scholarly journals Thermal Conductivity of the Moist Porous Material.

Netsu Bussei ◽  
1993 ◽  
Vol 7 (3) ◽  
pp. 177-182
Author(s):  
Shuichi Hokoi ◽  
Mamoru Matsumoto
Keyword(s):  
Thermal Conductivity ◽  
Porous Material ◽  
Moist Porous Material

scholarly journals Thermal conductivity of unsaturated clay-rocks

2010 ◽  
Vol 14 (1) ◽  
pp. 91-98 ◽  
Author(s):  
D. Jougnot ◽  
A. Revil
Keyword(s):  
Thermal Conductivity ◽  
Porous Material ◽  
Solid Phase ◽  
Model Parameters ◽  
Electrical Parameters ◽  
New Model ◽  
Unsaturated Clay ◽  
Unsaturated Porous Material ◽  
Clay Rocks ◽  
Good Agreement

Abstract. The parameters used to describe the electrical conductivity of a porous material can be used to describe also its thermal conductivity. A new relationship is developed to connect the thermal conductivity of an unsaturated porous material to the thermal conductivity of the different phases of the composite, and two electrical parameters called the first and second Archie's exponents. A good agreement is obtained between the new model and thermal conductivity measurements performed using packs of glass beads and core samples of the Callovo-Oxfordian clay-rocks at different saturations of the water phase. We showed that the three model parameters optimised to fit the new model against experimental data (namely the thermal conductivity of the solid phase and the two Archie's exponents) are consistent with independent estimates. We also observed that the anisotropy of the effective thermal conductivity of the Callovo-Oxfordian clay-rock was mainly due to the anisotropy of the thermal conductivity of the solid phase.

Effects of Heat Treatment on Thermal Conductivity of Highly Porous Copper/Silver Systems

2007 ◽  
Author(s):  
Brian A. Murtha ◽  
Anil K. Kulkarni ◽  
Jogender Singh
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Porous Material ◽  
Grain Boundaries ◽  
Phonon Scattering ◽  
Particle Diffusion ◽  
Conductive Heat ◽  
Material Particle ◽  
Highly Porous ◽  
Highly Porous Material

The phenomenon of sintering has a significant impact on the thermal conductivity of a highly porous material. Particle diffusion greatly reduces the number of grain boundaries that are normally present in porous materials. In turn, fewer grain boundaries imply fewer sites for phonon scattering during conductive heat transfer. Therefore, during heat treatment of a highly porous material, particle diffusion accounts for a changing thermal conductivity. This occurs with no bulk densificiation of the material. In fact, SEM images show that the microstructure of a porous material changes from many individual particles with small pores between the particles to diffused particles with large pores in between large chunks of material. To model such a phenomenon, standard equations were scaled with unitless weighting functions to account for variable microstructures during heating. By weighting standard equations, the effects of microstructure could be more accurately described as a function of porosity and time.

A Single Probe Transient Moving Line Source Method for Determining Thermal Conductivity, Thermal Diffusivity, and Superficial Flow Velocity of a Porous Material With Flow

2011 ◽  
Author(s):  
Kevin D. Woods ◽  
Alfonso Ortega
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Analytical Solution ◽  
Porous Material ◽  
Flow Velocity ◽  
Empirical Data ◽  
Line Source ◽  
Single Probe ◽  
Moving Line Source ◽  
Moving Line

This paper presents a method to determine the effective thermal conductivity and thermal diffusivity of a porous material, as well as the superficial flow velocity of fluid flowing through the porous matrix using a single probe transient moving line source method. The method transforms the transient analytical solution for a moving line source using differentiation to produce three independent equations to solve for the three unknowns. Empirical data are presented from a laboratory scale test apparatus for three test cases with known properties and flow rates to validate the method. The method is then applied to field data from a standing column well used in ground source heat pump systems to obtain the thermal and flow properties of the ground formation. The properties are inserted into the transient analytical solution for a moving line source and superimposed over the empirical data showing agreement between the model and the data. The method is more accurate than traditional methods for estimating thermal properties when flow conditions are present, and the implementation of the method does not require any additional thermal data.

