scholarly journals Investigation of the dependence of the thermophysical properties of seasonally freezing soil under the foundations of foundations on their humidity, density and depth of the pit

2020 ◽  
Vol 78 (4) ◽  
pp. 184-192
Keyword(s):  
Thermal Conductivity ◽  
Soil Moisture ◽  
Thermophysical Properties ◽  
Practical Importance ◽  
Underground Structures ◽  
Thermal Methods ◽  
Freezing Soil ◽  
Chemical Reagents ◽  
Current State ◽  
Coefficient Of Thermal Conductivity

As a result of the analysis of the current state of the foundation and foundations in the conditions of seasonally freezing soils, the study of thermophysical properties is of great practical importance for the construction of many underground structures. Research in this direction is especially important for local thawing of soil using thermal methods and various chemical reagents. The article presents the results of a scientific - experimental study to establish patterns of change in the physical characteristics of the soil and the coefficient of thermal conductivity of the soil from the dominant factors in the following systems: depth of soil sampling – soil moisture; sampling depth – soil density; soil moisture – coefficient of soil thermal conductivity.

scholarly journals Thermophysical Properties of Cement Mortar Containing Waste Glass Powder

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 488
Author(s):  
Oumaima Nasry ◽  
Abderrahim Samaouali ◽  
Sara Belarouf ◽  
Abdelkrim Moufakkir ◽  
Hanane Sghiouri El Idrissi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Glass Powder ◽  
Cement Mortar ◽  
Soda Lime ◽  
Waste Glass ◽  
Soda Lime Glass ◽  
Volumetric Specific Heat ◽  
Waste Glass Powder

This study aims to provide a thermophysical characterization of a new economical and green mortar. This material is characterized by partially replacing the cement with recycled soda lime glass. The cement was partially substituted (10, 20, 30, 40, 50 and 60% in weight) by glass powder with a water/cement ratio of 0.4. The glass powder and four of the seven samples were analyzed using a scanning electron microscope (SEM). The thermophysical properties, such as thermal conductivity and volumetric specific heat, were experimentally measured in both dry and wet (water saturated) states. These properties were determined as a function of the glass powder percentage by using a CT-Meter at different temperatures (20 °C, 30 °C, 40 °C and 50 °C) in a temperature-controlled box. The results show that the thermophysical parameters decreased linearly when 60% glass powder was added to cement mortar: 37% for thermal conductivity, 18% for volumetric specific heat and 22% for thermal diffusivity. The density of the mortar also decreased by about 11% in dry state and 5% in wet state. The use of waste glass powder as a cement replacement affects the thermophysical properties of cement mortar due to its porosity as compared with the control mortar. The results indicate that thermal conductivity and volumetric specific heat increases with temperature increase and/or the substitution rate decrease. Therefore, the addition of waste glass powder can significantly affect the thermophysical properties of ordinary cement mortar.

EXAMINATION OF THERMOPHYSICAL CHARACTERISTICS OF A HEAT-PROTECTIVE MATERIAL BASED ON FIBERGLASS DURING DESTRUCTION

2021 ◽  
pp. 91-97
Author(s):  
D.Ya. Barinov ◽  
◽  
S.Yu. Shorstov ◽  
M.G. Razmahov ◽  
A.I. Gulyaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermophysical Properties ◽  
Thermal Effects ◽  
Space Technology ◽  
Muffle Furnace ◽  
Thermophysical Characteristics ◽  
Initial State ◽  
Protective Material ◽  
Temperature Dependences

When designing advanced samples of aviation and rocket and space technology, during the operation of which the temperature on the surface of the material can exceed the temperature of destruction, it is important to have an understanding of the values of thermophysical properties. The work investigates the thermophysical properties of fiberglass in the initial state and after the binder is burned out in a muffle furnace. The temperature dependences of thermal effects, heat capacity, thermal diffusivity and thermal conductivity were determined, density was measured, and thermogravimetric analysis was carried out. Using a stereomicroscope, the microstructure of the lateral cut of the samples was examined and its evolution was determined during the burning of the binder.

