Thermal Conductivity and Thermal Diffusivity

1983 ◽  
pp. 133-161
Author(s):  
J. G. Hust
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Diffusivity ◽  
Heat Transport ◽  
Measurement Methods ◽  
Basic Principles ◽  
Qualitative And Quantitative ◽  
Effects Of Temperature ◽  
Theoretical Results

Abstract This chapter presents basic principles and the theoretical results of heat transport in solids. Thermal conductivity and thermal diffusivity are the principal properties discussed. Discussions are also included on the effects of temperature, magnetic field, and metallurgical variations caused by composition, processing, and heat-treatment differences. Numerous graphs illustrate the qualitative and quantitative effects of these variables. Measurement methods and associated accuracies and pertinent empirical correlations are presented.

Anomalous Heat Conduction, Diffusion and Heat Rectification in Nanoscale Structures

2009 ◽  
Author(s):  
Gang Zhang ◽  
Nuo Yang ◽  
Gang Wu ◽  
Baowen Li
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Heat Transport ◽  
Nano Materials ◽  
Fourier Law ◽  
Nanoscale Structures ◽  
Recent Developments ◽  
Theoretical Results ◽  
Good Agreement ◽  
Anomalous Heat

In this paper, we report the recent developments in the study of heat transport in nano materials. First of all, we show that phonon transports in nanotube super-diffusively which leads to a length dependence thermal conductivity, thus breaks down the Fourier law. Then we discuss how the introduction of isotope doping can reduce the thermal conductivity efficiently. The theoretical results are in good agreement with experimental ones. Finally, we will demonstrate that nanoscale structures are promising candidates for heat rectification.

The Influence of Heat Treatment Parameters on the Thermal Diffusivity of WE54 and Elektron 21 Magnesium Alloys

2011 ◽  
Vol 312-315 ◽  
pp. 489-494 ◽  
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń ◽  
Grzegorz Moskal
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Solid Solution ◽  
Thermal Diffusivity ◽  
Magnesium Alloys ◽  
Solute Element ◽  
Strengthening Phases

In the present study, the thermal diffusivity and conductivity of WE54 and Elektron 21 alloys were studied. The results showed the thermal diffusivity of WE54 and Elektron 21 alloys were temperature and microstructure dependent. The thermal diffusivity of both alloys was dependent on the content of the solute element in the α-Mg matrix. The solid solution of Y and Gd in Mg has a lower thermal conductivity than alloys where the intermetallic Mg3(Nd,Gd) and Mg14Y2Nd phases are present. The formation of strengthening phases during ageing caused the consumption of the solute element in the α -Mg matrix, and improved the thermal conductivity of the alloys.

Thermal Properties of Microcrystalline Cellulose Derived Carbons

2007 ◽  
Author(s):  
Yo-Rhin Rhim ◽  
Dajie Zhang ◽  
Dennis C. Nagle ◽  
Michael Rooney ◽  
Cila Herman
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Microcrystalline Cellulose ◽  
Heat Treatment Temperature ◽  
Structural Characteristics ◽  
Treatment Temperature ◽  
Carbon Clusters ◽  
Flash Method

The thermal transport properties were studied for carbons produced by the carbonization of microcrystalline cellulose. Thermal diffusivity, specific heat, and thermal conductivity were measured via flash method for cellulose derived carbons prepared at various heat treatment temperatures ranging from 250°C to 1000°C. The thermal diffusivity as a function of increasing heat treatment temperature was observed to have four distinct linear regions, which could be related directly to the microstructures of the materials generated by the specific heat treatment temperature. Specific heat values indicated the coexistence of polar and non-polar phases in both partially carbonized materials obtained at lower heat treatment temperatures and fully carbonized materials formed at higher heat treatment temperatures. For partially carbonized materials, the polar groups consisting of residual hydroxyl and carboxyl were still present. For fully carbonized materials, the polar phases have largely been volatilized and conductive nano-carbon clusters were nucleated and observed to grow in an amorphous carbon bed until percolation effects were observed. Such structural characteristics are well supported by FT-IR characterizations. Lastly, a linear relationship between testing temperature and thermal conductivity indicates boundary scattering between highly conductive carbon clusters as the main mechanism for heat conduction.

