed the atomistic structure of the junction to study mechanism governing the thermal transport across GCNT.

Thermal Conductivity of Graphene on Nanostructure Size from Nonequilibrium Molecular Dynamics Simulations

2020 ◽  
Vol 17 (4) ◽  
pp. 1566-1570
Author(s):  
Xianqi Wei ◽  
Zelin Li ◽  
Junchen Lu ◽  
Shunlong Xu ◽  
Yuancheng Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Management ◽  
Strong Dependence ◽  
Thermal Conductance ◽  
Mean Free Path ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Edge Type ◽  
Dynamics Simulations

Thermal transport of graphene occupies a unique place in thermal management of electronic devices, especially for nanosize devices with high-density integration and high dissipated power. The structure of graphene on nanometer scale changes its thermal conductance. Here, the thermal characters of graphene have been researched by nonequilibrium molecular dynamics simulation (NEMDS) at room temperature. Special attention is focused on the edge type (zigzag or armchair) and nanostructure size dependence of conductivity for heat. The consequences suggest that the thermal conductivity of zigzag edge has been higher than that of armchair, which is because of the higher phonon group velocities. Furthermore, thermal conductivity shows a rising tendency, when the model is calculated from length of 21.84 nm to 43.78 nm. The result indicates that the thermal property performs a strong dependence on nanostructure size which is less than phonon mean free path (775 nm). Our research highlights the significance of structure attribute relationships together with providing useful guideline in calculations for nanosize devices thermal management.

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