A Molecular Dynamics Study on the Effects of Nanostructural Clearances on Thermal Resistance at a Liquid-Solid Interface

2009 ◽  
Author(s):  
Masahiko Shibahara ◽  
Kiyoshi Takeuchi
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Surface Area ◽  
Solid Wall ◽  
Potential Parameter ◽  
Liquid Region ◽  
Solid Interface ◽  
Dynamics Simulations ◽  
Geometric Surface ◽  
Geometric Surface Area

The effects of the surface structures and the surface structural clearances at the nanometer scale on the thermal resistance at a liquid water-solid interface, as well as the dynamic behaviors of liquid molecules, were investigated directly by the classical molecular dynamics simulations. The thermal resistance between the solid wall and the liquid region was calculated by the temperature discontinuity at a liquid-solid interface and the energy flux that was added or subtracted by the Langevin method per unit area so as to maintain a constant solid wall temperature. When the potential parameter between liquid molecules and nanostructure atoms is equal to that between liquid molecules and solid wall atoms, the geometric surface area change depending on the nanostructures as well as their clearances and the dynamic behaviour change of the fluid molecules at the interface depending on the nanostructural clearances cause the thermal resistance reduction depending on the nanostructures at the liquid-solid interface. When the potential parameter between liquid molecules and nanostructure atoms is different from that between liquid molecules and solid wall atoms, the thermal resistance at the interface is dependent on the potential parameter between liquid molecules and nanostructure atoms rather than the geometric surface area in a molecular scale depending on the nanostructures as well as their clearances.

A Molecular Dynamics Study on the Effects of Nanostructural Clearances on Thermal Resistance at a Liquid-Solid Interface

2010 ◽  
Author(s):  
Masahiko Shibahara ◽  
Kiyoshi Takeuchi
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Surface Area ◽  
Solid Wall ◽  
The Self ◽  
Potential Parameter ◽  
Self Diffusion ◽  
Solid Interface ◽  
Geometric Surface ◽  
Geometric Surface Area

The effects of the surface structures and the surface structural clearances at the nanometer scale on the thermal resistance at a liquid water-solid interface, as well as the self-diffusion behaviors of liquid molecules, were investigated directly by the non-equilibrium classical molecular dynamics simulations. When the potential parameter between liquid molecules and nanostructure atoms is equal to that between liquid molecules and solid wall atoms, the geometric surface area change depending on the nanostructures as well as their clearances and the self-diffusion coefficient change of the liquid molecules at the interface depending on the nanostructural clearances cause the thermal resistance change depending on the nanostructures at the liquid-solid interface. When the potential parameter between liquid molecules and nanostructure atoms is different from that between liquid molecules and solid wall atoms, the interfacial thermal resistance is dependent on the potential parameter between liquid molecules and nanostructure atoms itself rather than the geometric surface area in a molecular scale.

A Molecular Dynamics Study on Effects of Nanostructural Clearances at an Interface on Thermal Resistance

2008 ◽  
Author(s):  
Masahiko Shibahara ◽  
Kosuke Inoue ◽  
Kiyomori Kobayashi
Keyword(s):  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Thermal Resistance ◽  
Solid Wall ◽  
Middle Layer ◽  
Dynamics Simulation ◽  
Nanometer Scale ◽  
Liquid Density ◽  
Solid Interface ◽  
Solid Walls

The classical molecular dynamics simulation was conducted in order to clarify the effects of structural clearances in nanometer scale on thermal resistance at a liquid-solid interface. A liquid molecular region confined between the solid walls, of which the interparticle potential was Lennard-Jones type, was employed as a calculation system. The solid walls consisted of three atomic layers where the temperature of the middle layer was controlled by the Langevin method. Heat flux in the system was calculated numerically by integrating the forces that acted on the temperature controlled atoms by the Langevin method. The temperature jump between the solid wall and the liquid molecular region was calculated numerically. The thermal resistance at a liquid-solid interface was calculated numerically with changing the surface structural clearances in nanometer scale. Temperature gradient and liquid density were also changed as calculation parameters. With changing the surface structural clearances from 0nm to 2.5nm the thermal resistance at the interface once decreased and became the minimum value when the structural clearances were between 0.6 to 1.0 nm. The thermal resistance between the solid and the liquid increased when the structural clearances were more than 1.0nm. With the increase of the liquid density the thermal resistance between the solid and the liquid substantially decreased regardless of the temperature gradient and the surface structures in nanometer scale.

