Effective Thermal Conductivity of MoSi2/SiC Composites

2005 ◽  
Vol 492-493 ◽  
pp. 551-554
Author(s):  
Guang Zhao Bai ◽  
Wan Jiang ◽  
G. Wang ◽  
Li Dong Chen ◽  
X. Shi
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Effective Medium Theory ◽  
Thermal Conductance ◽  
Inclusion Size ◽  
Laser Flash ◽  
Flash Method ◽  
Medium Theory ◽  
Interfacial Thermal Conductance ◽  
Sic Composites

Thermal conductivity of as-prepared MoSi2/SiC composites has been determined by Laser Flash method. Interfacial thermal conductance for composites with 100nm SiC and with 0.5µm has been determined by using effective medium theory. The results of interfacial thermal conductance exhibit that both the inclusion size and the clustering of the inclusions play an important role in determining composite thermal conductivity.

On the Effective Thermal Conductivity of Nanofluids With Fractal Aggregation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
C. G. Subramaniam
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Effective Medium Theory ◽  
Functionally Graded ◽  
Fractal Aggregates ◽  
Medium Theory ◽  
Analytical Approximations ◽  
Proposed Model ◽  
Dispersing Medium ◽  
Dilute Limit

A generalized effective medium theory (EMT) is proposed to account for the fractal structure of the dispersed phase in a dispersing medium under the dilute limit. The thermal conductivity of nanofluids with fractal aggregates is studied using the proposed model. Fractal aggregates are considered as functionally graded spherical inclusions and its effective thermal conductivity is derived as a function of its fractal dimension. The results are studied for self-consistency and accuracy within the limitations of the analytical approximations used.

Temperature Dependency of the Effective Thermal Conductivity of Nickel Based Metal Foams

2006 ◽  
Author(s):  
Joerg Sauerhering ◽  
Oliver Reutter ◽  
Thomas Fend ◽  
Stefanie Angel ◽  
Robert Pitz-Paal
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Solid Phase ◽  
Total Porosity ◽  
Packed Bed ◽  
Laser Flash ◽  
Metal Foams ◽  
Flash Method ◽  
General Applicability ◽  
Hot Disk

This article presents experimental results of the thermal conductivity of sintered metal foams, which were manufactured by the Slip Reaction Foam Sintering (SRFS) process. For the determination of the thermal conductivity, the Transient Plane Source Technique, also known as Hot Disk, was employed. The thermal conductivity of cellular solids differs from that of their corresponding dense material. Therefore, the various pore size level effects contributing to the thermal conductivity are accounted for by introducing an effective thermal conductivity λeff. The thermal conductivity of the strut material, a sintered packed bed, was determined up to 700°C and compared to similar materials. The thermal diffusivity could also be determined by the Laser-Flash method and compared to the Hot Disk values. For the foams, λeff was determined for a total porosity of 0.85 up to 700°C. In this article, a dependency between the porosity and λeff can be shown. The linear rise of λeff up to 400°C can be due to the increase of the thermal conductivity of the solid phase. The measurements are validated by comparison of the received specific heat with values received by thermogravimetry measurements. The general applicability of the measurement method to heterogeneous materials such as metal foams is discussed and an outlook about further investigations is given.

scholarly journals Computational Assessment of Thermal Conductivity of Compacted Graphite Cast Iron

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Yue Wu ◽  
Jianping Li ◽  
Zhong Yang ◽  
Zhijun Ma ◽  
Yongchun Guo ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Conductance ◽  
Laser Flash ◽  
Flash Method ◽  
Compacted Graphite ◽  
Graphite Cast Iron ◽  
Calculation Results ◽  
The Difference ◽  
Metallographic Images ◽  
Experimental Values

