scholarly journals Determination of temperature distribution on windings of oil transformer based on the laws of heat transfer

ScienceRise ◽  
2021 ◽  
pp. 3-13
Author(s):  
Volodymyr Grabko ◽  
Stanislav Tkachenko ◽  
Oleksandr Palaniuk
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Distribution ◽  
Simulation Model ◽  
Power Transformer ◽  
Experimental Studies ◽  
Short Term ◽  
Transformer Winding ◽  
Transformer Equipment ◽  
Technological Product

Object of research: development of a technology for determining the temperature of the winding of a power oil transformer, in particular, the analysis of thermal processes in the winding of a power transformer during short-term overloads, taking into account the influence of the environment. Investigated problem: temperature distribution in the winding of a power oil transformer taking into account short-term load surges in the problem of assessing the residual life of the insulation of the transformer winding by temperature aging. The calculation of the temperature distribution in the winding was carried out using the passport data and characteristics of the power oil transformer, including the winding, transformer oil, load currents. Main scientific results: a mathematical model was calculated, with the help of which the results of temperature distribution in the transformer winding were obtained during short-term load surges or constant work with an increased load. According to the presented model, the analysis of the cooling time of the transformer winding after short-term overloads is carried out. Comparing the results obtained on the simulation model with the known results of experimental studies of the temperature distribution in the winding of a power transformer, the adequacy of the mathematical model is proved. It is shown that the use of the laws of heat transfer in a homogeneous plate to analyze the temperature distribution in the transformer winding is not wrong, but requires clarifications and simplifications. The area of practical use of the research results: enterprises of the machine-building industry and energy companies specializing in the production and operation of transformer equipment. Innovative technological product: simulation model of heat distribution in a transformer winding, which can take into account the load of the transformer, the effect of the environment on the insulation of the transformer windings. An innovative technological product: a method for diagnosing the duration of the non-failure operation of a transformer, which makes it possible to ensure trouble-free operation and save money for the repair of transformer equipment. Scope of application of the innovative technological product: design and development of diagnostic systems for windings of power oil transformers

EXPERIMENTAL STUDIES OF CAR PROPERTIES ON A PHYSICAL MODEL

2019 ◽  
pp. 10-16
Author(s):  
Oleksii Timkov ◽  
Dmytro Yashchenko ◽  
Volodymyr Bosenko
Keyword(s):  
Mathematical Model ◽  
Remote Control ◽  
Physical Model ◽  
Model Experiment ◽  
Experimental Studies ◽  
Electrical Energy ◽  
Short Term ◽  
Motor Current ◽  
Memory Card ◽  
The Mathematical Model

The article deals with the development of a physical model of a car equipped with measuring, recording and remote control equipment for experimental study of car properties. A detailed description of the design of the physical model and of the electronic modules used is given, links to application libraries and the code of the first part of the program for remote control of the model are given. Atmega microcontroller on the Arduino Uno platform was used to manage the model and register the parameters. When moving the car on the memory card saved such parameters as speed, voltage on the motor, current on the motor, the angle of the steered wheel, acceleration along three coordinate axes are recorded. Use of more powerful microcontrollers will allow to expand the list of the registered parameters of movement of the car. It is possible to measure the forces acting on the elements of the car and other parameters. In the future, it is planned to develop a mathematical model of motion of the car and check its adequacy in conducting experimental studies on maneuverability on the physical model. In addition, it is possible to conduct studies of stability and consumption of electrical energy. The physical model allows to quickly change geometric dimensions and mass parameters. In the study of highway trains, this approach will allow to investigate the various layout schemes of highway trains in the short term. It is possible to make two-axle road trains and saddle towed trains, three-way hitched trains of different layout. The results obtained will allow us to improve not only the mathematical model, but also the experimental physical model, and move on to further study the properties of hybrid road trains with an active trailer link. This approach allows to reduce material and time costs when researching the properties of cars and road trains. Keywords: car, physical model, experiment, road trains, sensor, remote control, maneuverability, stability.

