scholarly journals Thermal properties of wood measured by the hot-disk method: comparison with thermal properties measured by the steady-state method

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Kei Maeda ◽  
Yuko Tsunetsugu ◽  
Kohta Miyamoto ◽  
Tatsuya Shibusawa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Steady State ◽  
Thermal Diffusivity ◽  
Geometric Mean ◽  
Tangential Section ◽  
Steady State Method ◽  
Hot Disk ◽  
State Method ◽  
Disk Method

AbstractThe hot-disk method is a transient method for the measurement of thermal properties. This method can measure both the thermal conductivity and thermal diffusivity in a short time for isotropic materials. To establish a method for measuring the thermal properties of wood by the hot-disk method, the relationship between the thermal properties of wood obtained by the hot-disk method and those obtained by the steady-state method was investigated. The thermal properties were measured by the hot-disk method using small pieces of kiri (Paulownia tomentosa), sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), yachidamo (Fraxinus mandshurica), and buna (Fagus crenata) when the hot-disk sensor was in contact with the cross section, radial section, and tangential section. The thermal conductivities in the longitudinal, radial, and tangential directions were also measured by the comparison method using the same specimen. The thermal properties obtained by the hot-disk method and the steady-state method were compared, based on the assumption that the thermal diffusivity measured by the hot-disk method was the geometric mean of that in the two main directions in the plane of the sensor, and the thermal conductivity measured by the hot-disk method was a power of that in three main directions. As a result, the thermal conductivity obtained by the hot-disk method was 10–20% higher than that obtained by the steady-state method; the thermal diffusivity measured by the hot-disk method was equal to that obtained by the steady-state method on average, while in the former thermal diffusivity varied widely. These results were found to be explainable in terms of the Dufour effect, which is the heat flow induced by the mass flow caused by the heating of the sensor, and the existing findings on the time dependence of the sensitivity coefficient in the hot-disk method. The present study proposed two methods for calculating the thermal properties of wood from the hot-disk method were proposed, and it was found that the errors between the obtained thermal properties and those obtained by the steady-state method differed depending on the calculation method.

scholarly journals Numerical Simulation of Thermal Conductivity of Foam Glass Based on the Steady-State Method

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 54 ◽  
Author(s):  
Zipeng Qin ◽  
Gang Li ◽  
Yan Tian ◽  
Yuwei Ma ◽  
Pengfei Shen
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Heat Flow ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Foam Glass ◽  
Orthogonal Experimental Design ◽  
Carbonate Content ◽  
Steady State Method ◽  
State Method

The effects of fly ash, sodium carbonate content, foaming temperature and foaming time on foam glass aperture sizes and their distribution were analyzed by the orthogonal experimental design. Results from the steady-state method showed a normal distribution of the number of apertures with change in average aperture, which ranges from 0.1 to 2.0 mm for more than 93% of apertures. For a given porosity, the thermal conductivity decreases with the increase of the aperture size. The apertures in the sample have obvious effects in blocking the heat flow transmission: heat flow is quickly diverted to both sides when encountered with the aperture. When the thickness of the sample is constant, the thermal resistance of the foam glass sample increases with increasing porosity, leading to better thermal insulation. Furthermore, our results suggest that the more evenly distributed and orderly arranged the apertures are in the foam glass material, the larger the thermal resistance of the material and hence, the better the thermal insulation.

A Spherical Steady-State Method to Measure Soil Thermal Conductivity

2019 ◽  
Vol 52 (12) ◽  
pp. 1572-1576
Author(s):  
S. M. Mahdavi ◽  
M. R. Neyshabouri ◽  
H. Fujimaki
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Soil Thermal Conductivity ◽  
Steady State Method ◽  
State Method

Film Cooling Performance for Combustor Wavy Liner-wall Evaluated by Steady-state Method Using Two Different Thermal-conductivity Materials

2017 ◽  
Vol 2017.23 (0) ◽  
pp. 517
Author(s):  
Hitoshi Taniguchi ◽  
Ryosuke Kondo ◽  
Akira Murata ◽  
Hiroshi Saito ◽  
Kaoru Iwamoto ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Film Cooling ◽  
Cooling Performance ◽  
Steady State Method ◽  
State Method

scholarly journals Thermal Conductivity of Steam at Atmospheric Pressure

1969 ◽  
Vol 11 (4) ◽  
pp. 392-401 ◽  
Author(s):  
T. J. S. Brain
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Steady State ◽  
Atmospheric Pressure ◽  
Concentric Cylinder ◽  
Temperature Range ◽  
Steady State Method ◽  
New Correlation ◽  
Paper Work ◽  
State Method

In this paper work carried out by the author to measure the thermal conductivity of steam at atmospheric pressure in the temperature range 100-700°C is reported. This work was undertaken in view of the discrepancies which exist in the experimental data at atmospheric pressure. In particular, the serious differences which exist at the high temperatures between the results of Russian experimenters, who give higher values than those given by American and German workers, needed investigation. Utilizing two concentric cylinder cells an absolute steady state method has been used to measure the thermal conductivity of steam in the temperature range 100-700°C, at atmospheric pressure, with a probable accuracy estimated to be within ± l·5-±2 per cent. The results obtained confirm Russian observations at the higher temperatures and it is hoped that these results will help finally to resolve the inconsistencies in the experimental data. A fresh assessment of all the experimental data is given by the author where arguments in favour of both the lower and higher atmospheric lines are discussed. A new correlation of experimental data has been undertaken and a reduction in the tolerances put on the equation defining the atmospheric line from ±3 per cent in the range 100-400°C and ±4 per cent in the range 400-700°C to ±2 per cent over the complete range 100-700°C is now recommended.

Thermal Conductivity of Molybdenum; Test of Steady-state Method from 1.5 K to 40 K

2004 ◽  
Vol 54 (S4) ◽  
pp. 567-570 ◽  
Author(s):  
K. Tibenská ◽  
A. Orendáčová ◽  
M. Orendáč ◽  
A. Vlček ◽  
A. Feher
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Steady State Method ◽  
State Method
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