Determination of the coefficient of thermal conductivity of glass and polymer fibers

1969 ◽  
Vol 26 (9) ◽  
pp. 523-526 ◽  
Author(s):  
O. F. Shlenskii ◽  
N. I. Goncharuk ◽  
V. Ya. Gal'tsov
Keyword(s):  
Thermal Conductivity ◽  
Polymer Fibers ◽  
Coefficient Of Thermal Conductivity

scholarly journals Characteristics and properties of Bitlis ignimbrites and their environmental implications

2020 ◽  
Vol 70 (338) ◽  
pp. 214
Author(s):  
E. Işık ◽  
A. Büyüksaraç ◽  
E. Avşar ◽  
M. F. Kuluöztürk ◽  
M. Günay
Keyword(s):  
Thermal Conductivity ◽  
Construction Material ◽  
Metal Extraction ◽  
Ultrasonic Speed ◽  
Environmental Implications ◽  
Volcanic Origin ◽  
Speed Test ◽  
Subsequent Transformation ◽  
Coefficient Of Thermal Conductivity

Bitlis rock is used as a construction material and comes from the lava emitted by volcanoes and their subsequent transformation into ignimbrites. This type of rocks has been characterized physically, chemi­cally, toxicologically and radioactively using different procedures including determination of the coefficient of thermal conductivity, gamma spectrometry, ultrasonic speed test, ICP masses and metal extraction. The results indicate that Bitlis rocks have an ACI greater than 1, although their content of radon is lower than other rocks of volcanic origin. Leaching of metals from these rocks indicates that Pb and Cd can provide an infiltration level in the field higher than the level permitted by TCLP and they have undesired toxicological risks. The percent­ages of extraction of other metals also point to this infiltration problem. Despite this, the material offers good qualities for usage as a building material such as its thermal coefficients.

Investigation of the Thermal Conductivity of Rubber

1938 ◽  
Vol 11 (2) ◽  
pp. 359-371 ◽  
Author(s):  
L. Frumkin ◽  
Yu Dubinker
Keyword(s):  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Carbon Black ◽  
Natural Rubber ◽  
Considerable Increase ◽  
Large Percentage ◽  
K Value ◽  
Synthetic Rubber ◽  
Coefficient Of Thermal Conductivity

Abstract 1. The apparatus for the determination of the coefficients of thermal conductivity which is described is satisfactory for the investigation of rubber mixtures. 2. A review of the results of the determinations of K values of various mixtures leads to the following conclusions: (a) The thermal conductivity of rubber mixtures containing synthetic rubber is greater than that of mixtures containing natural rubber. (b) The addition of zinc oxide even in considerable quantities to rubber mixtures containing a large percentage (55 per cent) of carbon black does not substantially increase thermal conductivity. (c) In the case of carcass mixtures a considerable increase in the coefficient of thermal conductivity is observed when the content of zinc oxide is increased from 7.5 to 15 per cent by weight; on further increase in the zinc oxide K increases but little. (d) The K value of carcass mixtures before vulcanization is smaller than that of the same mixtures after vulcanization by an average of 23 per cent. (e) The thermal conductivity of uncured tread mixtures is the same as that of vulcanized mixtures. (f) The coefficient of vulcanization has no effect on the K value of unloaded mixtures and mixtures containing fillers. (g) The K value of rubber mixtures increases sharply with addition up to 60 per cent by volume of fillers with good thermal conductivity (zinc oxide and graphite), but only slowly with the addition of fillers of medium thermal conductivity (carbon black). In other words, the curve of the relation between the coefficient of thermal conductivity and the percentage by volume of graphite and of zinc oxide is convex to the filler axis and is concave in the case of carbon black.