Numerical Simulation Model of Electrothermal De-Icing Process on Composite Substrate

2020 ◽  
Author(s):  
Xiaofeng Guo ◽  
Zhiqiang Guo ◽  
Qian Yang ◽  
Wei Dong
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Thermal Properties ◽  
Temperature Distribution ◽  
Simulation Model ◽  
Melting Process ◽  
Ice Melting ◽  
Melted Zone ◽  
Composite Substrate ◽  
Cfrp Composite

Abstract A numerical simulation model of electrothermal de-icing process on carbon fiber reinforced polymer (CFRP) composite is conducted to study the effect of thermal properties of the substrate on the ice melting process. A novel melting model which is based on the enthalpy-porosity method is applied to study the transient ice melting process and heat transfer of the de-icing sys-tem. Multi-layered electrothermal de-icing systems including composites with different fiber orientation are used to analyze the effects of orthotropic heat conductivity of the CFRP composite on the ice melting process and heat transfer. Movement of the ice-water interface, the melted zone thickness and the melted zone area on CFRP composite are investigated on the three-dimensional electrothermal de-icing unit. The effects of thermal properties of substrate on the temperature distribution of the ice-airfoil interface are analyzed. The computational results show that the thermal properties of substrates affect the temperature on the ice-airfoil interface, the temperature distribution in the substrate, ice melting area, ice melting rate and ice melting volume significantly. The time that ice starts to melt on the CFRP composite substrate is earlier than that on the metal substrate. However, it takes more time for the ice to melt completely on the ice-CFRP interface than that on the ice-metal inter-face. The orthotropic heat conductivity of CFRP composite results in strong directivity of the melting area on the ice-CFRP in-terface. A ratio parameter is defined to represent the matching degree of substrate materials and geometry model of de-icing system. The simulation model can be applied to study electrothermal de-icing system of nacelle inlet and airfoil made of composite. The results in present work is also helpful to predict the change of temperature during de-icing process and provide guidelines for the optimizing the electrothermal de-icing system to reduce power consumption according to the fiber structure of composite.

Study on a New Mathematical Model for Aggregate Air Cooling or Heating

2011 ◽  
Vol 374-377 ◽  
pp. 1882-1886
Author(s):  
Li Juan Wang ◽  
Yan Feng Liu ◽  
Jia Ping Liu ◽  
Fei Lu
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Hydraulic Structure ◽  
Surface Heat ◽  
Air Cooling ◽  
Foundation Engineering ◽  
Heating Capacity ◽  
Surface Heat Transfer Coefficient

Before the construction of hydraulic structure, aggregate must be cooled or heated by air (we call it aggregate air cooling or heating in this paper) or other technologies to the required temperature. Previous model of aggregate air cooling or heating cannot provide the center temperature of each aggregate. So a more accurate mathematical model is developed to determine the thermal performance of aggregate, and the surface heat transfer coefficient of wet aggregate is revised. This model can predict the center temperature of an aggregate and can accurately calculate the cold down time or temperature distribution of aggregate, so that the refrigeration or heating capacity can be reasonably supplied. It’s significant for foundation engineering of hydraulic structure.

Mathematical Model for Heat Transfer Simulation of Rotary Alumina Kiln

2013 ◽  
Vol 423-426 ◽  
pp. 881-884
Author(s):  
Xiao Yan Yang ◽  
You Gang Xiao ◽  
Xian Ming Lei
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Distribution ◽  
Phase Change ◽  
Heat Loss ◽  
Chemical Reactions ◽  
Outer Shell ◽  
Test Results ◽  
Distribution Rule ◽  
Heat Transfer Simulation

According to kiln structure and material movement features, considering convective, radioactivity, conductivity and various phase change and chemical reactions, a series of comprehensive models are built for quantifying the thermal fluxes from the gas to the material bed and the heat loss from outer shell to the atmosphere in the rotary alumina kiln. The results show that the temperatures of outer shell accord with test results; the temperature distribution rule of gas is the same with that of materials, but the gas temperatures are higher; it is feasible to use the model to improve alumina kiln performance.

scholarly journals Mathematical model of heat transfer in roll caliber

2019 ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Heat Equation ◽  
Rolling Mill ◽  
Thermal Process ◽  
Stationary Heat