Percolation Effects on Electrical Resistivity and Electron Mobility

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
J. Weddell ◽  
A. Feinerman
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Aspect Ratio ◽  
Porous Material ◽  
Percolation Threshold ◽  
Electron Mobility ◽  
Past Research ◽  
Practical Applications ◽  
Percolation Thresholds ◽  
Theoretical Results

Percolation, defined as the study of transport across a porous material, can be used to determine transport quantities of a material such as electrical and thermal conductivity. Observing the way electrons flow across a porous conductive sheet is a common way that percolation studies are performed, and has many practical applications in electronics. This study determines how elliptical pores cut into a conductive sheet affect the percolation threshold; the remaining area of the conductive sheet when the current across it first becomes zero. Past research has been performed on this topic which yielded theoretical results of the percolation thresholds, and this study aims to verify those results experimentally. This study shows that as the aspect ratio of an ellipse approaches zero, the percolation threshold approaches one. This report also establishes a novel experimental method of studying percolating networks.

Heat Conduction of a Porous Material

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Koji Miyazaki ◽  
Saburo Tanaka ◽  
Daisuke Nagai
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Porous Material ◽  
Boundary Conditions ◽  
Periodic Boundary ◽  
Phonon Dispersion ◽  
Bulk Material ◽  
Periodic Boundary Conditions ◽  
Boltzmann Transport ◽  
Time Space

In this study, we introduce our numerical and experimental works for the thermal conductivity reduction by using a porous material. Recently thermal conductivity reduction has been one of the key technologies to enhance the figure of merit (ZT) of a thermoelectric material. We carry out numerical calculations of heat conduction in porous materials, such as phonon Boltzmann transport (BTE) and molecular dynamics (MD) simulations, in order to investigate the mechanism of the thermal conductivity reduction of a porous material. In the BTE, we applied the periodic boundary conditions with constant heat flux to calculate the effective thermal conductivity of porous materials.In the MD simulation, we calculated the phonon properties of Si by using the Stillinger–Weber potential at constant temperature with periodic boundary conditions in the x, y, and z directions. Phonon dispersion curves of single crystal of Si calculated from MD results by time-space 2D FFT are agreed well with reference data. Moreover, the effects of nanoporous structures on both the phonon group velocity and the phonon density of states (DOS) are discussed. At last, we made a porous p-type Bi2Te3 by nanoparticles prepared by a beads milling method. The thermal conductivity is one-fifth of that of a bulk material as well as keeping the same Seebeck coefficient as the bulk value. However, electrical conductivity was much reduced, and the ZT was only 0.048.

Numerical Simulation on the Effective Thermal Conductivity of Porous Material

2012 ◽  
Vol 557-559 ◽  
pp. 2388-2395
Author(s):  
Shan Qi Liu ◽  
Yong Bing Li ◽  
Xu Yao Liu ◽  
Bo Jing Zhu ◽  
Hui Quan Tian ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Porous Material ◽  
Effective Thermal Conductivity ◽  
Random Distribution ◽  
Simulation Method ◽  
Solid Skeleton ◽  
Material Models ◽  
Application Prospects ◽  
Good Agreement

The thermal conductivity of porous material is an important basic parameter, but it is not easy to study, due to the complexity of the structure of porous material. In the present work, we show a numerical simulation method to study the thermal conductivity of the porous material. We generate 200 material models with random distribution of solid skeleton and air for a fixed porosity, then we get the effective thermal conductivity of the porous material by Monte Carlo statistical analysis. The results are in good agreement with the previous empirical formula. The numerical results show that the effective thermal conductivity of porous material depends on the thermophysical properties of solid skeleton and air, the pore distribution and pore structure, the numerical error decreases with the increase in the number of grids, this finite element method can be used to estimate the effective thermal conductivity of composites and maybe has broad application prospects in terms of computing the effective thermal conductivity and other physical properties of composite material with known components.

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