Determination Of Temperature Field Research Articles

Modeling of Thermal Processes in DED Using SolidWorks Simulation

The study analyzes software products for numerical modeling of additive processes performed using SLM and DED technologies. Determining temperature fields in DMD processes is an important and complex task. Based on previously determined experimental data on the volume of molten material added during cladding, the thermal processes during laser cladding of powder materials were modeled in the SolidWorks system. This allowed determining the distribution of temperature fields on the substrate and in the cladded material over time.

Mathematical models for determining and analyzing thermal regimes in mining industry mechanism structures

Purpose. To develop linear and nonlinear mathematical models of heat conduction for isotropic heterogeneous media with internal heating. This will allow for an increased accuracy in determining temperature fields, which will subsequently impact the effectiveness of designing mechanisms, devices, and individual components of structures that have a layered structure and are subjected to heat stress. Methodology. For the development of linear and nonlinear mathematical models of the temperature field and the analysis of temperature regimes in layered media with internal thermal heating, the coefficient of thermal conductivity is described as a whole using asymmetric unit functions. This makes it possible to solve a differential equation with singular coefficients in both linear and nonlinear boundary value problems of heat conduction with appropriate boundary conditions. Findings. Quadratic equations are obtained to determine the analytical solutions of linear and nonlinear boundary problems of heat conduction for a layered plate with internal heat load. Originality. The scientific novelty lies in the given method of linearization of the nonlinear mathematical model of heat conduction and obtaining analytical solutions, in a closed form, of the corresponding linear and nonlinear boundary value problems for isotropic layered media subjected to internal heating. Practical value. The developed linear and nonlinear mathematical models for determining the temperature distribution in layered structures with internal heating make it possible to analyze heat exchange processes and ensure the thermal stability of such structures. This also makes it possible to increase the heat resistance of structures and protect them from overheating, which can lead to damage to individual components and elements of mechanisms, as well as to the entire structure as a whole. The resulting analytical solutions can be used to predict temperature fields in mine shafts, underground environments and mechanisms of mining equipment, in particular, in drilling and underground compressor stations, ventilation systems and other equipment, which improves work efficiency and reduces useful energy consumption.

Statement of the problem modeling the process vacuum microwave drying for determining temperature fields in foamed suspensions

Objective. The aim of the study is to formulate a mathematical model of the process of vacuum microwave drying to determine the temperature fields in foamed suspensions. With the obvious advantages of microwave drying in a vacuum, the possibility of overheating of the dried material is not excluded, which affects its quality. Therefore, the limitation on the temperature of the material during drying must be taken into account in the simulation.Method. The study is based on the methods of simulation computer modeling.Result. The formulation of the modeling problem for determining the temperature fields in foamed suspensions in a wide range of regime parameters is proposed.Conclusion. Increasing the accuracy of simulation results by improving the mathematical description is the basis of modern research in the field of technology and equipment for vacuum microwave drying.

Determination of temperature fields and stresses during the construction of a massive monolithic foundation slab of a wind turbine tower

The article proposes a method for determining temperature fields and stresses during the construction of massive monolithic structures in a two-dimensional axisymmetric formulation. The solution is performed using the finite element method. The calculation takes into account the shrinkage of concrete, as well as the change in its physical and mechanical characteristics over time. The problem of calculating a massive monolithic foundation of a wind turbine is presented. Recommendations are given to reduce the risk of early cracking.