Assessment of the technical condition of underground structures of the largest hydroelectric power station in the North Caucasus, the Chirkeyskaya HPP

2021 ◽  
Vol 18 (3) ◽  
pp. 410-420
Author(s):  
Vladimir N. KAVKAZKY ◽  
◽  
Yana V. MEL’NIK ◽  
Alexey P. LEIKIN ◽  
Andrey V. BENIN ◽  
...  
Keyword(s):  
Large Scale ◽  
Practical Importance ◽  
Hydroelectric Power Plant ◽  
Technical Condition ◽  
Hydroelectric Power Station ◽  
Hydroelectric Power ◽  
Underground Structures ◽  
North Caucasus ◽  
The Caucasus ◽  
The North

Objective: Chirkeyskaya HPP is by far the most powerful hydroelectric power plant in the North Caucasus with the highest arched dam in Russia and the second highest dam in the country after the Sayano-Shushenskaya HPP. This explains why it is called the pearl of the Caucasus. Methods: For the operation and maintenance of this unique structure, a large-scale complex of underground structures for various purposes was built, the technical condition of which must be constantly monitored. To carry out work on the survey of underground structures, the management of the design and survey institute of JSC “Lengidroproekt” decided to attract specialists from the Department of Tunnels and Subways and the Test Center “Strength” of Emperor Alexander I Petersburg State Transport University. The work was successfully carried out at the end of 2015. Results: The safety of underground structures was objectively assessed. Recommendations for the repair and further comprehensive reconstruction of the Chirkeyskaya HPP have been developed. Practical importance: Carry out work on the survey of underground structures of Chirkeyskaya HPP is allowes elaborate of complex measures on safety from Chirkeyskaya HPP.

Determination of the Thermal Properties of a PCB by Coupled Numerical and Experimental Approach

2020 ◽  
Author(s):  
Yener Usul ◽  
Mustafa Özçatalbaş
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Numerical Analysis ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Analyses ◽  
Analysis Model ◽  
Linear Temperature ◽  
Coefficient Of Thermal Conductivity

Abstract Increasing demand for usage of electronics intensely in narrow enclosures necessitates accurate thermal analyses to be performed. Conduction based FEM (Finite Element Method) is a common and practical way to examine the thermal behavior of an electronic system. First step to perform a numerical analysis for any system is to set up the correct analysis model. In this paper, a method for obtaining the coefficient of thermal conductivity and specific heat capacity of a PCB which has generally a complex composite layup structure composed of conductive layers, and dielectric layers. In the study, above mentioned properties are obtained performing a simple nondestructive experiment and a numerical analysis. In the method, a small portion of PCB is sandwiched from one side at certain pressure by jaws. A couple of linear temperature profiles are applied to the jaws successively. Unknown values are tuned in the analysis model until the results of FEM analysis and experiment match. The values for the coefficient of thermal conductivity and specific heat capacity which the experiment and numerical analysis results match can be said to be the actual values. From this point on, the PCB whose thermal properties are determined can be analyzed numerically for any desired geometry and boundary condition.

scholarly journals PECULIARITIES OF KINETICS OF THE COEFFICIENT OF THERMAL CONDUCTIVITY DEPENDING ON THE HUMIDITY RATE OF WALL BLOCKS MADE OF AGRICULTURAL WASTES

2019 ◽  
Vol 4 (10) ◽  
pp. 19-28 ◽  
Author(s):  
А. Должонок ◽  
A. Dolzhonok ◽  
А. Бакатович ◽  
A. Bakatovich
Keyword(s):  
Thermal Conductivity ◽  
Building Materials ◽  
Moisture Absorption ◽  
Coarse Aggregate ◽  
Sustainable Use ◽  
Agricultural Wastes ◽  
Hygroscopic Moisture ◽  
Relative Air Humidity ◽  
Coefficient Of Thermal Conductivity ◽  
Kinetics Of

The article considers the prospect of plant wastes usage as aggregates while constructing new building materials in the form of wall blocks. The results of the research on water absorption of the wall blocks at the relative air humidity of 97 % are presented. The kinetics of change in humidity and the coefficient of thermal conductivity of the blocks with the rye and buckwheat straw coarse aggregate, and also the blocks with fine coarse aggregate of flax boon and atomized buckwheat are analyzed. Empirical dependences of the coefficient of thermal conductivity on the rate of humidity of wall blocks are obtained from experimental observations. After the maximum rate of hygroscopic moisture absorption, the best indexes are recorded on the blocks made of flax and straw. The humidity rate of the composite does not exceed 10,9 % with the increase of thermal conductivity up to 0.104 W/(m•°С). In the result of the research, the solution to the sustainable use of agricultural wastes to get environmental responsible building materials is proposed. Blocks can be are used in the erection of supporting and filler walls in one-story buildings and multistoried frame housing construction when filling exterior wall openings.

