scholarly journals Physicochemical mechanisms of the growth of oxide crystals on the surface of tungsten conductors heated by electric current

2021 ◽  
pp. 117-126
Author(s):  
S.G. Orlovskaya
Keyword(s):  
Electric Current ◽  
Crystal Structures ◽  
Experimental Studies ◽  
Longitudinal Direction ◽  
Current Strength ◽  
Large Temperature ◽  
Basic Oxide ◽  
Carbon Particles ◽  
Crystalline Oxide ◽  
Initial Stage

Physical and mathematical modeling of stationary thermal modes of heating and oxidation of tungsten conductors heated by electric current in air has been carried out. The dependences of the stationary temperature of the conductor on the strength of the heating current are obtained. The critical values of the current strength are found, which determine the transitions to the unsteady oxidation regime. The results of calculating the temperature regimes describe well the experimental data obtained by us using the electrothermographic method. As a result of experimental studies, the features of the appearance and growth of crystalline oxide structures on the surface of an oxidizing tungsten conductor have been studied. The temperatures at which filamentous crystals appear on the tungsten surface are determined, and the regularities of their growth are investigated. A physicochemical mechanism of the formation and growth of crystalline oxide structures on the surface of a tungsten conductor is proposed. It was found that carbon particles, which are part of the impurity, are the reason for the formation of nitrate crystals of tungsten trioxide on the basic oxide. With an increase in the temperature of the sample, the filaments grow, branch out and transform into dendritic structures of a complex bush-like shape. It has been proven that the rapid growth of crystal structures occurs due to the deposition of clusters and microgranules of  WO3 oxide from the gas phase on the crystallization centers on the surface of the conductor. At the initial stage, these are impurity particles or mechanical inhomogeneities of the basic oxide, then a growing crystal. Clusters arise due to large temperature gradients at the surface of the conductor. It has been established that carbon atoms can migrate along the branches of oxide crystal structures. It was found that at the initial stage the crystals grow more intensively in the longitudinal direction. However, upon reaching a certain height, they begin to expand intensively in the transverse direction. The growth rates of crystal structures in the longitudinal and transverse directions are found.

scholarly journals Melting Point of Carbon Particles behind the Gas Detonation Front

2022 ◽  
Vol 16 (2) ◽  
pp. 59-70
Author(s):  
E. S. Prokhorov
Keyword(s):  
Melting Point ◽  
Detonation Front ◽  
Molar Fraction ◽  
Experimental Studies ◽  
Oxygen Mixture ◽  
Detonation Products ◽  
Gas Detonation ◽  
Nanoscale Particles ◽  
Carbon Particles ◽  
Carbon Condensate

A mathematical model of gas detonation of fuel-enriched mixtures of hydrocarbons with oxygen has been formulated, which makes it possible to numerically study the equilibrium flows of detonation products in the presence of free carbon condensation. Reference data for graphite were used to describe the thermodynamic properties of carbon condensate. The calculations are compared with the known results of experimental studies in which, when detonating an acetylene-oxygen mixture in a pipe closed at one end, it is possible to obtain nanoscale particles from a carbon material with special properties. It is assumed that the melting point of such a material is lower than that of graphite and is about 3100 K. Only with such an adjustment of the melting temperature, the best agreement (with an accuracy of about 3 %) was obtained between the calculated and experimental dependence of the detonation front velocity on the molar fraction of acetylene in the mixture.

scholarly journals Development of unsteady boundary layers on the generatrices of a vertical silicon rod heated by electric current in the mode of conjugate radiation-convective heat transfer

2021 ◽  
Vol 2119 (1) ◽  
pp. 012163
Author(s):  
A. V. Mitina ◽  
V. S. Berdnikov ◽  
K. A. Mitin
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Convective Heat Transfer ◽  
Electric Current ◽  
Convective Heat ◽  
Longitudinal Direction ◽  
Longitudinal Distribution ◽  
Grashof Number ◽  
Inhomogeneous Temperature ◽  
Inhomogeneous Temperature Field

Abstract The nonstationary conjugate radiation-convective heat transfer of a single silicon rod heated by an electric current with the surrounding gas medium is studied numerically in the axisymmetric formulation by the finite element method. The calculations were carried out at the Prandtl number Pr = 0.68, and the range of the Grashof number, determined by the temperature difference and the radius of the rod 9 703 ≤ Gr ≤ 261 977. It is shown that after a short incubation period, a circulation flow is formed. As a result, a significantly inhomogeneous temperature field in the longitudinal direction is formed in a silicon rod heated by an electric current. As the Grashof number increases, the inhomogeneity of the longitudinal distribution of the temperature field increases.

