Fluctuation–dissipation analysis of nonequilibrium thermal transport at the hydrate dissociation interface

2019 ◽  
Vol 21 (42) ◽  
pp. 23492-23500 ◽  
Author(s):  
Jia Li ◽  
Zhao-Liang Wang
Keyword(s):  
Heat Flux ◽  
Thermal Transport ◽  
Thermal Fluctuation ◽  
Nonequilibrium Process ◽  
Hydrate Dissociation ◽  
Fluctuation Dissipation

Thermal fluctuation–dissipation at the interface is justified in the nonequilibrium process of hydrate dissociation in terms of heat flux.

Thermal Transport through Solid-Solid Interface with an Interlayer

2011 ◽  
Vol 483 ◽  
pp. 750-754
Author(s):  
Ya Dong Liu ◽  
Ke Dong Bi ◽  
Yun Fei Chen ◽  
Min Hua Chen
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
System Size ◽  
Simulation System ◽  
Nonequilibrium Molecular Dynamics ◽  
Solid Interface ◽  
Interface Thermal Resistance ◽  
System Temperature

Nonequilibrium molecular dynamics (NEMD) approach is developed to investigate the thermal transport across a solid-solid interface between two different materials with an interlayer around it. The effects of system size and the interlayer material’s properties on the interface thermal resistance are considered in our model. The NEMD simulations show that the addition of an interlayer between two highly dissimilar lattices depresses the interface thermal resistance effectively. Meanwhile, the effective thermal conductivity along the direction of heat flux is enhanced with the increasing system temperature. Moreover, the interface thermal resistance after including an interlayer does not depend strongly on the simulation system size.

scholarly journals Thermal Transport in One-Dimensional Van Der Waals Heterostructures: Effects of Coating Layers on the Thermal Conductivity of Carbon Nanotubes

2020 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Yao Du ◽  
Zheng Zhong
Keyword(s):  
Heat Flux ◽  
Thermal Transport ◽  
Van Der Waals ◽  
Thermal Conductance ◽  
One Dimensional ◽  
Interfacial Thermal Conductance ◽  
Quantitative Understanding ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Individual

In this paper, we conduct a comprehensive investigation on the thermal transport in one-dimensional (1D) van der Waals (vdW) heterostructures by using non-equilibrium molecular dynamics simulations. It is found that the boron nitride nanotube (BNNT) coating can increase the thermal conductance of inner carbon nanotube (CNT) base by 36%, while the molybdenum disulfide nanotube (<a>MSNT</a>) coating can reduce the thermal conductance by 47%. The different effects of BNNT and MSNT coatings on the thermal transport behaviors of 1D vdW heterostructures are explained by the competition mechanism between improved heat flux and increased temperature gradient in 1D vdW heterostructures. By taking CNT@BNNT@MSNT as an example, thermal transport in 1D vdW heterostructures containing three layers is also investigated. It is found that the coaxial BNNT-MSNT coating can significantly reduce the thermal conductance of inner CNT base by 61%, which is even larger than that of an individual MSNT coating. This unexpected reduction in thermal conductance of CNT@BNNT@MSNT can be explained by the suppression of heat flux arising from the possible compression effect, since BNNT-MSNT coating in CNT@BNNT@MSNT can more significantly suppress the vibration of inner CNT when compared to the individual MSNT coating in CNT@MSNT. In addition to the in-plane thermal transport, the interfacial thermal conductance between inner and outer nanotubes in 1D vdW heterostructures is also examined to provide a quantitative understanding of the thermal transport behaviors of1D vdW heterostructures. This work is expected to provide molecular insights into tailoring the heat transport in carbon base 1D vdW heterostructures and thus facilitate their broader applications as thermal interface materials.

Analysis of Laminar Slip-Flow Thermal Transport in Microchannels With Transverse Rib and Cavity Structured Superhydrophobic Walls at Constant Heat Flux

2011 ◽  
Author(s):  
D. Maynes ◽  
B. W. Webb ◽  
V. Soloviev
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Thermal Transport ◽  
Peclet Number ◽  
Average Nusselt Number ◽  
Slip Flow ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Péclet Number

