The thermal conductivity of granular and weakly sintered materials

Dul'nev, G. N.; Zarichnyak, Yu. P.; Muratova, B. L.

doi:10.1007/bf00828631

“…λ p is a prediction from the popular Lichtenecker model, which is a weighted average geometric mean model called "logarithmic mixing rule." 45 The parameters are assumed in calculation: the BN density is 2.29 g/cm 3 ; the PE density is 0.95 g/cm 3 ; the λ PE is 0.39 W/m K; the λ BN∥ is 600 W/m K; and the λ BN⊥ is 15 W/m K. 46,47 Figure 5d plots the calculated λ p∥ , λ p⊥ , and λ p as a function of ϕ BN . The experimental λ ∥ and λ ⊥ for all PE/BN films fall between the highest λ p∥ and the lowest λ p⊥ .…”

Section: Thermal Conductivitymentioning

confidence: 99%

High-Speed Melt Stretching Enables Facile Fabrication of Mechanically Superstrong and Highly Thermo-Conductive Anisotropic Polyethylene/BN Nanocomposite Films

Sun,

Ye,

Huang

et al. 2024

ACS Appl. Polym. Mater.

0

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Fabrication of high-performance thermally conductive polymer nanocomposites through melt processing is crucial for large-scale industrial applications. However, this remains underdeveloped due to challenges with regulating nanofillers in viscous polymer melts. Herein, we propose a high-speed melt stretching strategy to prepare thermally conductive nanocomposite films of high-density polyethylene/boron nitride (PE/BN). By rapidly applying a maximum 80× stretch ratio to the high-temperature composite melt using a homemade two-drum extensional machine, two-dimensional BN nanosheets are highly oriented and redispersed within the PE matrix. This enables the production of nanocomposite films with superstrong mechanical properties, including high strength (>90 MPa) and modulus (>3 GPa). The horizontally aligned BN nanosheets simultaneously create fast pathways for phonon transport, resulting in a high in-plane thermal conductivity of 6.56 W/m K for the film with 40 wt % BN. This value is superior to previous reports on polymer/BN composites with similar filler fractions and ensures an excellent cooling capability of the film for commercial LED modules. Additionally, the melt-stretched PE/BN films demonstrate significantly improved thermo-mechanical and electrical insulating properties compared to their hot-pressed counterparts, attributed to the microstructural advantages. This work offers a viable melt processing approach for developing high-performance general plastic-based thermally conductive films toward electronic device applications.

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“…1. Dul'nev< 22 ) showed that the packing density is not only affected by the presence of the wall, but also by the geometry of neighboring spheres. This effect occurs in both the longitudinal and radial direction.…”

Section: Ll Thermal Conductivity Of Unrestructured Bedsmentioning

confidence: 99%

Effective thermal conductivity in multi-fraction reactor fuels.

Peterson

¹

,

Fletcher

²

,

Peddicord

³

1987

J. Nucl. Sci. Technol.

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The effective thermal conductivity of the fuel elements used in nuclear reactors is of significant importance in determining the performance, reliability and operational efficiency of the reactors. This is especially true in sphere-pac reactor fuels, in which the fuel elements are comprised of packed beds of spherical or near spherical particles.Presented here is a review of the analytical and experimental investigations, conducted to predict or determine the thermal conductivity of beds of packed spherical particles such as those found in sphere-pac reactor fuels. Included are packed beds in which the particles are all of uniform size and beds in which several different sizes exist. Analytical techniques for packed beds both with and without restructuring are presented, discussed and compared with the existing experimental data.Based upon this review, it is apparent that additional analytical and experimental investigations are necessary in order to accurately predict the effective thermal conductivity in sphere-pac reactor fuels. Specific areas where this need is greatest are identified and discussed.

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“…As noted by Dul'nev et al < 22 ), this com· parison is not always sufficiently extensive to cover the entire range of parameters and it is therefore often necessary to evaluate a given model with respect to specific applications. In doing this for the aforementioned work, it is apparent that although in a number of cases the predictions agree quite well with the existing experimental data, the models cannot be directly transferred to sphere-pac reactor fuels for several reasons.…”

Section: Unrestructured Bedsmentioning

confidence: 99%

Effective Thermal Conductivity in Multi-Fraction Reactor Fuels

Peterson

¹

,

Fletcher

²

,

Peddicord

³

1987

Journal of Nuclear Science and Technology

1

0

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The effective thermal conductivity of the fuel elements used in nuclear reactors is of significant importance in determining the performance, reliability and operational efficiency of the reactors. This is especially true in sphere-pac reactor fuels, in which the fuel elements are comprised of packed beds of spherical or near spherical particles.Presented here is a review of the analytical and experimental investigations, conducted to predict or determine the thermal conductivity of beds of packed spherical particles such as those found in sphere-pac reactor fuels. Included are packed beds in which the particles are all of uniform size and beds in which several different sizes exist. Analytical techniques for packed beds both with and without restructuring are presented, discussed and compared with the existing experimental data.Based upon this review, it is apparent that additional analytical and experimental investigations are necessary in order to accurately predict the effective thermal conductivity in sphere-pac reactor fuels. Specific areas where this need is greatest are identified and discussed.

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The thermal conductivity of granular and weakly sintered materials

Cited by 5 publications

References 7 publications

High-Speed Melt Stretching Enables Facile Fabrication of Mechanically Superstrong and Highly Thermo-Conductive Anisotropic Polyethylene/BN Nanocomposite Films

High-Speed Melt Stretching Enables Facile Fabrication of Mechanically Superstrong and Highly Thermo-Conductive Anisotropic Polyethylene/BN Nanocomposite Films

Effective thermal conductivity in multi-fraction reactor fuels.

Effective Thermal Conductivity in Multi-Fraction Reactor Fuels

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