LOW TEMPERATURE THERMAL CONDUCTIVITY OF TWO NATURAL DIAMONDS : ANISOTROPIC HEAT CONDUCTION IN THE BOUNDARY SCATTERING REGIME

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-1017-C6-1018 ◽  
Author(s):  
J. W. Vandersande
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Low Temperature ◽  
Boundary Scattering ◽  
Natural Diamonds ◽  
Anisotropic Heat Conduction

scholarly journals Lattice Boltzmann method simulation of the gas heat conduction of nanoporous material

2020 ◽  
Vol 24 (6 Part A) ◽  
pp. 3749-3756
Author(s):  
Ya Han ◽  
Shuai Li ◽  
Hai-Dong Liu ◽  
Weipeng Cui
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Boltzmann Method ◽  
Knudsen Number ◽  
Lattice Boltzmann ◽  
Size Effects ◽  
Temperature Jump ◽  
Boundary Scattering ◽  
Nanoporous Material ◽  
Boltzmann Method

In order to deeply investigate the gas heat conduction of nanoporous aerogel, a model of gas heat conduction was established based on microstructure of aerogel. Lattice Boltzmann method was used to simulate the temperature distribution and gas thermal conductivity at different size, and the size effects of gas heat conduction have had been obtained under micro-scale conditions. It can be concluded that the temperature jump on the boundary was not obvious and the thermal conductivity remained basically constant when the value of Knudsen number was less than 0.01; as the value of Knudsen number increased from 0.01 to 0.1, there was a clear temperature jump on the boundary and the thermal conductivity tended to decrease and the effect of boundary scattering increased drastically, as the value of Knudsen number was more than 0.1, the temperature jump increased significantly on the boundary, furtherly, the thermal conductivity decreased dramatically, and the size effects were significantly.

Thermal Conductivity of Nanochanneled Alumina

2000 ◽  
Author(s):  
A. R. Kumar ◽  
D.-A. Achimov ◽  
T. Zeng ◽  
G. Chen
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Experimental Study ◽  
Heat Conduction ◽  
Room Temperature ◽  
Conduction Model ◽  
Heat Conduction Model ◽  
Anisotropic Heat Conduction ◽  
3Ω Technique

Abstract We present an experimental study on the thermal conductivity of anodized alumina with regular nanochannels. Thermal conductivity values in both directions parallel and perpendicular to the nanochannel axis are measured at room temperature using the 3ω technique. An anisotropic heat conduction model is developed to analyze the experimental data.

scholarly journals Effects of anisotropic composite skin on electrothermal anti-icing system

2019 ◽  
Vol 233 (14) ◽  
pp. 5403-5413 ◽  
Author(s):  
Xiaobin Shen ◽  
Xiaochuan Liu ◽  
Guiping Lin ◽  
Xueqin Bu ◽  
Dongsheng Wen
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Water Film ◽  
Transfer Model ◽  
Anisotropy Axis ◽  
Mass Model ◽  
Conduction Model ◽  
Anisotropic Thermal Conductivity ◽  
Anisotropic Heat Conduction ◽  
Heat And Mass Model

To study the effects of anisotropic thermal conductivity of composite aircraft skin on the heat transfer characteristics of electrothermal anti-icing system, the differential equation of anisotropic heat conduction was established using coordinate transformation of principal anisotropy axis. In addition, it was coupled with the heat and mass transfer model of the runback water film on the anti-icing surface to perform numerical simulation of the electrothermal anti-icing system. The temperature results of the vertical and cylindrical orthotropic thermal conduction in the rectangular and semi-cylindrical composite skin were consistent with those obtained by the traditional orthotropic model, which verified the anisotropic heat conduction model. The temperature distribution of anti-icing surface agreed well with the literature data, which validated the coupled heat and mass model of the runback water flow and the anisotropic skin. The anisotropic thermal conductivity of composite skin would make temperature change more gradual, and the effect was more significant where the curvature of the temperature curve was greater. However, the anti-icing surface of the electrothermal anti-icing system was slightly affected by the anisotropic heat conduction of the multilayered composite skin.