scholarly journals Validation of experimental molecular crystal structures with dispersion-corrected density functional theory calculations

2010 ◽  
Vol 66 (5) ◽  
pp. 544-558 ◽  
Author(s):  
Jacco van de Streek ◽  
Marcus A. Neumann
Keyword(s):  
Density Functional Theory ◽  
Crystal Structures ◽  
Density Functional ◽  
Unit Cell ◽  
Organic Crystal ◽  
Large Temperature ◽  
Unit Cell Parameters ◽  
Functional Theory ◽  
Cell Parameters ◽  
Experimental Crystal

This paper describes the validation of a dispersion-corrected density functional theory (d-DFT) method for the purpose of assessing the correctness of experimental organic crystal structures and enhancing the information content of purely experimental data. 241 experimental organic crystal structures from the August 2008 issue of Acta Cryst. Section E were energy-minimized in full, including unit-cell parameters. The differences between the experimental and the minimized crystal structures were subjected to statistical analysis. The r.m.s. Cartesian displacement excluding H atoms upon energy minimization with flexible unit-cell parameters is selected as a pertinent indicator of the correctness of a crystal structure. All 241 experimental crystal structures are reproduced very well: the average r.m.s. Cartesian displacement for the 241 crystal structures, including 16 disordered structures, is only 0.095 Å (0.084 Å for the 225 ordered structures). R.m.s. Cartesian displacements above 0.25 Å either indicate incorrect experimental crystal structures or reveal interesting structural features such as exceptionally large temperature effects, incorrectly modelled disorder or symmetry breaking H atoms. After validation, the method is applied to nine examples that are known to be ambiguous or subtly incorrect.

PENGARUH BAYANGAN TERHADAP OUTPUT TEGANGAN DAN KUAT ARUS PADA PEMBANGKIT LISTRIK TENAGA SURYA (PLTS)

ROTOR ◽  
2018 ◽  
Vol 11 (2) ◽  
pp. 47
Author(s):  
Hattu P D Edwin ◽  
Wabang A Jhon ◽  
Tuati Ambros ◽  
Palinggi Aris
Keyword(s):  
Solar Cell ◽  
Electric Current ◽  
Output Voltage ◽  
Electrical Energy ◽  
Current Strength ◽  
The Sun ◽  
Solar Panels ◽  
Shadow Area ◽  
Strong Current ◽  
Cloud Condition

Electrical energy is a very important requirement for the community, along with the development of the era and technological advances that are urgently needed, the need for electrical energy is very large, while the source of electricity that is currently being used still uses energy derived from fossil fuels. As we know that the source of energy derived from fossils is very limited, therefore other energy sources are sought or we are more familiar with renewable energy, one of which is the energy source that comes from the sun, which is better known as solar cell. The electricity from this solar cell is very dependent on sunlight which must illuminate the solar panels so that solar energy can be converted into electrical energy. The output from these solar panels is in the form of voltage and electric current. Some factors that can affect the amount of output or output voltage of electric current in PLTS is, temperature, shadow, (cloud condition, and surrounding environment), and wind speed. Therefore, the purpose of this research is to find out how much the shadow effect on the output voltage and electric current produced by PLTS. It is expected that this research can increase the knowledge of energy derived from the sun in this case the solar cell and know the effect of the shadow on the output voltage and electric current from solar panels.The results showed that there was a shadow effect on voltage reduction and current strength in the PLTS system, namely the 10% shadow area and 12.44 volt DC solar panel current and 2.54 amperage, 100% area covering the voltage output panel and the current of solar panels 12.10 volt DC and 0.22 amperage. The area of the shadow that covers the solar panel affects the output voltage and the strong current of the battery that is the area of the shadow 10% voltage and strong current battery 12.35 volt DC and 18.54 amper, 100% area cover the output panel voltage and strong current battery 11.90 volt DC and 13.85 amperes The shadow area covering the solar panels influences the output voltage and current strength of the inverter, namely the area of the shadow 10% voltage and 226.4 volt AC inverter current and 0.97 amperage, 100% covering the output voltage panel and 220.2 volt AC and 0.66 amperage current. Keywords: Electrical energy, Solar cell, Shadow (cloud condition)

scholarly journals Numerical and Experimental Study of Phase Transformations in Welding Processes / Badania Numeryczne I Doświadczalne Przemian Fazowych W Procesach Spawania

