THERMAL CONDUCTIVITY OF METALS AT HIGH TEMPERATURES: I. DESCRIPTION OF THE APPARATUS AND MEASUREMENTS ON IRON

1947 ◽  
Vol 25a (6) ◽  
pp. 357-374 ◽  
Author(s):  
L. D. Armstrong ◽  
T. M. Dauphinee
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Temperatures ◽  
Armco Iron ◽  
Absolute Error ◽  
Cylindrical Sample ◽  
Comprehensive Analysis ◽  
Temperature Curve ◽  
Temperature Range ◽  
Thermal Conductivities

An apparatus for measuring the thermal conductivity of metals in the temperature range 0° to 800 °C. is described. The method utilizes unidirectional heat flow in a cylindrical sample in a vacuum. The advantages of the method are outlined and a comprehensive analysis of possible errors in the measurements is included. Measurements on Armco iron indicate that results with an absolute error of less than 2% may be obtained. The results of measurements on a sample of Armco iron gave thermal conductivities of 0.1819 c.g.s units at 0 °C. and 0.0698 c.g.s. units at 800 °C. A change in slope of the thermal conductivity–temperature curve was found at a temperature of approximately 375 °C., and is tentatively attributed to the presence of 0.03% nickel impurity.

scholarly journals The variation with temperature of the thermal con­ductivity and the X-ray structure of some micas I—The thermal conductivity up to 600° C

1937 ◽  
Vol 163 (913) ◽  
pp. 189-198 ◽  
Keyword(s):  
Thermal Conductivity ◽  
High Temperatures ◽  
Temperature Curve ◽  
X Ray ◽  
Temperature Range ◽  
Conductivity Change ◽  
Initial Values ◽  
Thermal Conductivities

The authors recently had occasion to measure the thermal conductivities of several varieties of mica up to a temperature of 600° C. In the course of this work it has been observed that whereas the thermal conductivities of the muscovite varieties of mica alter but little over this temperature range, the thermal conductivities of certain phlogopite micas decrease to about one-third of their initial values when the micas are heated to about 200° C. In such cases there is incomplete reversibility in the thermal conductivity temperature curve on cooling. Subsequent examination of these micas by means of X-ray crystal analysis has revealed the fact that in those samples which suffered appre­ciable change in conductivity, the arrangement of the elementary crystals composing the mica laminae becomes displaced from their ordered setting at approximately the same temperature as the thermal conductivity change. The present paper describes the thermal conductivity experiments, which are believed to be the first determinations carried out on mica to high temperatures. In the paper which follows, Mr. W. A. Wood describes the X-ray experiments on some of these samples of mica.

Effects of Nb doping on thermoelectric properties of Zn4Sb3 at high temperatures

2009 ◽  
Vol 24 (2) ◽  
pp. 430-435 ◽  
Author(s):  
D. Li ◽  
H.H. Hng ◽  
J. Ma ◽  
X.Y. Qin
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
High Temperatures ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Performance ◽  
Temperature Range ◽  
A Value ◽  
Nb Doping ◽  
Thermal Conductivities

The thermoelectric properties of Nb-doped Zn4Sb3 compounds, (Zn1–xNbx)4Sb3 (x = 0, 0.005, and 0.01), were investigated at temperatures ranging from 300 to 685 K. The results showed that by substituting Zn with Nb, the thermal conductivities of all the Nb-doped compounds were lower than that of the pristine β-Zn4Sb3. Among the compounds studied, the lightly substituted (Zn0.995Nb0.005)4Sb3 compound exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity. Its figure of merit, ZT, was greater than the undoped Zn4Sb3 compound for the temperature range investigated. In particular, the ZT of (Zn0.995Nb0.005)4Sb3 reached a value of 1.1 at 680 K, which was 69% greater than that of the undoped Zn4Sb3 obtained in this study.

