19-Fold thermal conductivity increase of carbon nanotube bundles toward high-end thermal design applications

This study examines the thermal conductivity of some selected soil samples from coastal sandlandform inIlaje local government area of Ondo State, Nigeria. The soil samples were sieved into different particle sizes; 300 , 425 , 600 , 850 , and 1180 Â with appropriate mesh and moulded in form of a Leeâ€™s disc. The thermal conductivity of the samples was determined using parallel plate method. The value of the thermal conductivity increase as the moisture content increaseand decrease with increase in particle sizes for the soil samples. The values of the thermal conductivity obtainedÂ Â rangedbetween 0.3444 Â and1.8894 . It was noted that the conductivity of the landforms conforms to the range of conductivities of soil required for some specific crops such as maize, cowpea, pineapple, okro and root crops. The results in the research would be useful to soil/building and soil scientists as well as modern mechanized farmers in determined Â appropriate land forms for agricultural and structural purposes.

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Thermal Conductivity and Specific Heat Capacity of Carbon Nanotube Bundles

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 2 ◽

10.1115/ht2007-32487 ◽

2007 ◽

Author(s):

John Shelton ◽

Frank Pyrtle

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotubes ◽

Heat Capacity ◽

Carbon Nanotube ◽

Specific Heat ◽

Specific Heat Capacity ◽

Element Analysis ◽

Single Walled Carbon ◽

Nanotube Bundles ◽

Dynamics Simulations

Carbon nanotubes (CNTs) have been thoroughly documented to demonstrate superior heat transfer properties. It has also been determined that these properties decrease substantially as overall dimensions increase from the nanoscale to the microscale. Using non-equilibrium molecular dynamics simulations and finite element analysis, the influence of both internal and external thermal boundary resistance effects on the thermal conductivity and specific heat capacity of single walled carbon nanotube bundles were investigated. Comparisons were made between accepted property values for single CNTs and for CNT bundles. Also, energy transfer between varying sized bundles of single-walled carbon nanotubes (SWCNTs) and a surrounding pressure-driven Lennard-Jones (LJ) fluid were calculated.

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Thermophysical Properties and Pool Boiling Characteristics of Water in Polyalphaolefin Nanoemulsion Fluids

ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2012-75232 ◽

2012 ◽

Cited By ~ 4

Author(s):

Jiajun Xu ◽

Bao Yang

Keyword(s):

Thermal Conductivity ◽

Thermophysical Properties ◽

Dynamic Viscosity ◽

Self Assembly ◽

Pool Boiling ◽

Water Concentration ◽

Interesting Phenomenon ◽

Conductivity Increase ◽

Thermal Conductivity Increase ◽

Measured Thermal Conductivity

In this work, thermophysical properties and pool boiling characteristics of water-in-polyalphaolefin (PAO) nanoemulsion fluids and their dependence on water concentration have been investigated experimentally. Water-in-PAO nanoemulsion fluids are formed via self-assembly with surfactant sodium sullfosuccinate (AOT). Thermal conductivity of the fluids is found to increase with water concentration, as expected from the Maxwell equation. However, the measured thermal conductivity increase is very moderate, e.g., a 16% increase for 8.6Vol. %. Unlike thermal conductivity, the dynamic viscosity of these nanoemulsion fluids first increases with water concentration, reaches a maximum, and then decreases. This trend could be attributed to the attractive forces among water droplets. The boiling behavior of these nanoemulsion fluids has been altered due to water nanodroplets. Adding water nanodroplets can lower the nanoemulsion’s boiling point compared to the pure PAO. Another interesting phenomenon observed is that pool boiling of nanoemulsion fluids randomly follows two different curves when the water concentration is in the range of 5.3 Vol. % to 7.8 Vol. %. The mechanism underlying this phenomenon is not understood yet, but it may be related to the evolution of microstructures in the water-in-PAO nanoemulsion fluids.

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Study on Thermal Conductivities of Composite Adsorbents for Adsorption Refrigeration

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.556-562.232 ◽

2014 ◽

Vol 556-562 ◽

pp. 232-235

Author(s):

Yan Lin ◽

Jiao Gao

Keyword(s):

Thermal Conductivity ◽

Aqueous Solution ◽

Coupling Effect ◽

Mass Ratio ◽

Adsorption Refrigeration ◽

Composite Adsorbents ◽

Conductivity Increase ◽

Thermal Conductivity Increase ◽

Thermal Conductivities

Twenty-four Cacl2/ENG molded composite adsorbents specimen were successfully prepared by aqueous solution and squeezing method. The thermal conductivities of the samples were tested by nanoflash LFA447. The experiment results show that: the thermal conductivity perpendicular to the direction of compression is over 1.2 times higher than that parallel to the direction of compression, which prove that the thermal conductivity is anisotropic. Within a certain range, the thermal conductivity is enhanced with increasing density and decreasing mass ratio. Under mass ratio is 2:1 and density rise from 600 kg/m3 to 700 kg/m3, thermal conductivity increase fastest. Density and mass ratio has coupling effect on the thermal conductivity of Cacl2/ENG molded composite adsorbents.