Determination of Thermal Conductivity on Lightweight Concretes

2016 ◽  
Vol 677 ◽  
pp. 163-168
Author(s):  
Lenka Bodnárová ◽  
Jitka Peterková ◽  
Jiri Zach ◽  
Kateřina Sovová
Keyword(s):  
Thermal Conductivity ◽  
High Temperatures ◽  
Structural Changes ◽  
Lightweight Concrete ◽  
Thermal Insulating ◽  
Coefficient Of Thermal Conductivity ◽  
The Matrix ◽  
Wire Method ◽  
Insulating Properties

A range of testing methods were used to study the potential structural changes as a result of the effects of high temperatures on lightweight types of concrete developed above all for fire resistant structures. One such test for monitoring changes in concrete structures is the non-stationary determination of the coefficient of thermal conductivity using the hot wire method. The matrix structure progressively collapses as a result of the effects of high temperatures on the concrete structure ́s surface because erosion takes place of the matrix and aggregate porous structures. The degradation of the porosity of the concrete results in the deterioration of its thermal insulating properties. This paper assesses the dependence of the thermal conductivity coefficient of lightweight concretes on temperature and determines the potential occurrence of structural changes in the lightweight concrete matrix. The results were verified using other methods to determine the concrete ́s resistance to thermal load.

Structure and Thermophysical Properties of Coatings Formed by the Method of Microarc Oxidation on an Aluminum Alloy AK4-1

2018 ◽  
Vol 284 ◽  
pp. 1235-1241 ◽  
Author(s):  
N.Yu. Dudareva ◽  
A.B. Kruglov ◽  
R.F. Gallyamova
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Alloy ◽  
Methodological Approach ◽  
Microarc Oxidation ◽  
Layer By Layer ◽  
Properties Of Coatings ◽  
X Ray ◽  
Coefficient Of Thermal Conductivity ◽  
Pulsed Laser Heating

The work presents the results of investigation of the thermal conductivity of the coating formed by the method of microarc oxidation (MAO) on a deformable aluminum alloy AK4-1. The article describes the methodology of the research including the formation of the MAO layer, the study of the structure and composition of the coating and the determination of its coefficient of thermal conductivity. The methodological approach to determining the thermal conductivity is based on measuring the thermal diffusivity of the oxide layer by pulsed laser heating, as well as calculating the heat capacity and density of the coating based on the data of layer-by-layer X-ray phase analysis is proposed. During the calculations, the porosity of the coating was taken into account. In accordance with the proposed procedure, it is established that the MAO layer has a thermal conductivity coefficient of ~ 5 W/(mK). The value obtained is comparable with the known results, but is significantly lower than the values of the thermal conductivity of the single phases constituting the coating. It is assumed that this effect is related to the feature of the structure of the MAO layer.

scholarly journals Estimation of thermal conductivity of snow by its density and hardness in Svalbard

2018 ◽  
Vol 58 (3) ◽  
pp. 343-352 ◽  
Author(s):  
V. M. Kotlyakov ◽  
A. V. Sosnovsky ◽  
N. I. Osokin
Keyword(s):  
Thermal Conductivity ◽  
Snow Cover ◽  
Ice Crystals ◽  
Natural Occurrence ◽  
Svalbard Archipelago ◽  
Good Convergence ◽  
Coefficient Of Thermal Conductivity ◽  
The Relationship

The results of experimental investigation of thermal conductivity of snow on the Svalbard archipelago in the conditions of natural occurrence are considered. The observations were carried out in the spring of 2013–2015 in the vicinity of the meteorological station «Barentsburg». The obtained data were processed using the Fourier equation of thermal conductivity that allowed determination of the coefficient t of thermal conductivity of the snow with different structure and density. The thermal conductivity of snow depends on the contacts between ice crystals. The larger the contact area, the better the heat transfer from one layer to another. But the strength characteristics of snow, and especially its hardness, depend on the bonds between ice crystals, so the thermal conductivity and hardness of snow depend on the structure of snow. Note, that measurements of snow hardness are less laborious than measurements of its thermal conductivity. For layers of snow cover of different hardness the relationship between snow thermal conductivity and its density has been established. To verify the reliability of the approach to the determination of snow thermal conductivity, numerical experiments were performed on a mathematical model, which did show good convergence of the results. The obtained formulas for the coefficient of thermal conductivity of very loose, loose, medium and hard snow (according to the international classification of seasonal snow falls) are compared with the data of other studies. It was found that when the snow density is within the range 0.15–0.40 g/cm3 these formulas cover the main variety of thermal conductivity of snow. This allows estimating the coefficient of thermal conductivity and to determine the thermal resistance of snow cover in the field by measuring the density and hardness of different layers of snow.

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