Adsorption-Controlled Thermal Switch Using Nonequilibrium Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Tadeh Avanessian ◽  
Gisuk Hwang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Waste Heat ◽  
Accommodation Coefficient ◽  
Cryogenic Cooling ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Thermal Switch ◽  
Thermal Switches ◽  
The Difference

A thermal switch is a system to control the heat transfer “on/off” for the desired functionalities, and this serves as a basic building block to design advanced thermal management systems in various applications including electronic packaging, waste heat recovery, cryogenic cooling, and new applications such as thermal computers. The existing thermal switches employ the macroscale mechanical-based, relatively slow transient “on/off” switch mechanisms, which may be challenging to provide solutions for micro/nanoscale applications. In this study, a fast and efficient thermal switch mechanism without having extra mechanical controlling system is demonstrated using gas-filled, heterogeneous nanogaps with asymmetric surface interactions in Knudsen regime. Argon gas atoms confined in metal-based solid surfaces are employed to predict the degree of thermal switch, S. Non-equilibrium molecular dynamics simulation is used to create the temperature gradient over the two nanogaps, and the maximum degree of thermal switch is Smax ∼ 13, which results from the difference in adsorption-controlled thermal accommodation coefficient (TAC) and pressure between the two sides of the gaps.

Adsorption-Controlled Thermal Diode: Nonequilibrium Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Tadeh Avanessian ◽  
Gisuk Hwang
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Thermal Management ◽  
Accommodation Coefficient ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Management Systems ◽  
Thermal Switches ◽  
Ar Gas

A thermal diode is a system controlling the heat transfer preferentially in one direction. This serves as a basic building block to design advanced thermal management systems in energy saving applications and to provide implications to design new application such as thermal computers. The development of the thermal diode has been of great interest as electrical diodes have similarly made significant impacts on modern industries. Numerous studies have demonstrated thermal diode mechanisms using non-linear heat transfer mechanisms, but the main challenges in current systems are poor steady-state performance, slow transient response, and/or extremely difficult manufacturing for the viable solutions. In this study, an adsorption-based thermal diode is examined for a fast and efficient thermal diode mechanism as a completely new class, using a gas-filled, heterogeneous nanogap with asymmetric surface interactions in Knudsen regime. Ar gas atoms confined in Pt-based solid surfaces are selected to predict the degree of rectification, R ∼ 10, using non-equilibrium molecular dynamics simulation with the nanogap size of Lz = 20 nm and ΔT = 20 K for various average plate temperatures, 80 < T < 130 K. Different surface energies for the thermal diode is studied and a maximum degree of rectification, Rmax ∼ 10, is found at T = 80 K which results from the significant adsorption-controlled thermal accommodation coefficient (TAC). The obtained results provide insights into the design of advanced thermal management systems including thermal switches and thermal computing systems.

The Edge Effects on the Lattice Thermal Conductivity of Graphene Nanoribbons

2011 ◽  
Author(s):  
Z. Wei ◽  
Z. Ni ◽  
K. Bi ◽  
J. Wang ◽  
Y. Chen
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Graphene Nanoribbons ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Edge Zone ◽  
The Difference ◽  
Nonequilibrium Molecular Dynamics Simulation ◽  
Thermal Conductivities

The thermal conductivity of graphene nanoribbons was investigated with nonequilibrium molecular dynamics simulation methods. The results show that the thermal conductivity of nanoribbons lined with zig-zag edges is higher than that with arm-chair edges for the samples with the same width. The phonon density of states is extracted from the molecular dynamics simulation to quantitatively explain the difference between the thermal conductivities of the two kind nanoribbons. The effects of vacancy on the thermal conductivity of nanoribbons are also investigated and it is found the defects on the edge zone play little role than that located in the interior zone of nanoribbons in reducing thermal conductivities.

Dynamical Behavior and Flow Mechanism of Fluid in Nanochannel by Molecular Dynamics Simulation

2009 ◽  
Author(s):  
Juanfang Liu ◽  
Chao Liu ◽  
Qin Li
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamical Behavior ◽  
Velocity Profiles ◽  
The Other ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Interfacial Region ◽  
Flow Mechanism ◽  
Bulk Fluid

The flow properties and dynamical behavior of fluid in a nanochannel were investigated by nonequilibrium molecular dynamics simulation. First of all, the locale distribution of molecules in the channel is found to be strongly inhomogeneous compared to the bulk fluid. In the vicinity of the wall, portion of the fluid molecules are absorbed on the surface of wall due to the strong interaction of the atoms between the wall and liquid, so that the fluid density in the contact region would be much larger than one of the bulk fluid. But in the other region, the local density value approaches one of the bulk fluids with the increasing distance from the wall. This oscillatory behavior of density resulted in different motion behavior of molecules in the different region of nanochannel. The molecular behavior in the interfacial region is remarkably different from those of fluid atoms in the center of channel and wall atoms, which posses both the motion properties of bulk liquids and a solid atom. At the molecular level, macroscopic continuum hypothesis failed, that is, the results predicted by the Navier-Stoke equations deviate from the simulation data adopted by molecular dynamics simulation. In the paper, the velocity profiles for the channels with different width were plotted, which demonstrated that the time-averaged velocity profiles was not quadratic when the channel width was less than 10 molecular diameters. But on the other cases, the velocity profiles will agree well with the analytical solution based on the NS theory. The molecular dynamics simulation method can withdraw the important microscopical information from the simulation process, which benefit to analyze the flow mechanism at such length scale channel.

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