Determination of the thermal conductivity of polypyrrole over the temperature range 280–335 K

1993 ◽  
Vol 28 (18) ◽  
pp. 5092-5098 ◽  
Author(s):  
B. A. Lunn ◽  
J. Unsworth ◽  
N. G. Booth ◽  
P. C. Innis
Keyword(s):  
Thermal Conductivity ◽  
Temperature Range

High Temperature Thermal Conductivity Measurements of Quasicrystalline Al70.8Pd20.9Mn8.3

2000 ◽  
Vol 626 ◽  
Author(s):  
Philip S. Davis ◽  
Peter A. Barnes ◽  
Cronin B. Vining ◽  
Amy L. Pope ◽  
Robert Schneidmiller ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Radiative Heat ◽  
Accurate Determination ◽  
Fourth Power ◽  
Radiative Effects ◽  
Radiative Heat Loss ◽  
3Ω Method ◽  
Temperature Range

ABSTRACTWe report measurements of the thermal conductivity on a potential high temperature thermoelectric material, the quasicrystal Al70.8Pd20.9Mn8.3. Thermal conductivity is determined over a temperature range from 30 K to 600 K, using both the steady state gradient method and the 3ω method. Measurements of high temperature thermal conductivity are extremely difficult using standard heat conduction techniques. These difficulties arise from the fact that heat is lost due to radiative effects. The radiative effects are proportional to the temperature of the sample to the fourth power and therefore can lead to large errors in the measured thermal conductivity of the sample, becoming more serious as the temperature increases. For thermoelectric applications in the high temperature regime, the thermal conductivity is an extremely important parameter to determine. The 3ω technique minimizes radiative heat loss terms, which will allow for more accurate determination of the thermal conductivity of Al70.8Pd20.9Mn8.3 at high temperatures. The results obtained using the 3ω method are compared to results from a standard bulk-thermal-conductivity-technique on the same samples over the temperature range, 30 K to 300 K.

scholarly journals Determination of the Radiation Exchange Factor in the Bundle of Steel Round Bars

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5263 ◽  
Author(s):  
Rafał Wyczółkowski ◽  
Marek Gała ◽  
Stanisław Szwaja ◽  
Andrzej Piotrowski
Keyword(s):  
Thermal Conductivity ◽  
Geometric Model ◽  
Initial Point ◽  
Temperature Range ◽  
Exchange Factor ◽  
Radiation Exchange ◽  
The Difference ◽  
Radiative Thermal Conductivity ◽  
Bar Diameter

A method to obtain a radiation exchange factor FR in the bundle of steel round bars is presented. This parameter is required for determination of the radiative thermal conductivity krd, which is one of the basic thermal properties of the bar bundles. In the presented approach, the analyzed parameter is calculated indirectly. The initial point for calculations is the geometric model of the medium defined as a unit cell. Then, for the elements present in this cell, the thermal resistance of both conduction and radiation is determined. The radiation resistance is calculated from the radiosity balance of the surfaces enclosing the analyzed system. On this basis, the radiation thermal conductivity krd is calculated. Next, taking into account the bar diameter, the value of parameter FR is also determined. The analysis is performed at the process temperature range of 200 to 800 °C for three bar diameters: 10, 20 and 30 mm, and for the three porosities of the bundle. Different emissivity of bars in the range of 0.5 to 0.9 was also taken into account. Finally, a relationship that allows calculating the FR factor correlated with the emissivity of the bars and the bundle porosity was established. The krd obtained from the methodology presented and compared with the values calculated directly do not exceed 9%; however, after averaging over the entire temperature range of the process, the difference does not exceed 0.2%.

Determination of Thermal Conductivity of Biomaterials in the Temperature Range 233–313K Using a Tiny Detector Made of a Self-Heated Thermistor

2002 ◽  
Vol 1 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Haifeng Zhang ◽  
Shuxia Cheng ◽  
Liqun He ◽  
Aili Zhang ◽  
Ying Zheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Range

Optical Determination of Thermal Conductivity with a Plane Source Technique

1968 ◽  
Vol 23 (5) ◽  
pp. 682-686 ◽  
Author(s):  
Silas E. Gustafsson ◽  
Nils-Olov Halling ◽  
Rolf A. E. Kjellander
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Temperature Dependence ◽  
Theoretical Approach ◽  
Experimental Results ◽  
Plane Source ◽  
Melting Points ◽  
Temperature Range ◽  
Optical Determination

The thermal conductivity and the thermal diffusivity of the three alkali nitrates LiNO3 , RbNO3 and CsNO3 have been measured over a temperature range between 50° and 100 °C above their melting points. Any temperature dependence of the thermal conductivity cannot be established for any of the investigated liquids but the results indicate that it must be less than 10-3 °C-1. The experimental results are compared with the conductivities which can be calculated with already excisting theories. A somewhat modified theoretical approach is suggested for estimating the thermal conductivity, where no adjustable parameters are being used. The experimental and theoretical values at the melting points agree within about 10 percent.

scholarly journals The thermal conductivity of vitreous silica, with a note on crystalline quartz

1926 ◽  
Vol 113 (764) ◽  
pp. 335-351 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Scientific Work ◽  
Vitreous Silica ◽  
Crystalline Quartz ◽  
Temperature Range ◽  
Physical Constants ◽  
Extended Application ◽  
The Mean

Vitreous silica is a material which finds extended application in many branches of scientific work, and considerable attention has been given to some of its physical constants. Little work has, however, been done on the thermal conductivity. Eucken and Barratt appear to be the only workers who have attacked the problem, their results being by no means in agreement, as is shown in Table I. This paper gives an account of a determination of the thermal conductivity of clear transparent vitreous silica over a temperature range of approximately 60° to 240°C. The value obtained for the conductivity at 100°C. is 0.00338, and for the mean change of conductivity per °C. 0.0000018 5 . Thus the figures do not agree with the results of either Eucken or Barratt, except that the latter’s value for the conductivity increment per °C. is of the same order as that found in the present work.

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