Molecular Dynamics Simulations of Thermal Transport at the Nanoscale Solid-Liquid Interface

2013 ◽  
Vol 291-294 ◽  
pp. 1999-2003 ◽  
Author(s):  
Zhi Hai Kou ◽  
Min Li Bai ◽  
Guo Chang Zhao
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Molecular Dynamics Simulations ◽  
Solid Wall ◽  
Liquid Interface ◽  
Heat Fluxes ◽  
Interfacial Thermal Resistance ◽  
Dynamics Simulations ◽  
Solid Liquid Interface ◽  
Solid Liquid

Simulation of nanoscale thermo-fluidic transport has attracted considerable attention in recent years owing to rapid advances in nanoscience and nanotechnology. The three- dimensional molecular dynamics simulations are performed for the system of a liquid layer between two parallel solid walls at different wall temperatures. The solid-solid interaction is modeled by the embedded atom method. The heat flux through the solid-liquid interface is calculated by Green-Kubo method. The effects of interface wettability and wall temperature on the interfacial thermal resistance are also analyzed. It is found that there exist the relatively immobile quasi-crystalline interfacial layers close to each solid wall surface with higher number density and thus higher local thermal conductivity than the corresponding liquid phase. The interfacial thermal resistance length is overestimated by 8.72% to 19.05% for the solid-solid interaction modeled by the Lennard-Jones potential, and underestimated based on heat fluxes calculated by Fourier equation.

A Molecular Dynamics Study on Effects of Nanostructural Clearances on Thermal Resistance at an Interface Between Liquid and Solid

2008 ◽  
Author(s):  
Masahiko Shibahara ◽  
Kiyoshi Takeuchi
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Surface Area ◽  
Resistance Index ◽  
Dynamics Simulation ◽  
Fluid Density ◽  
Resistance Change ◽  
Molecular Scale ◽  
Dynamics Simulations ◽  
Solid Walls

The classical molecular dynamics simulation was conducted in order to clarify the effects of the surface structural clearances in nanometer scale on thermal resistance at a liquid-solid interface as well as static and dynamic behaviours of fluid molecules in the vicinity of the surface. A liquid molecular region confined between the solid walls, of which the interparticle potential was Lennard-Jones type, was employed as a calculation system. The thermal resistance between the liquid molecular region and the solid walls with nanostructures was calculated by the heat flux and the temperature jump obtained in the molecular dynamics simulations. With changing the surface structural clearances from 0 to 2.81 nm the thermal resistance between the liquid molecular region and the solid walls with nanostructures once decreased and became the minimum value when the structural clearances were about 0.7 nm. Surface area in molecular scale and fluid density at the interface were dependent on the surface structural clearances and the thermal resistance index calculated by the relative surface area in molecular scale and the relative fluid density at the interface could predict thermal resistance change depending on the nanostructural clearances. Surface nanostructural clearances affected the fluid molecular motions along the heat transfer direction only when the molecular velocity was averaged over a specific characteristic time. Surface nanostructural clearances affected the diffusion behaviours of fluid molecules in the vicinity of the surface too.