2015 ◽  
Vol 60 (4) ◽  
pp. 2559-2568 ◽  
Author(s):  
W. Piekarska
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Phase Transformations ◽  
High Speed ◽  
Numerical Models ◽  
Experimental Studies ◽  
Butt Joint ◽  
Heat Of Fusion ◽  
Large Temperature ◽  
Welding Processes

The paper concerns the mathematical and numerical modeling of phase transformations in solid state occurring during welding. The analysis of the influence of heating rate, cooling rate and maximum temperatures of thermal cycles on the kinetics of phase transformations is presented. On the basis of literature data and experimental studies the evaluation of classic mathematical and numerical models of phase transformation is presented with respect to the advanced methods of welding by using a high speed and a high power heat source. The prediction of the structure composition in laser welded butt-joint made of S460 steel is performed, where phase transformations are calculated on the basis of modified numerical models. Temperature distributions are determined as well as the shape and size of fusion zone and heat affected zone (HAZ). Temperature field is obtained by the solution of transient heat transfer equation with convective term and external volumetric heat source taken into account. Latent heat of fusion, evaporation and heats generated during phase transformations in solid state are considered in the numerical algorithm due to the large temperature range present in analyzed process. Results of the numerical prediction of structure composition in HAZ are presented in this work. Obtained results of computer simulations are compared to experimental research performered on the laser welded joint.

scholarly journals THE MAGNETIC PROPERTIES MEASUREMENT OF COIL FOR GRAVITATIONAL ACCELERATION DETERMINATION

2020 ◽  
Vol 5 (2) ◽  
pp. 119-128
Author(s):  
Cherly Salawane ◽  
Supriyadi Supriyadi ◽  
Ronaldo Talapessy ◽  
Mirtha Yunitha Sari Risakotta
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Field Strength ◽  
Electric Current ◽  
Graphical Method ◽  
Current Strength ◽  
Gravitational Acceleration ◽  
The Earth ◽  
The Magnetic Field ◽  
A Current

The value of the gravitational acceleration of the earth above the earth’s surface depends on the position of the latitude and longitude of the earth’s surface, in other words, because the shape of the earth’s surface is not round like a ball. The magnitude of gravity is not the same everywhere on the surface of the earth. The purpose of this study is to analyze the value of the earth’s gravitational acceleration in a laboratory using a current balance with a graphical method. Fluctuations in the value of the magnetic field strength (B) and the value of the electric current strength (i) on the current balance cause the value of laboratory gravitational acceleration (glab) to vary in the transfer of electric charge (q) according to coil type. The magnitude of the earth’s gravitational acceleration value obtained in a laboratory with a current balance for each type of coil is as follows: SF-37 glab-nr=9.89 m/s2, SF-38 glab-nr=9.90 m/s2, SF-39 glab-nr=9.76 m/s2, SF-40 glab-nr=9.95 m/s2, SF-41 glab-nr=9.75 m/s2 dan SF-42 glab-nr=9.93 m/s2. The results obtained indicate that the value of the earth’s gravitational acceleration in a laboratory close to the literature value is the value of the glab-nr in the SF-37 coil type of 9.89 m/s2.

scholarly journals Establishment of the dependence of the strength indicator of the composite material of pressure hoses on the character of single damages

2021 ◽  
Vol 6 (1 (114)) ◽  
pp. 21-27
Author(s):  
Sergii Nazarenko ◽  
Galina Kushnareva ◽  
Natalia Maslich ◽  
Ludmila Knaub ◽  
Nataliia Naumenko ◽  
...  
Keyword(s):  
Field Experiments ◽  
A Priori ◽  
Experimental Studies ◽  
Pressure Head ◽  
Longitudinal Direction ◽  
Experiment Planning ◽  
Emergency Rescue ◽  
Acceptable Model ◽  
Inner Diameter ◽  
Priori Information