ON MEASUREMENT OF THERMAL CONDUCTIVITY AT HIGH TEMPERATURES

1961 ◽  
Vol 39 (7) ◽  
pp. 1029-1039 ◽  
Author(s):  
M. J. Laubitz
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Temperatures ◽  
Mathematical Analysis ◽  
Temperature Range ◽  
Linear Heat ◽  
Flow Systems

A method is given for exact mathematical analysis of linear heat flow systems used in measuring thermal conductivity at high temperatures. It is shown that a popular version of such a system is very sensitive to the alignment of its components, which seriously limits the temperature range of its satisfactory use.

scholarly journals The thermal conductivities of certain approximately pure metals and alloys at high temperatures

1931 ◽  
Vol 134 (823) ◽  
pp. 57-76 ◽  
Keyword(s):  
Heat Flow ◽  
High Temperatures ◽  
Heat Losses ◽  
Metals And Alloys ◽  
Maximum Temperature ◽  
Internal Heating ◽  
Heating Coil ◽  
Pure Metals ◽  
Guard Tube ◽  
Thermal Conductivities

Measurements have been made by several observers on the thermal conductivities of metals and alloys up to high temperatures. Heat losses to the surroundings become large at high temperatures, hence the guard tube method, which to a great extent eliminates these losses, has been popular for work at these temperatures. This method was described and used by Berget in 1888, and later by Wilkes. These observers measured the rate of heat flow by a calorimetric method, which is not suitable for work at high temperatures. Honda and Simidu, using an internal heating coil, determined the heat flow from the energy input and were able to obtain results for nickel and steel to over 800°C. More recently, Schofield, using the guard tube method with an internal heating coil, has obtained results up to a maximum temperature of 700°C. with five metals. The present work was undertaken with a view to continuing the work of Professor C. H. Lees on the effect of temperatures between —160°C. and 15°C. on the thermal conductivities of nine metals and six alloys.

Thermal Expansion and Isotopic Composition Effects on Lattice Thermal Conductivities of Crystalline Silicon

2006 ◽  
Author(s):  
Yunfei Chen ◽  
Guodong Wang ◽  
Deyu Li ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Md Simulation ◽  
Lattice Thermal Conductivity ◽  
Mass Difference ◽  
Dynamics Simulation ◽  
Temperature Range ◽  
Simulation Results ◽  
Callaway Model ◽  
Thermal Conductivities

Equilibrium molecular dynamics simulation is used to calculate lattice thermal conductivities of crystal silicon in the temperature range from 400K to 1600K. Simulation results confirmed that thermal expansion, which resulted in the increase of the lattice parameter, caused the decrease of the lattice thermal conductivity. The simulated results proved that thermal expansion imposed another type resistance on phonon transport in crystal materials. Isotopic and vacancy effects on lattice thermal conductivity are also investigated and compared with the prediction from the modified Debye Callaway model. It is demonstrated in the MD simulation results that the isotopic effect on lattice thermal conductivity is little in the temperature range from 400K to 1600K for isotopic concentration below 1%, which implies the isotopic scattering on phonon due to mass difference can be neglected over the room temperature. The remove of atoms from the crystal matrix caused mass difference and elastic strain between the void and the neighbor atoms, which resulted in vacancy scattering on phonons. Simulation results demonstrated this mechanism is stronger than that caused by isotopic scattering on phonons due to mass difference. A good agreement is obtained between the MD simulation results of silicon crystal with vacancy defects and the data predicted from the modified Debye Callaway model. This conclusion is helpful to demonstrate the validity of Klemens' Rayleigh model for impurity scattering on phonons.

scholarly journals Determination of the anisotropic thermal conductivity of an aerogel-based plaster using transient plane source method

2021 ◽  
Vol 2069 (1) ◽  
pp. 012030
Author(s):  
A N Karim ◽  
B Adl-Zarrabi ◽  
P Johansson ◽  
A Sasic Kalagasidis
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Performance ◽  
Plane Source ◽  
Weak Anisotropy ◽  
Source Method ◽  
Transient Plane Source ◽  
Anisotropic Thermal Conductivity ◽  
Transient Plane Source Method ◽  
Thermal Conductivities

Abstract Aerogel-based plasters are composite materials with declared thermal conductivities in the range of traditional insulating materials, i.e. 30-50 mW/(m·K). Based on the results from reported field measurements, aerogel-based plasters can significantly reduce the thermal transmittance of uninsulated walls. However, the in-situ measured thermal conductivities have sometimes been higher than the declared values measured in laboratory and in the main direction of the heat flow. Meanwhile, the anisotropic thermal performance of aerogel-based plasters, i.e., deviating thermal performance in the different directions of heat flow, has not been explored yet. The objective of this study is thus to evaluate the anisotropic thermal conductivity of an aerogel-based plaster. This is done in a set of laboratory measurements using the transient plane source method. Six identical and cubic samples with the dimensions of 10×10×10 cm3 were paired two and two, creating three identical sample sets. In total, 360 measurements of thermal conductivity and thermal diffusivity, and 130 measurements for specific heat capacity were conducted. The results indicate a weak anisotropy of less than ±6.5 % between the three directions (x, y, z). Considering the accuracy of the selected measurement technique, better than ±5 %, supplementary measurements using another technique are recommended.