Anisotropic Heat Conduction in Cubic Crystals in the Boundary Scattering Regime

1970 ◽  
Vol 2 (10) ◽  
pp. 4077-4083 ◽  
Author(s):  
A. K. McCurdy ◽  
H. J. Maris ◽  
C. Elbaum
Keyword(s):  
Heat Conduction ◽  
Boundary Scattering ◽  
Cubic Crystals ◽  
Anisotropic Heat Conduction

scholarly journals Effect of In-Plane Aspect Ratio of Graphene Filler on Anisotropic Heat Conduction in Paraffin/Graphene Composite

2021 ◽  
Author(s):  
Hiroki Matsubara ◽  
Taku Ohara
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Aspect Ratio ◽  
Thermal Management ◽  
Graphene Composite ◽  
Molecular Scale ◽  
Anisotropic Heat Conduction

Enhancement of polymer thermal conductivity by nanographene fillers and clarification of its molecular-scale mechanisms are of great concern in the development of advanced thermal management materials. In the present study,...

A Broad Range of Phonon Mean Free Paths Is Important for Heat Conduction

2008 ◽  
Author(s):  
C. Dames
Keyword(s):  
Thermal Conductivity ◽  
Distribution Function ◽  
Heat Conduction ◽  
Mean Free Path ◽  
Angular Frequency ◽  
Boundary Scattering ◽  
Spectral Form ◽  
Einstein Distribution ◽  
K 13 ◽  
Bose Einstein

The thermal conductivity is modeled with a spectral form of kinetic theory k=13∫CωνLdω(1) where ω is the angular frequency, Cω is the specific heat per unit frequency, ν = ∂ω/∂q is the group velocity, and L is the effective mean free path (MFP) which combines bulk and boundary scattering using Matthiessen’s rule: Cω=ħωDOS∂f/∂T(2)L−1=Lbulk−1+Lboundary−1.(3) Here q is the wavevector, DOS is the density of states (acoustic modes only), T is the temperature, and f is the Bose-Einstein distribution function.

scholarly journals APPROXIMATE ANALYTICAL SOLUTION OF THE PROBLEM OF CONJUGATE HEAT TRANSFER BETWEEN THE BOUNDARY LAYER AND THE ANISOTROPIC STRIP

2019 ◽  
Vol 16 (32) ◽  
pp. 572-582
Author(s):  
Vladimir F. FORMALEV ◽  
Sergey A. KOLESNIK ◽  
Ekaterina L. KUZNETSOVA
Keyword(s):  
Thermal Conductivity ◽  
Boundary Layer ◽  
Heat Conduction ◽  
Analytical Solution ◽  
Integral Transform ◽  
External Boundary ◽  
Interface Boundary ◽  
Heat Flows ◽  
Anisotropic Heat Conduction ◽  
Longitudinal Variable

Optimization of technological processes in metallurgy related to transfer and use of heat energy makes more complicated demands for calculation of heat exchange. Therefore, the work, the approximate analytical method for solving the conjugate problems of viscous gas-dynamic boundary layer and thermal conductivity in the anisotropic strip, has been developed. The paper uses modern numerical methods for solving differential equations in partial derivative and analytic methods on the basis of an integral transform of Fourier and Laplace. Boundary equations have been solved analytically with certain simplifications, and the problem of anisotropic heat conduction has been solved analytically. The heat flows are determined analytically by the longitudinal variable at the interface boundary. It has been established that temperature increase of the external surface contributes to that all factors directly impacting on the magnitude of heat flows act towards their reduction. The analytical solution for the problem of thermal conductivity in the anisotropic strip with a general type of anisotropy when the heat flows from the boundary layer are determined at the boundaries is obtained. The conducted research for the temperature of external boundary and heat flow from gas to it demonstrates that with increasing the degree of longitudinal anisotropy the surface temperature of the strip downstream increases from increasing longitudinal heat conduction An original conjugation method using the continuous heat flows, and temperatures at the interface boundary is found. The numerical results for the heat flows and temperatures at the interface boundary have been obtained and analyzed.

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