scholarly journals Effective conductivity of isotropic composite with Kapitza thermal resistance

2018 ◽  
Author(s):  
Kien Trung Nguyen ◽  
Luat Van Nguyen ◽  
Chinh Duc Pham
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Effective Conductivity ◽  
Imperfect Interface ◽  
Simple Method ◽  
Isotropic Composite ◽  
Equivalent Inclusion

A simple method is introduced for computing the effective conductivity of isotropic composite with imperfect interface. Based on the doubly-coated circle assemblage model, one can determine the effective thermal conductivity of the composite. The application of this model to the composite with imperfect interface of the Kapitza's type is proposed. The results obtained were compared with the FFT simulation and the equivalent inclusion approximation in 2D show the effectiveness of the methods.

scholarly journals Estimating the effective conductivity for ellipse-inclusion model with Kapitza thermal resistance

2021 ◽  
Vol 8 ◽  
pp. 16
Author(s):  
Van-Luat Nguyen
Keyword(s):  
Thermal Conductivity ◽  
Fourier Transform ◽  
Thermal Resistance ◽  
Effective Conductivity ◽  
Dimensional Space ◽  
Imperfect Interface ◽  
Two Dimensional ◽  
Imperfect Interfaces ◽  
Equivalent Inclusion ◽  
Resistance Model

The ellipse assemblage model with imperfect interface has quite complex microstructure, that can be considered an extension of the circle assemblage model with imperfect interfaces. The paper introduces an approximate method for computing the effective conductivity of isotropic composites with imperfect interfaces in two-dimensional space. Based on the coated-ellipse assemblage model and the equivalent inclusion approximation, one can determine the effective thermal conductivity of the composites. The polarization approximation is given in an explicit form (PEK) and this method will be applied to calculate the effective conductivity of the composite with Kapitza thermal resistance model. The PEK result will have compared with the Fast Fourier Transform (FFT) simulation and Hashin-strikman bounds (HS).

Computational Evaluation of Effective Conductivity of Particulate Composites with Imperfect Interfaces

2009 ◽  
Vol 631-632 ◽  
pp. 35-40
Author(s):  
M. Zhang ◽  
Peng Cheng Zhai ◽  
Qing Jie Zhang
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Effective Properties ◽  
Effective Conductivity ◽  
Three Dimensional ◽  
Particulate Composite ◽  
Imperfect Interface ◽  
Particulate Composites ◽  
Imperfect Interfaces ◽  
Volume Fractions

This paper is aimed to numerically evaluate the effective thermal conductivity of randomly distributed spherical particle composite with imperfect interface between the constituents. A numerical homogenization technique based on the finite element method (FEM) with representative volume element (RVE) was used to evaluate the effective properties with periodic boundary conditions. Modified random sequential adsorption algorithm (RSA) is applied to generate the three dimensional RVE models of randomly distributed spheres of identical size with the volume fractions up to 50%. Several investigations have been conducted to estimate the influence of the imperfect interfaces on the effective conductivity of particulate composite. Numerical results reveal that for the given composite, due to the existence of an interfacial thermal barrier resistance, the effective thermal conductivity depends not only on the volume fractions of the particle but on the particle size.

Effective Thermal Conductivity of Composites with Different Particle Geometries and Interfacial Thermal Resistance

2010 ◽  
Vol 152-153 ◽  
pp. 269-273
Author(s):  
Mei Zhang ◽  
Peng Cheng Zhai
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Imperfect Interface ◽  
Interfacial Thermal Resistance ◽  
Surface Integral ◽  
Two Phase ◽  
Self Consistent ◽  
Consistent Method ◽  
Barrier Resistance

A new micromechanical method, the weighted residual self-consistent method (WRSCM) is developed to study the effective thermal conductivity of two-phase composites with different particle geometries in the presence of a thermal barrier resistance at the interface between constituents. The imperfect interface involves the continuity of the normal flux but allow for a finite temperature differences across the interface. Within the framework of self-consistent scheme, the effective thermal conductivity of two-phase composite is obtained using numerical iterative method on the basis of a surface integral of temperature over the imperfect interfaces. Numerical results show that for the given composite system, due to the existence of an interfacial thermal resistance, the particle geometries have significant impact on the effective thermal conductivity of composites.