This paper presents an analytical investigation of the thermally developing and periodically fully-developed flow in a parallel-plate channel comprised of superhydrophobic walls. The superhydrophobic walls considered in this paper exhibit alternating micro-ribs and cavities positioned perpendicular to the flow direction and the transport scenario analyzed is that of constant wall heat flux through the rib surfaces with negligible thermal transport through the vapor cavity interface. Axial conduction is neglected in the analysis and the problem is one of Graetz flow with apparent slip-flow and periodicity of constant heating. Closed form solutions for the local Nusselt number and wall temperature are presented and are in the form of infinite series expansions. Previously it has been shown that significant reductions in the overall frictional pressure drop can be expected relative to the classical smooth channel laminar flow. The present results reveal that the overall thermal transport is markedly influenced by the relative cavity region (cavity fraction), the relative rib/cavity module width, and the flow Peclet number. The following conclusions can be made regarding thermal transport for a constant heat flux channel exhibiting the superhydrophobic surfaces considered: 1) Increases in the cavity fraction lead to decreases in the average Nusselt number; 2) Increasing the relative rib/cavity module length yields a decrease in the average Nusselt number; and 3) as the Peclet number increases the average Nusselt number increases. For all parameters explored, the limiting upper bound on the fully-developed average Nusselt number corresponds to the limiting case scenario of classical laminar flow through a smooth-walled channel with constant heat flux.

Electron thermal transport in laser-target plasmas on the basis of Grad's 13-moment transport equations

1988 ◽  
Vol 39 (1) ◽  
pp. 115-138 ◽  
Author(s):  
T. J. M. Boyd ◽  
R. D. Lonsdale ◽  
J. J. Sanderson
Keyword(s):  
Heat Flux ◽  
Classical Theory ◽  
Thermal Transport ◽  
Fluid Model ◽  
Moment Theory ◽  
Slab Geometry ◽  
General Behaviour ◽  
Laser Target ◽  
Suprathermal Electrons ◽  
Collisionless Plasmas

Grad's 13-moment theory is used to model thermal transport in laser-produced plasmas where conditions are such that one may not assume that the plasma is collision-dominated. The equations are presented for a multi-fluid model in slab geometry and are solved numerically for various cases. Comparisons are made with classical theory and with simulations of collisionless plasmas. Results show that, although there are differences between 13-moment and classical predictions, the two theories agree on the general behaviour of the plasma. In particular, 13-moment theory fails to explain the heat-flux inhibition implied by some experimental observations. The theory has also been applied to model thermal transport in plasmas with a population of suprathermal electrons.

An experimental study of the effect of uniform strain on thermal fluctuations in grid-generated turbulence

1980 ◽  
Vol 99 (3) ◽  
pp. 545-573 ◽  
Author(s):  
Z. Warhaft
Keyword(s):  
Heat Flux ◽  
Decay Rate ◽  
Time Scale ◽  
Cross Correlation ◽  
Thermal Fluctuation ◽  
Thermal Fluctuations ◽  
Length Scale ◽  
Scale Size ◽  
Velocity Scale ◽  
Scale Ratio

The effect of homogeneous strain on passive scalar fluctuations, and the resultant evolution of the scalar field when the strain is removed, is experimentally studied by passing thermal fluctuations in decaying grid turbulence through a four-to-one axisymmetric contraction. Using amandoline(Warhaft & Lumley 1978a) to vary the scale size of the initial thermal fluctuations and hence the pre-contraction mechanical/thermal time-scale ratio,r, it is shown, for values ofrgreater than unity, that asris increased so is the post-contraction thermal decay rate, i.e. the contraction does not cause the thermal-fluctuation decay rate to equilibrate to a constant value. In these experiments the post-contraction thermal decay rate is always greater than the pre-contraction decay rate, i.e. the contraction accelerates the thermal-fluctuation decay. Moreover, the mechanical/thermal time-scale ratio in the post-contraction region is driven further from unity. In terms of scale size the uniform strain has the effect of increasing the thermal length scale by an amount equal in value to the contraction ratio if the pre-contraction thermal length scale is comparable to that of the pre-contraction velocity scale. However, if the pre-contraction thermal length scale is smaller than the pre-contraction velocity scale then the effect of the contraction on the thermal scale is less marked. The contraction induces significant negative cross-correlation ρuθbetween the longitudinal velocityuand thermal fluctuations θ even if the pre-contraction cross-correlation is close to zero. The magnitude of ρuθand hence the post-contraction heat flux is varied and the coherence structure is studied. It is shown that the thermal-fluctuation decay rate is insensitive to the magnitude of the heat flux, the latter of which decays rapidly compared to the relatively slow decay of turbulence energy in the post-contraction region. It is also shown that ρuθtends towards zero in this axisymmetric homogeneous flow at a faster rate than in isotropic turbulence. In accord with previous investigations, the return toward isotropy of the velocity field is very slow.

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