Molecular Dynamics Study on the Influences of Nanoparticle Adherent Layer on Interfacial Thermal Resistance at a Liquid-Solid Interface

2013 ◽  
Author(s):  
Masahiko Shibahara ◽  
Tatsuya Koike
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Interaction Potential ◽  
Interfacial Thermal Resistance ◽  
Molecular Density ◽  
Solid Interface ◽  
Nanoparticle Layer ◽  
Parametric Studies ◽  
Dynamics Simulations ◽  
Potential Parameters

The influences of a nanoparticle layer adherent to a surface on the thermal resistance at a liquid-solid interface were investigated by non-equilibrium classical molecular dynamics simulations. The interaction potential parameters between the liquid molecules and the wall atoms and those between the liquid molecules and the nanoparticle atoms were changed for the parametric studies. The variation of the interfacial thermal resistance caused by a nanoparticle layer was observed depending on the interaction potential parameter between the liquid molecules and the nanoparticle atoms and that between the liquid molecules and the surface atoms as well as the nanoparticle adherent density. Such variations of the interfacial thermal resistance caused by the nanoparticle adherent layer can be explained by the variation of the liquid molecular density profile at the liquid-solid interface.

Hydrophobic hydrogen anode with a nickel catalyst

1982 ◽  
Vol 47 (12) ◽  
pp. 3230-3235 ◽  
Author(s):  
Olga Marholová ◽  
Karel Smrček
Keyword(s):  
Surface Area ◽  
Nickel Catalyst ◽  
Raney Nickel ◽  
Platinum Catalyst ◽  
Raney Nickel Catalyst ◽  
Electrochemical Parameters ◽  
Geometric Surface ◽  
Geometric Surface Area ◽  
Hydrogen Anode ◽  
In Cells

A hydrophobic porous hydrogen anode was prepared whose electrochemical parameters are comparable with anodes containing a platinum catalyst. For its successful preparation, oxidation of the Raney nickel catalyst with air oxygen or with fluorine from Teflon must be prevented. The electrodes of a geometric surface area up to 450 cm2 were tested in cells and modules filled with 7M-KOH.

Molecular Dynamics Simulations of Interfacial Heat and Mass Transfer at Nanostructured Surface

2007 ◽  
Author(s):  
Gyoko Nagayama ◽  
Masako Kawagoe ◽  
Takaharu Tsuruta
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Boundary Condition ◽  
Thermal Resistance ◽  
Hydrodynamic Resistance ◽  
Hydrophilic Surface ◽  
Dynamics Simulations ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
The Continuum

The nanoscale heat and mass transport phenomena play important roles on the applications of nanotechnologies with great attention to its differences from the continuum mechanics. In this paper, the breakdown of the continuum assumption for nanoscale flows has been verified based on the molecular dynamics simulations and the heat transfer mechanism at the nanostructured solid-liquid interface in the nanochannels is studied from the microscopic point of view. Simple Lennard-Jones (LJ) fluids are simulated for thermal energy transfer in a nanochannel using nonequilibrium molecular dynamics techniques. Multi-layers of platinum atoms are utilized to simulate the solid walls with arranged nanostructures and argon atoms are employed as the LJ fluid. The results show that the interface structure (i.e. the solid-like structure formed by the adsorption layers of liquid molecules) between solid and liquid are affected by the nanostructures. It is found that the hydrodynamic resistance and thermal resistance dependents on the surface wettability and for the nanoscale heat and fluid flows, the interface resistance cannot be neglected but can be reduced by the nanostructures. For the hydrodynamic boundary condition at the solid-liquid interface, the no-slip boundary condition holds good at the super-hydrophilic surface with large hydrodynamic resistance. However, apparent slip is observed at the low hydrodynamic resistance surface when the driving force overcomes the interfacial resistance. For the thermal boundary condition, it is found that the thermal resistance at the interface depends on the interface wettability and the hydrophilic surface has lower thermal resistance than that of the hydrophobic surfaces. The interface thermal resistance decreases at the nanostructed surface and significant heat transfer enhancement has been achieved at the hydrophilic nanostructured surfaces. Although the surface with nanostrutures has larger surface area than the flat surface, the rate of heat flux increase caused by the nanostructures is remarkable.

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