A physical model of the thermal process in the roll caliber during the rolling of the tape on a two-roll rolling mill was constructed. A mathematical model of the temperature field of a rolling hollow roll of a rolling state of a cylindrical shape rotating about its axis with constant angular velocity is proposed. The mathematical model takes into account different conditions of heat exchange of the inner and outer surfaces of the roll with the belt and its surrounding environment. The temperature field of a hollow roll of a rolling mill is considered as an initial boundary-value problem for a homogeneous non-stationary heat equation with inhomogeneous, nonlinear boundary conditions, which also depend on the angle of rotation of the roll around its axis. The equation describes the temperature field of the rolls during uncontrolled heat transfer during rolling. It significantly depends on the time and number of revolutions around its axis. With a large number of revolutions of the roll around its axis, a quasi-stationary temperature distribution occurs. Therefore, the simplified problem of determining a quasistationary temperature field, which is associated with a thermal process that is time-independent, is considered further in the work. In this case, the temperature field is described using the boundary value problem in a ring for a homogeneous stationary heat equation with inhomogeneous boundary conditions and heat transfer conditions outside the ring, which lie from the angular coordinate. After the averaging operation, the solution of this problem is reduced to solving the equivalent integral equation of Hammerstein type with a kernel in the form of the Green's function. The Mathcad computer mathematical system builds the temperature distribution of the roll surface. An algorithm for solving a inhomogeneous problem was developed and the temperature distribution of the roll was constructed.

scholarly journals Mathematical Models and Algorithms of Optimal Load Management of Electricity Consumers

2019 ◽  
Vol 62 (6) ◽  
pp. 528-535 ◽  
Author(s):  
I. U. Rakhmonov ◽  
K. M. Reymov
Keyword(s):  
Mathematical Model ◽  
Power Systems ◽  
Power System ◽  
Experimental Studies ◽  
Optimal Planning ◽  
Short Term ◽  
Planning Period ◽  
Efficient Operation ◽  
Load Profile ◽  
Optimal Load

Load profile alignment based on optimal power consumption management is considered to be one of the main ways to ensure efficient operation of energy systems in the short-term planning. Alignment load profile with a view to reducing costs can be implemented with the aid of consumers’ involvement by administrative and economic measures. Administrative measures are associated with the forced restriction of consumer loads in certain intervals of the planning period. On one hand, these measures provide benefits to the power system by alignment load profile, and on the other hand, they cause detriment to consumers. Ultimately, in some cases, for the whole power system, the detriment may be greater than the benefits. Therefore, it is advisable to use administrative measures in conditions of shortage of power and electricity in the power system. Optimal planning of short-term regimes of power systems according to rigid load profile received after alignment can be carried out by traditional methods. The solution of such a problem ought to be initially carried out under conditions of non-rigid load profile resulting from the directive use of administrative and economic measures carried out with the help of specially developed models. In this regard, the paper proposes a mathematical model of the problem of optimizing load profile of regulated electricity consumers to be used for optimal planning of shortterm power system modes, an algorithm for optimal planning of a short-term power system mode with optimizing load profile of regulated power consumers. Also, algorithms are proposed for accounting for simple and functional constraints in the form of equalities and inequalities when optimizing load profile. The effectiveness of the described algorithm for optimizing the short-term mode of the power system, taking into account the optimal load control of adjustable electricity consumers, has been studied using the example of optimal coverage of the load profile of power system, which contains two consumers with adjustable load profile, and two TPPs. Based on the calculated-and-experimental studies, it was determined that the proposed mathematical model of the problem is adequate, while the developed algorithms for optimal planning of short-term power system modes with optimization of load profile of regulated electricity consumers and taking into account various types of limitations are of high computational qualities.

scholarly journals Cooling Caramel in Ethyl Alcohol: Constructing a Mathematical Model

2020 ◽  
Vol 50 (3) ◽  
pp. 425-438
Author(s):  
Anatoly Khvostov ◽  
Gazibeg Magomedov ◽  
Viktor Ryazhskikh ◽  
Inessa Plotnikova ◽  
Aleksey Zhuravlev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
High Performance ◽  
Experimental Studies ◽  
Transient Heat Conduction ◽  
Flow Speed ◽  
Model Parameters ◽  
Air Cooling ◽  
Radial Temperature ◽  
Cooling Period