Determining the thermal resistance of a highly insulated wall containing vacuum insulation panels through experimental, calculation and numerical simulation methods

2020 ◽  
pp. 174425912098003
Author(s):  
Travis V Moore ◽  
Cynthia A. Cruickshank ◽  
Ian Beausoleil-Morrison ◽  
Michael Lacasse
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Edge Effect ◽  
3D Simulation ◽  
Simulation Methods ◽  
Zone Method ◽  
Vacuum Insulation ◽  
Thermal Bridges ◽  
Wall Assembly

The purpose of this paper is to investigate the potential for calculation methods to determine the thermal resistance of a wall system containing vacuum insulation panels (VIPs) that has been experimentally characterised using a guarded hot box (GHB) apparatus. The VIPs used in the wall assembly have not been characterised separately to the wall assembly, and therefore exact knowledge of the thermal performance of the VIP including edge effect is not known. The calculations and simulations are completed using methods found in literature as well as manufacturer published values for the VIPs to determine the potential for calculation and simulation methods to predict the thermal resistance of the wall assembly without the exact characterisation of the VIP edge effect. The results demonstrate that disregarding the effect of VIP thermal bridges results in overestimating the thermal resistance of the wall assembly in all calculation and simulation methods, ranging from overestimates of 21% to 58%. Accounting for the VIP thermal bridges using the manufacturer advertised effective thermal conductivity of the VIPs resulted in three methods predicting the thermal resistance of the wall assembly within the uncertainty of the GHB results: the isothermal planes method, modified zone method and the 3D simulation. Of these methods only the 3D simulation can be considered a potential valid method for energy code compliance, as the isothermal planes method requires too drastic an assumption to be valid and the modified zone method requires extrapolating the zone factor beyond values which have been validated. The results of this work demonstrate that 3D simulations do show potential for use in lieu of guarded hot box testing for predicting the thermal resistance of wall assemblies containing both VIPs and steel studs. However, knowledge of the VIP effective thermal conductivity is imperative to achieve reasonable results.

Effective Thermal Conductivity of Functionally Graded Particulate Nanocomposites With Interfacial Thermal Resistance

2008 ◽  
Vol 75 (5) ◽  
Author(s):  
H. M. Yin ◽  
G. H. Paulino ◽  
W. G. Buttlar ◽  
L. Z. Sun
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Functionally Graded ◽  
Interfacial Thermal Resistance ◽  
Conductivity Distribution ◽  
Consistent Model ◽  
The Matrix ◽  
Graded Material ◽  
Perfect Interface

By means of a fundamental solution for a single inhomogeneity embedded in a functionally graded material matrix, a self-consistent model is proposed to investigate the effective thermal conductivity distribution in a functionally graded particulate nanocomposite. The “Kapitza thermal resistance” along the interface between a particle and the matrix is simulated with a perfect interface but a lower thermal conductivity of the particle. The results indicate that the effective thermal conductivity distribution greatly depends on Kapitza thermal resistance, particle size, and degree of material gradient.

scholarly journals Effective thermal conductivity of complicated hierarchic multilayer fabric

2014 ◽  
Vol 18 (5) ◽  
pp. 1613-1618 ◽  
Author(s):  
Jie Fan ◽  
Na Zhu ◽  
Zhi Liu ◽  
Qian Cheng ◽  
Yong Liu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Geometric Feature ◽  
Retention Efficiency

Warm retention property of fabric is one of the most important factors for clothing comfortability. The worm retention efficiency of a multilayer fabric with hierarchic inner structure was investigated based on its geometric feature. The thermal resistance of the multilayer fabric increases as the layer of the fabric increases.

Effective Thermal Conductivity of Submicron Powders: A Numerical Study

2016 ◽  
Vol 846 ◽  
pp. 500-505
Author(s):  
Wei Jing Dai ◽  
Yi Xiang Gan ◽  
Dorian Hanaor
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Granular Materials ◽  
Gas Phase ◽  
Numerical Study ◽  
Transfer Model ◽  
Size Of Particles ◽  
Contact Unit

Effective thermal conductivity is an important property of granular materials in engineering applications and industrial processes, including the blending and mixing of powders, sintering of ceramics and refractory metals, and electrochemical interactions in fuel cells and Li-ion batteries. The thermo-mechanical properties of granular materials with macroscopic particle sizes (above 1 mm) have been investigated experimentally and theoretically, but knowledge remains limited for materials consisting of micro/nanosized grains. In this work we study the effective thermal conductivity of micro/nanopowders under varying conditions of mechanical stress and gas pressure via the discrete thermal resistance method. In this proposed method, a unit cell of contact structure is regarded as one thermal resistor. Thermal transport between two contacting particles and through the gas phase (including conduction in the gas phase and heat transfer of solid-gas interfaces) are the main mechanisms. Due to the small size of particles, the gas phase is limited to a small volume and a simplified gas heat transfer model is applied considering the Knudsen number. During loading, changes in the gas volume and the contact area between particles are simulated by the finite element method. The thermal resistance of one contact unit is calculated through the combination of the heat transfer mechanisms. A simplified relationship between effective thermal conductivity and loading pressure can be obtained by integrating the contact units of the compacted powders.

Effective Thermal Conductivity of Composites with Contact Thermal Resistance between the Inclusions and the Matrix

2020 ◽  
Vol 40 (8) ◽  
pp. 622-627
Author(s):  
I. V. Lavrov ◽  
A. A. Kochetygov ◽  
V. V. Bardushkin ◽  
A. P. Sychev ◽  
V. B. Yakovlev
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Contact Thermal Resistance ◽  
The Matrix
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