The thermal conductivities of some dielectric solids at low temperatures (Experimental)

1951 ◽  
Vol 208 (1092) ◽  
pp. 90-108 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Specific Heat ◽  
Temperature Variation ◽  
Temperature Region ◽  
Low Temperatures ◽  
Quartz Crystal ◽  
Corundum Crystal ◽  
Before And After ◽  
Dielectric Solids

An apparatus is described in which the thermal conductivity of solids can be determined at any temperature between 2 and 90°K. Several glasses and dielectric crystals have been measured. It had previously been found that at high temperatures the conductivity of glasses is proportional to the specific heat, but at low temperatures it falls off more slowly than the specific heat. The present experiments show that there is a temperature region in which the conductivity is nearly independent of temperature. A similar variation of conductivity is found for the thermo-plastic Perspex. The effect of lattice defects in crystals was studied by measuring the thermal conductivity of a quartz crystal before and after successive periods of neutron irradiation. After prolonged irradiation the conductivity approached, in both magnitude and temperature variation, that of quartz glass. Subsequent heating produced a substantial recovery in the conductivity. The results on both glasses and on crystals can be explained by the theory developed by Klemens (1951). Further measurements made on a corundum crystal confirm the importance of the ‘Umklapp’ processes, postulated by Peierls, in causing thermal resistance.

scholarly journals Coupling characteristics of meso-structure and thermophysical parameters of deep granite under high geo-temperature

2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4621-4629
Author(s):  
Huan Wang ◽  
Shuang You ◽  
Hong-Guang Ji ◽  
Hui-Ci Xu ◽  
Qi Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Constant ◽  
Structure Characteristics ◽  
Thermophysical Parameters ◽  
Before And After ◽  
Coupling Characteristics ◽  
Granite Samples

Polarizing microscope, nuclear magnetic resonance, and thermal constant analyzer were used to test the granite samples in the depth of 1500-2000 m in San?shandao before and after the heat treatment and be carried out to study the cor?responding relationship between rock meso-structure characteristics and different geothermal temperature circumstances, and the influence of thermal cycling on rock meso-structure. Tests results present that the porosity, pore size distribution, thermal conductivity and specific heat capacity are significantly affected by the environment where the rock occurs, mineral composition and particle size, and the increase in porosity and water content will cause the thermal conductivity and specific heat capacity to decrease.

scholarly journals Influence of Fabric Parameters on Thermal Comfort Performance of Double Layer Knitted Interlock Fabrics

2017 ◽  
Vol 17 (1) ◽  
pp. 20-26 ◽  
Author(s):  
Ali Afzal ◽  
Sheraz Ahmad ◽  
Abher Rasheed ◽  
Faheem Ahmad ◽  
Fatima Iftikhar ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Comfort ◽  
Specific Heat ◽  
Double Layer ◽  
Thermal Insulation ◽  
Loop Length ◽  
Knitted Fabrics ◽  
Thermal Transmittance ◽  
Thermal Absorptivity

Abstract The aim of this study was to analyse the effects of various fabric parameters on the thermal resistance, thermal conductivity, thermal transmittance, thermal absorptivity and thermal insulation of polyester/cotton double layer knitted interlock fabrics. It was found that by increasing fibre content with higher specific heat increases the thermal insulation while decreases the thermal transmittance and absorptivity of the fabric. It was concluded that double layer knitted fabrics developed with higher specific heat fibres, coarser yarn linear densities, higher knitting loop length and fabric thickness could be adequately used for winter clothing purposes.

Specific Heat and Thermal Conductivity of Superconducting UBe13and UPt3at Very Low Temperatures

1987 ◽  
Vol 26 (S3-2) ◽  
pp. 1217 ◽  
Author(s):  
H. R. Ott ◽  
E. Felder ◽  
A Bernasconi ◽  
Z. Fisk ◽  
J. L. Smith ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Low Temperatures

SPIN FLUCTUATIONS IN TCo2 STUDIED BY RESISTIVITY AND THERMOPOWER EXPERIMENTS (T = Y, Lu, Sc, Hf, Zr, Ce)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 370-373 ◽  
Author(s):  
N. BARANOV ◽  
E. BAUER ◽  
E. GRATZ ◽  
R. HAUSER ◽  
A. MARKOSYAN ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Low Temperatures ◽  
Spin Fluctuations ◽  
General Tendency ◽  
Electronic Specific Heat ◽  
Temperature Dependent

The temperature dependence of the resistivity and the thermopower in the region from 4.2K up to 1000K for the six isostructural paramagnetic compounds TCo 2 (T=Y, Lu, Sc, Hf, Zr, Ce) is studied. The resistivity ρ (T) follows a T 2 dependence at low temperatures in all these compounds. Plotting the A values into an A vs. γ2 diagram shows that YCo 2, LuCo 2, and ScCo 2 are spinfluctuation systems (A and γ denote the coefficients in ρ (T) = ρ0 + AT 2 and that of the electronic specific heat, respectively) HfCo 2 and ZrCo 2 do not fit into this general tendency in the ( A , γ2)-diagram. The temperature dependent thermopower S(T) in YCo 2, LuCo 2 and ScCo 2 exhibits a pronounced minimum in the low temperature region. These minima are obviously connected with the existence of spin fluctuations (paramagnon-drag). Spin fluctuations in HfCo 2 and ZrCo 2 are less important. This we conclude also from the ten times smaller A-values and the missing minimum in the thermopower at low temperatures.

Heat transfer in liquid helium below 1°K

1955 ◽  
Vol 231 (1187) ◽  
pp. 545-555 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Thermal Resistance ◽  
Specific Heat ◽  
Liquid Helium ◽  
Practical Importance ◽  
Heat Pulses

The thermal conductivity of liquid helium has been measured between 0.2 and 1.0° K. Below 0.6° K the heat flow is exactly proportional to the temperature gradient and the thermal conductivity is proportional to the specific heat and the diameter of the specimen. Thus the sole mechanism of heat transfer appears to be by phonons which are scattered only at the boundaries of the specimen. These results are in satisfactory accord with previous theoretical discussions and with measurements of the propagation of heat pulses in the liquid. The experiment also afforded the opportunity of making subsidiary measurements of the thermal resistance of the boundary between a metal and liquid helium. Besides being of practical importance, the results show that some modification is called for in the existing theoretical treatments.

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