Anisotropy of thermal conductance in near-ideal graphite

1965 ◽  
Vol 284 (1396) ◽  
pp. 17-31 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Basal Plane ◽  
Thermal Conduction ◽  
Theoretical Estimate ◽  
Thermal Conductance ◽  
Temperature Range ◽  
Neutron Damage ◽  
Plane Direction ◽  
Umklapp Scattering ◽  
Thermal Conductivities

Measurements of thermal conductivities of a number of pyrolytic graphites are reported in­cluding values for annealed, hot pressed graphite (IFPA 57). Thermal conductivities of IFPA 57 in both basal plane and c -axis directions approach the values for ideal graphite at higher tem­peratures. A theoretical estimate of the anisotropy of thermal conduction in ideal graphite in the temperature range where umklapp scattering predominates shows fair agreement with the present experimental value. Such defects as are normally present in well-oriented graphite produce comparatively little effect on the c -axis thermal conductivity and exposure to neutron damage has a much smaller effect in the direction of the c axis, than in the basal plane direction.

An Experimental Evaluation of the Effective Thermal Conductivities of Packed Beds at High Temperatures

1994 ◽  
Vol 116 (4) ◽  
pp. 829-837 ◽  
Author(s):  
K. Nasr ◽  
R. Viskanta ◽  
S. Ramadhyani
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
High Temperatures ◽  
Radiation Heat Transfer ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Packed Beds ◽  
Packing Materials ◽  
Bed Temperature ◽  
Thermal Conductivities

Combined conduction and radiation heat transfer in packed beds of spherical particles was investigated. Three different packing materials (alumina, aluminum, and glass) of various particle diameters (2.5 to 13.5 mm) were tested. Internal bed temperature profiles and corresponding effective thermal conductivities were measured under steady-state conditions for a temperature range between 350 K and 1300 K. The effects of particle diameter and local bed temperature were examined. It was found that higher effective thermal conductivities were obtained with larger particles and higher thermal conductivity packing materials. The measured values for the effective thermal conductivity were compared against the predictions of two commonly used models, the Kunii–Smith and the Zehner–Bauer–Schlu¨nder models. Both models performed well at high temperatures but were found to overpredict the effective thermal conductivity at low temperatures. An attempt was made to quantify the relative contributions of conduction and radiation. Applying the diffusion approximation, the radiative conductivity was formulated, normalized, and compared with the findings of other investigators.

scholarly journals THERMAL CONDUCTIVITY OF URANIUM DIOXIDE AND ARMCO IRON BY AN IMPROVED RADIAL HEAT FLOW TECHNIQUE

1964 ◽  
Author(s):  
T.G. Godfrey ◽  
W. Fulkerson ◽  
T.G. Kollie ◽  
J.P. Moore ◽  
D.L. McElroy
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Uranium Dioxide ◽  
Armco Iron ◽  
Radial Heat Flow ◽  
Radial Heat

THERMAL AND ELECTRICAL PROPERTIES OF ARMCO IRON AT HIGH TEMPERATURES

1960 ◽  
Vol 38 (7) ◽  
pp. 887-907 ◽  
Author(s):  
M. J. Laubitz
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Electrical Properties ◽  
High Temperatures ◽  
Curie Point ◽  
Armco Iron ◽  
Discontinuous Change ◽  
Thermal And Electrical Properties

Thermal and electrical conductivity, thermoelectric power vs. platinum, and thermal expansion of Armco iron were determined in the temperature range of 0 °C to 1000 °C. All these properties show a discontinuous change at the α–γ transition of iron, and a change in slope at the Curie point. These measurements were carried out as a contribution to a co-operative determination of thermal conductivity of Armco iron at high temperatures.

Sign in / Sign up

Export Citation Format

Share Document