scholarly journals Application and testing of a new simple experimental set-up for thermal conductivity measurements of liquids

2017 ◽  
Vol 21 (3) ◽  
pp. 1195-1202 ◽  
Author(s):  
Andrej Stanimirovic ◽  
Emila Zivkovic ◽  
Nenad Milosevic ◽  
Mirjana Kijevcanin
Keyword(s):  
Thermal Conductivity ◽  
Measurement Uncertainty ◽  
Thermophysical Properties ◽  
Deionized Water ◽  
Conductivity Measurements ◽  
Transient Hot Wire ◽  
Hot Wire ◽  
New Apparatus ◽  
Wire Method ◽  
Set Up

Transient hot wire method is considered a reliable and precise technique for measuring the thermal conductivity of liquids. The present paper describes a new transient hot wire experimental set-up and its initial testing. The new apparatus was tested by performing thermal conductivity measurements on substances whose reference thermophysical properties data existed in literature, namely on pure toluene and double distilled deionized water. The values of thermal conductivity measured in the temperature range 25 to 45 ?C deviated +2.2% to +3% from the literature data, while the expanded measurement uncertainty was estimated to be ?4%.

scholarly journals Thermal conductivity of silicon doped by phosphorus: ab initio study

2018 ◽  
Vol 35 (4) ◽  
pp. 717-724
Author(s):  
B. Andriyevsky ◽  
W. Janke ◽  
V.Yo. Stadnyk ◽  
M.O. Romanyuk
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Phonon Scattering ◽  
Theoretical Calculations ◽  
Doped Semiconductors ◽  
Silicon Crystals ◽  
Coefficient Of Thermal Conductivity ◽  
Silicon Doped ◽  
Scattering Time ◽  
Phosphorus Doped

Abstract An original approach to the theoretical calculations of the heat conductivity of crystals based on the first principles molecular dynamics has been proposed. The proposed approach exploits the kinetic theory of phonon heat conductivity and permits calculating several material properties at certain temperature: specific heat, elastic constant, acoustic velocity, mean phonon scattering time and coefficient of thermal conductivity. The method has been applied to silicon and phosphorus doped silicon crystals and the obtained results have been found to be in satisfactory agreement with corresponding experimental data. The proposed computation technique may be applied to the calculations of heat conductivity of pure and doped semiconductors and isolators.

scholarly journals XVI Международная конференция "Термоэлектрики и их применения --- 2018" (ISCTA 2018), Санкт-Петербург, 8-12 октября 2018 г. Влияние неидеальности геометрической формы образца на неопределенность измерений теплопроводности методом лазерной вспышки

2019 ◽  
Vol 53 (6) ◽  
pp. 731
Author(s):  
А.В. Асач ◽  
Г.Н. Исаченко ◽  
А.В. Новотельнова ◽  
В.Е. Фомин ◽  
К.Л. Самусевич ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Measurement Uncertainty ◽  
Conductivity Measurement ◽  
Laser Flash ◽  
Comsol Multiphysics ◽  
Flash Method ◽  
Cylindrical Shape ◽  
Plane Parallel ◽  
Coefficient Of Thermal Conductivity ◽  
Truncated Cylinder

The influence of the geometric shape of the samples on the uncertainty of the coefficient of thermal conductivity measurement of materials by the method of a laser flash has been studied. Using a method of mathematical modeling in the Comsol Multiphysics software, a model that simulates the process of measuring the coefficient of thermal conductivity of samples made of graphite, Mg2Si0.4Sn0.6 and bismuth telluride using a laser flash method has been created. Samples of cylindrical shape with plane-parallel sides and samples in the form of a truncated cylinder, as well as samples in the form of a parallelepiped with a square base, were investigated. It is shown that the measurement uncertainty of samples with plane-parallel sides and sizes up to 12.7 mm, does not exceed 2%. For samples in the form of a truncated cylinder with a diameter of 3 mm and at an angle of ϕ= 1.5°, the measurement uncertainty does not exceed 3%. With an increase in the sample diameter and the ϕ angle, the measurement uncertainty increases significantly.

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