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Thermal Conductivity and Thermal Expansion Properties of AlN/EP Composite

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.482-484.1410 ◽

2012 ◽

Vol 482-484 ◽

pp. 1410-1413 ◽

Cited By ~ 1

Author(s):

Zhen Hui Ma ◽

Jin Liang Huang ◽

Yong Jun Gu ◽

Biao Jin ◽

Guan Yu Chen

Keyword(s):

Thermal Conductivity ◽

Thermal Expansion ◽

Epoxy Matrix ◽

Volume Fraction ◽

Coefficient Of Thermal Expansion ◽

Casting Method ◽

Conductivity Increase ◽

Thermal Conductivity Increase ◽

Properties Of Composites

AlN/epoxy (AlN/EP) composites were fabricated by casting method. The effects of the AlN content on microstructure, thermal conductivity and thermal expansion properties of composites were investigated. The results indicate that with the AlN content increasing, the thermal conductivity increase, while the coefficient of thermal expansion (CTE) decreases. When the volume fraction of AlN is 25%, the thermal conductivity is 0.507 W/m•K, which is about 2.5 times higher than that of the epoxy matrix, while the coefficient of thermal expansion is 53.7 ppm/°C. The thermal conductivity results obtained were also analyzed using the Maxwell-Eucken model to explain the effect of AlN fillers on the formation of thermal conductive networks.

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Effects of Nanofilled Particle Forms and Dispersion Modes on Properties of Carbon-Based Energy Storage Composites

Advances in Polymer Technology ◽

10.1155/2020/6865497 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Jia Yu ◽

Hui Li ◽

Li Kong ◽

Hongji Zhu ◽

Qingshan Zhu ◽

...

Keyword(s):

Thermal Conductivity ◽

Energy Storage ◽

Mass Fraction ◽

Phase Change Materials ◽

Thermal Control ◽

Enhancement Effect ◽

Conductivity Enhancement ◽

Conductivity Increase ◽

Thermal Conductivity Increase ◽

Carbon Based

How to improve the thermal conductivity of phase change materials (PCMs) is always the key to thermal control technology. At present, the thermal conductivity of PCMs has two ways to improve: one is to fill the matrix with high thermal conductivity and the other is to fill nanoparticles. After combining the two methods, the choice of filled nano-SiO2, carbon nanotubes (CNTs), or graphene (GNPs) has different effects on the performance of carbon-based energy storage composites. Filling paraffin with foamed carbon increased the thermal conductivity of pure paraffin from 0.25 W/(m·K) to 8.3083 W/(m·K), an increase of 33.2 times. When the nanoparticle mass fraction is 5%, the enthalpy of GNP composites is 10 J·g-1 less than that of SiO2 composites. Under the same mass fraction, compared with the thermal conductivity enhancement effect of SiO2 composites, the thermal conductivity increase effects of CNTs and GNP composites are 6.7 and 15.8 times the thermal conductivity increase of SiO2 composites, respectively. The comparison of theoretical and experimental values shows that different nanoparticle forms and dispersion modes have different effects on the performance of carbon-based energy storage composites, among which GNPs have the greatest improvement in the thermal conductivity of carbon-based composites.

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Improvement of the Thermoelectric Properties of the Chimney–Ladder Compounds in the Ru-Mn-Si System

MRS Proceedings ◽

10.1557/proc-1218-z06-09 ◽

2009 ◽

Vol 1218 ◽

Cited By ~ 1

Author(s):

Norihiko L. Okamoto ◽

Yutaka Hashimoto ◽

Tatsuya Koyama ◽

Hiroki Adachi ◽

Kyosuke Kishida ◽

...

Keyword(s):

Thermal Conductivity ◽

Heat Treatment ◽

Thermoelectric Properties ◽

Growth Direction ◽

Compositional Variation ◽

Nominal Composition ◽

Directionally Solidified ◽

Conductivity Increase ◽

Thermal Conductivity Increase ◽

Metal Sublattice

AbstractDirectionally solidified alloys in the Ru-Mn-Si system exhibit a particular microstructure including columnar compositional variation due to the formation of many different chimney-ladder phases along the growth direction. Despite the existence of the compositional variation, the crystal orientations of the neighboring chimney-ladder phases are preserved. Over the compositional interfaces, the metal sublattice is considered to be continuous while the Si sublattice is not. Heat treatment of the directionally solidified alloy with the nominal composition of Ru0.10Mn0.90Si1.732 at 1100°C coarsens the compositional domains so as to reduce the density of the compositional interfaces. The values of the thermal conductivity increase with the decrease in the density of the compositional interfaces whereas those of the Seebeck coefficient and electrical resistivity are almost unchanged after the heat treatment. It is considered that the thermoelectric properties of the chimney-ladder compounds in the Ru-Mn-Si system can be enhanced by introducing a high density of the compositional interfaces.

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