Two-dimensional FE models of CGI with different pearlite contents for thermal conductivity analysis were established according to the real metallographic images obtained by Pro/E and ANSYS. Meanwhile, thermal conductivity of CGI with different pearlite contents was tested through the laser flash method. It is indicated that the thermal conductivity of CGI declines with the increase of pearlite. When pearlite is increased from 10% to 80%, the experimental values decline from 46.63 W/m·K to 36.86 W/m·K, reducing by 21%. However, this declining tendency becomes gentle and slight when pearlite is more than 40%. In addition, the calculation results with the consideration of interfacial contact thermal conductance (ICTC) and pearlite are much close to experimental values; especially when pearlite is 80%, the difference between them is only about 2%. It can be concluded that the FE models are convenient and reasonable to analyze thermal conductivity of CGI.

scholarly journals A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs Borophene

2021 ◽  
Author(s):  
Alessandro Di Pierro ◽  
Bohayra Mortazavi ◽  
Hamidreza Noori ◽  
Timon Rabczuk ◽  
Alberto Fina
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Content ◽  
Thermal Conductance ◽  
Single Layer ◽  
Interfacial Thermal Conductance ◽  
Aspect Ratios ◽  
The Matrix ◽  
Dynamics Simulations

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed a combined atomistic continuum multiscale modeling to explore the effective thermal conductivity of polymers nanocomposites made of PDMS polymer as the matrix and graphene and borophene as nanofillers. We first conduct classical molecular dynamics simulations to investigate the interfacial thermal conductance between graphene/PDMS and borophene/PDMS interfaces. Acquired results confirm that the interfacial thermal conductance between nanosheets and polymer increases from the single-layer to multilayered nanosheets and finally converges. The data provided by the atomistic simulations were then used in the finite element method simulations to evaluate the effective thermal conductivity of polymer nanocomposites at continuum level. We explore the effects of nanofillers type, their volume content, geometry aspect ratio and thickness on the nanocomposites effective thermal conductivity. As a very interesting finding, we show that borophene nanosheets, despite almost two orders of magnitude lower thermal conductivity than graphene, can yield very close enhancement in the effective thermal conductivity in comparison with graphene, particularly for low volume content and small aspect ratios and thicknesses. We conclude that for the polymer-based nanocomposites, significant improvement in the thermal conductivity can be reached by improving the bonding between the fillers and polymer or in another word enhancing the thermal conductance at the interface. By taking into account the high electrical conductivity of borophene, our results suggest borophene nanosheets as promising nanofillers to simultaneously enhance the polymers thermal and electrical conductivity.

Analysis of Heat Conduction in Dilute Nanofluids

2009 ◽  
Author(s):  
Le-Ping Zhou ◽  
Bu-Xuan Wang ◽  
Xiao-Ze Du ◽  
Yong-Ping Yang
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Steady State ◽  
Effective Thermal Conductivity ◽  
Effective Medium Theory ◽  
Constant Heat Flux ◽  
Brownian Diffusion ◽  
Uniform Temperature ◽  
Medium Theory ◽  
Basic Fluid

In this paper, we assume that a nanofluid is a mixture consisting of a continuous base fluid component and a discontinuous nanoparticle component. Then, based on the analysis of Buongiorno in 2006 for critical slip mechanisms in nanofluids, we consider the effects of Brownian diffusion and thermophoresis of nanoparticles on heat and mass flux in nanofluid. With the coupled conservation equations, we analyze the heat conduction properties of general nanofluids under three conditions: 1) stationary fluid with uniform temperature, 2) stationary fluid under constant temperature boundary, and 3) stationary fluid under constant heat flux boundary. The results show that nanofluid effective thermal conductivity depends on the thermal conductivity of nanoparticle and basic fluid, particle concentration, particle size, particle distribution, Brownian and thermal diffusion, boundary condition and time. It indicates that the nanofluid effective thermal conductivity can be well predicted for stationary fluid with uniform temperature from classical effective medium theory such as Maxwell’s approach. However, the measurements applying steady or unsteady heat conduction methods for pure materials fail to predict correctively the effective thermal conductivity of nanofluid and are influenced by boundary conditions. Preliminary conclusions include approximate correlations of effective thermal conductivity of dilute nanofluids using steady state and quasi-steady state measuring methods.

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