On the cross-field flux of heat in a magnetoplasma

1983 ◽  
Vol 29 (1) ◽  
pp. 143-154 ◽  
Author(s):  
L. C. Woods
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Heat Transport ◽  
Strong Magnetic Field ◽  
Electron Gas ◽  
Axial Current ◽  
Plasma Pressure ◽  
Equivalent Thermal Conductivity ◽  
Cylindrical Plasma ◽  
The Cross

A new theory is developed for the transport of energy across a strong magnetic field. The mechanism is micro-convection by sheared fluid elements, and it proves to be much more effective in heat transport than classical conduction. The equivalent thermal conductivity is calculated for the electron gas in a cylindrical plasma carrying an axial current. When the plasma pressure can be neglected, this conductivity is about 400 times greater than the classical value under certain typical conditions.

Über die Verschiebung zylindrischer Lichtbögen ohne Materiebewegung

1968 ◽  
Vol 23 (3) ◽  
pp. 424-432
Author(s):  
Jürgen Raeder
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Steady State ◽  
Gas Flow ◽  
Space Variable ◽  
Electric Arc ◽  
Explicit Dependence ◽  
Heating And Cooling ◽  
Theoretical Results ◽  
Good Agreement

An electric arc may be displaced by a magnetic field, by a gas flow and also by unsymmetric heating and cooling. This occurs for instance, if a portion of the wall of a wall-stabilized arc is heated. For this case the displacement is investigated theoretically for steady state conditions. Furthermore the deflection is calculated for an explicit dependence of electrical and thermal conductivity upon a space variable. The different possibilities considered in theory are realized experimentally. The measurements are in good agreement with the theoretical results.

scholarly journals Processing and Generalization of Experimental Data on Thermal Diffusivity and Thermal Conductivity of Magnetic Fluids Depending on the Impact of the Magnetic Field

2021 ◽  
Vol 27 (2) ◽  
pp. 231-237
Author(s):  
D. S. Dzhuraev
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Iron Powder ◽  
Experimental Studies ◽  
Magnetic Fluids ◽  
Transformer Oil ◽  
The Impact ◽  
The Magnetic Field

The paper presents the results of experimental studies of the thermal diffusivity and thermal conductivity of magnetic fluids based on transformer oil, depending on the effect of a magnetic field in the range of B = 1.59...3.866 mT, and the addition of iron powder 0.1...0.3 g with an interval of 0.05 g. Equations were obtained for calculation with a certain fraction of error in thermal diffusivity and thermal conductivity of unexplored magnetic fluids.

scholarly journals Тепловые и магнитокалорические свойства манганитов La-=SUB=-0.7-=/SUB=-Sr-=SUB=-0.3-x-=/SUB=-Ba-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-

2021 ◽  
Vol 63 (12) ◽  
pp. 2028
Author(s):  
А.Б. Гаджиев ◽  
А.Г. Гамзатов ◽  
А.Б. Батдалов ◽  
З.А. Хуршилова ◽  
А.М. Алиев
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Crystal Lattice ◽  
Spin Fluctuations ◽  
Partial Substitution ◽  
Substitution Level ◽  
Magnetocaloric Properties ◽  
Disorder Parameter ◽  
Local Distortions

The results of a study of the effect of partial substitution of Sr2+ ions by Ba2+ ions on the thermophysical and magnetocaloric properties of manganite La0.7Sr0.3-xBaxMnO3 (x = 0; 0.02; 0.05 and 0.10) in the temperature range 100-400 K and in a magnetic field up to 1.8 T. It is shown that such a substitution leads to a significant decrease in TC. In the behaviour of the thermal diffusivity (T) and thermal conductivity (T) near TС, minima were found that are associated with both the scattering of phonons by local distortions of the crystal lattice and by spin fluctuations. The absolute values of thermal conductivity decrease with an increase in the disorder parameter. The magnetocaloric effect exhibits a weak dependence on the substitution level (x).

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