Experimental studies are presented and the dependence of the change in the strength of the material of a pressure head fire hose of type T with an inner diameter of 77 mm in the longitudinal direction is established, taking into account single damages. The work describes the plan of the experiment and carried out a number of field experiments to determine the effect of the length ld and the depth K damage on the strength F of the hose material, that is, obtaining the dependence F=f (ld, K). A mathematical method of experiment planning was used and a plan was drawn up for a complete multivariate experiment of type 2k with an acceptable model accuracy of 5 %. The limits of variation of the factors are set taking into account a priori information, experimental capabilities and on the basis of the results of preliminary search experiments. The dependence in the coded and natural values of the factors is obtained. The reliability of the relationship was checked using the Fisher test, the calculated value of which was 5.98, which confirms the adequacy of the described process with a probability of 95 %. Analyzing experimental studies of the dependence of the change in the strength of the hose material on the length and depth of damage, it can be said that the change in the strength of the hose almost linearly depends on the specified damage parameters. It is found that with increasing damage, the strength of the hose material significantly decreases. When varying the length factor and the greatest depth of damage, K=0.4 mm, the strength of the hose material decreases from 11.67 kN to 8.77 kN, and in percentage terms by 25 %. The results obtained can be used in practical units of emergency rescue teams, when diagnosing hidden damage in pressure head fire hoses in order to prevent their failure in case of fires

scholarly journals THE MODEL OF MICROSPHERE GENERATION FROM SILICON DIOXIDE AGGLOMERATES

2018 ◽  
pp. 163-173
Author(s):  
V. V. Shekhovtsov ◽  
O. G. Volokitin ◽  
G. G. Volokitin ◽  
N. K. Skripnikova ◽  
P. V. Balobanov
Keyword(s):  
Phase Transitions ◽  
Silicon Dioxide ◽  
Thermal Plasma ◽  
Quartz Sand ◽  
Total Concentration ◽  
Plasma Heating ◽  
Experimental Studies ◽  
Initial Stage ◽  
Tomsk Region ◽  
Thermochemical Processes

The paper presents the results of theoretical and experimental studies of thermal plasma heating and melting of agglomerated powder based on quartz sand screenings of the Tugan Deposit, Tomsk region, Russia. It is shown that phase transitions significantly affect the process of thermal plasma heating and melting of agglomerated powder, which can lead to unjustified heating of particles. The results of thermochemical processes due to heating are presented herein. It is found that the total concentration of phases subjected to evaporation at the initial stage, is rather small (0.13 wt.%). The model is proposed for the hollow particle formation from silicon dioxide agglomerates.

scholarly journals Effect of electric current on the oil-contaminated soil

2020 ◽  
Vol 61 (2) ◽  
pp. 132-138
Author(s):  
Nikolay S. Shulaev ◽  
Valeriya V. Pryanichnikova ◽  
Ramil R. Kadyrov ◽  
Nikolay A. Bykovsky ◽  
Inna V. Ovsyannikova ◽  
...  
Keyword(s):  
Electric Current ◽  
Contaminated Soils ◽  
Urban Areas ◽  
Experimental Studies ◽  
Good Alternative ◽  
The United States ◽  
Electrochemical Treatment ◽  
Mineral Salts ◽  
Additional Energy ◽  
Cleaning Methods

Electrochemical treatment of contaminated soils is an actual method for the remediation of industrial and urban areas. It represents a good alternative to methods of mechanical, thermal, chemical and biological treatment, and, if necessary, can be used with them. Passing electric current through the soil allows to reduce the concentration of such pollutants as oil and oil products at a considerable depth, to successfully reduce the content of dissolved mineral salts. In recent years a number of works of scientists around the world have been devoted to the study of such technologies. This article discusses the results of experimental studies conducted in the Russian Federation, Romania, Italy, the United States of America and some other countries. A review is given of various options for implementing the electrical treatment of soils contaminated with oil, diesel fuel and oil-containing waste using various types and sizes of electrochemical cells, as well as a variation in the sizes, shapes and materials of the electrodes used (cathodes and anodes). When modeling processes occurring in the soil and induced by electric current, the most significant monitoring parameters are the hydrogen index (soil acidity), amperage and voltage, soil resistance and electrical conductivity, redox potential, and the concentration of pollutants. When assessing the appropriateness of applying electric cleaning methods, the value of energy costs and the efficiency (degree) of cleaning the treated soil are of high importance, therefore, special attention is paid to their analysis. Also the results of author's research in this field are presented in this work. The results of cleaning model soils of various types are considered, mathematical calculations of some of the most important process parameters are given. A specific arrangement of electrodes in wells in vast areas of soil with various concentrations of pollutants is proposed, which allows achieving optimal cleaning results for all areas simultaneously using a single power source without additional energy and, accordingly, material costs.

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