Introduction. The process of air-cooling caramel remains one of the most complicated issues of contemporary food industry, since it is time-consuming and requires multi-level cooling units. Therefore, the development of an innovative method of cooling caramel in “cold” potable ethanol is an urgent task the modern food science has to solve. The method op-timizes and intensifies the technological process, as it reduces production areas by eliminating some technological stages and complex units of metal-intensive and energyintensive equipment. It gives caramel antiseptic properties and a perfectly smooth, shiny, and dry surface. Study objects and methods. The research objective was to develop a fundamentally new and promising caramel technology. The experimental studies on the production and cooling were performed in a mixing and forming multi-unit with a high-performance cooling chamber. The chamber had functions of automatic measurements and control of the main parameters of the cooling process. The research used “cold” potable ethanol. Results and discussion. The paper introduces a mathematical model of the process of cooling caramel in ethanol. It includes heat transfer processes in alcohol, in the caramel mass, and on their border. The model was based on equations of transient heat conduction in a sphere. The process of heat exchange with the environment, i.e. alcohol, was characterized by the coefficient of heat transfer from the sphere. The model parameters included dynamic viscosity, density, thermal conductivity coefficient, and specific heat capacity. Based on the experimental data, the parameters were ap-proximated as a function of temperature by a cubic polynomial. Conclusion. The developed mathematical model made it possible to estimate the radial temperature distribution of caramel in the form of a sphere during its convective cooling in ethanol. The model also predicted the change in the average volume temperature of the caramel and energy costs depending on the cooling period, the flow speed of the ethanol, the thermophysical properties of the caramel and the cooling agent. The proposed mathematical model can be used to calculate the required consumption of ethanol for cooling and backwater of the caramel production line.

scholarly journals Modeling of the heat transfer process in an air heat pump fanless evaporator

2018 ◽  
Vol 240 ◽  
pp. 05012
Author(s):  
Piotr Kopeć ◽  
Beata Niezgoda-Żelasko
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Mixed Convection ◽  
Heat Pump ◽  
Transfer Process ◽  
Experimental Studies ◽  
Heat Transfer Process ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

This paper analyses the mixed convection process in a fanless evaporator of an air heat pump. The text of the paper shows the authors’ experimental studies results of the temperature distribution and the local values of heat transfer coefficients on the outer surface of vertical tubes with longitudinal fins for the case of mixed convection and fins of a specific shape of their cross-section (prismatic, wavy fins). The experimental studies include the air velocities wa=2,3 m/s and the temperature differences between air and the refrigerant inside the heat exchanger tubes which is ΔT=24-40K. The results obtained were used for verification of CFD modeling of the heat transfer process for the discussed case of heat transfer and the geometry of the finned surface. The numerical analysis was performed for: the temperature distribution along the fin height, the tube perimeter and height, the distribution of local heat transfer coefficients on the finned tube perimeter and along its height. The simulated calculations were used to verify the method of determination of fin efficiency.

Assessing the feasibility of using a carbon material in the design of a radiative cooler for spacecraft

2020 ◽  
pp. 42-47
Author(s):  
Aleksandr P. BELOGLAZOV ◽  
Andrey G. EREMIN ◽  
Sergey A. NEMYKIN ◽  
Aleksey Yu ZHURAVLEV
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Key Words ◽  
Heat Pipe ◽  
Carbon Material ◽  
Manufacturing Process ◽  
Experimental Studies ◽  
Feasibility Studies ◽  
Braze Joint ◽  
Design And Manufacturing

The paper discusses the results of feasibility studies for using a carbon web as the radiating surface of a spacecraft radiative cooler. It proposes a design and manufacturing process solution that provides for a link between heat-transfer devices and the carbon web that has the necessary strength and minimizes heat loss. It presents results of experimental studies of temperature distribution across the radiative surface of the carbon web with mockups of the heat transfer devices. An analysis of the obtained results showed that the use of a carbon web in the design of a spacecraft radiative cooler is both feasible and promising. Key words: spacecraft, heat-conductive carbon web, radiative cooler, heat pipe, braze joint, heater.

Heat Transfer under a Flow of the Highly Viscous Crude Oil in a Buried Oil Pipeline

2021 ◽  
Vol 107 ◽  
pp. 122-128
Author(s):  
Aidar Kadyirov ◽  
Julia Karaeva ◽  
Ekaterina Vachagina
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Distribution ◽  
Crude Oil ◽  
Air Temperature ◽  
High Viscosity ◽  
Numerical Calculations ◽  
Oil Pipeline ◽  
Transfer Processes ◽  
The Republic

The paper presents a mathematical model and the results of numerical calculations of heat transfer processes during the flow of highly viscous crude oil in an oil pipeline. Comparison with literature data is performed. The samples of oil from the field of the Republic of Tatarstan (Russia) that are characterized by high viscosity were considered as crude oil. The influence of air temperature on the temperature distribution in the soil was investigated. The analysis of the distribution of crude oil temperature along the length of the pipeline was carried out.

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