STRESS-STRAIN STATE OF REINFORCED CONCRETE PIPES UNDER THE INFLUENCE OF CLIMATIC TEMPERATURE CHANGES IN THE ENVIRONMENT

The research analysis on determining temperature fields, stresses and deformations of transport structures under the influence of variable climatic temperature changes in the environment is carried out. It is established that climatic temperature changes in the environment cause the occurrence of temperature stresses and deformations of transport structures. The main damages and defects of reinforced concrete pipes in operation are given. It is established that one of the causes of defects and damages to reinforced concrete pipes is the level of temperature stresses and deformations that occur in the contact of a metal structure with a reinforced concrete pipe due to the action of variable temperatures caused by climatic temperature changes in the environment. A finite element model is developed for estimating the temperature fields and stresses of reinforced concrete pipes reinforced with metal corrugated structures, taking into account the action of variable climatic temperatures of the environment. The distribution of temperature fields in the transverse and longitudinal directions of reinforced concrete pipe under the action of positive ambient temperatures is calculated. It is established that the temperature field will be unevenly distributed over the pipe surface. In the transverse direction of the pipe, a temperature difference of +10° C was recorded between the reinforced concrete and metal shells. The calculation of temperature stresses and deformations of the pipe under the action of positive ambient temperatures is performed. It is established that the maximum value of normal stresses occurs at the contact of a metal pipe with a reinforced concrete one. At the same time, the value of temperature stresses in the transverse direction of the pipe is 321.61 kPa, in the longitudinal direction it is 321.61 kPa and in the vertical direction, it is 253.84 kPa. It is established that improving the theory and practice of determining the impact of climatic temperature changes on reinforced concrete pipes in the future will allow using appropriate materials and methods to strengthen these structures that meet the real conditions of pipe in operation, which will cause an increase in the service life of these structures in operation.

Similarity solution of two-phase cylindrical Stefan solidification problem

The mathematical model of determining temperature fields in cylindrical domain with solidification process is represented. The solidification process of cylinder due to cooling is constructed by two-phase cylindrical Stefan problem for liquid and solid zones with freezing interface. Respect to strength of the heat sink at the center of cylindrical material boundary condition  is an important to determine temperature in solid domain. The analytical solution of the problem is introduced with method of similarity principle which enables us to reduce free boundary problem to ordinary differential equations. Temperature solutions of solid and liquid zones are represented by special function which called exponential integral equation. The free boundary at freezing interface and temperatures at two phases are determined. Lemmas about exponential integral functions are introduced and used to prove that obtained operator function is contraction operator. Upper boundness of the exponential integral function is checked graphically. It is shown that existence of uniqueness of solution exists.

Comprehensive Thermodynamic Analysis of Steam Storage in a Steam Cycle in a Different Regime of Work: A Zero-Dimensional and Three-Dimensional Approach

Abstract Due to the current trends aiming to reduce carbon dioxide emissions by increasing the use of renewable energy sources, changes are required in the operation of coal-fired steam units. The unstable nature of renewable energy sources, depending on weather conditions, means that the amount of energy produced varies and is not always in line with peak demand. To ensure the security and stability of energy supplies in the energy system, renewable sources should cooperate with units independent of environmental conditions. With conventional steam systems, the main issue of such energy storage applied to steam turbine units is presented in this article, which, in the event of a need for a sudden reduction of the system load, prevents overloading of the boiler and turbines, improving the safety of the system. This article presents a thermodynamic model of this energy storage. A zero-dimensional (0D) model was implemented, including the operating parameters of the unit. This model directly relates to the thermodynamic parameters defined at specific points of the thermodynamic cycle. Based on the 0D model, it was shown that the process of loading the energy storage with steam leads to a load reduction of up to 4%. Conversely, when discharging the stored energy, the net power of the steam block may increase by 0.4%. For more detailed analysis, a three-dimensional (3D) nonequilibrium with including cross effects approach was applied. This approach is based on flow models, with phase transitions that determine temperature fields, densities, and phase transition in relevant space, and is used for more accurate analysis. Here, we investigate the relationship between the 0D and 3D approaches in the context of steam storage. The combination of these two approaches is the fundamental novelty of this article.

Determining Temperature Fields in a Spatially Inhomogeneous Nonlinear Medium

We propose a method of determining temperature fields in a spatially inhomogeneous medium with temperature-dependent thermophysical properties of the material. For this purpose, point and nonlocal transformations of the nonstationary heat conduction equation are used. Examples of applying the theory for various boundary conditions in the spherical symmetric case are given.

Experimental Study of the Distribution of Temperature Fields in the Butt Contour of a Welded Joint Made of Carbon and High-Alloy Structural Steels

A graphic-analytical method for determining temperature fields in the butt contour of a welded joint of a thin-walled tube with a base is presented. The method is based on the experimental data of temperature measurement at the reference points of the structure. The features of the elements of the welded joint made of carbon and high-alloy structural steels and the modes of electric arc welding were taken into account. A graphic-analytical method for determining temperature fields is proposed, which, on the basis of the theory of welding strains and stresses, makes it possible to determine temperature stresses and strains, both in the elements of the joint and in the contour of the weld.

Stressed state of striker – bimetall system at production of three-layer steel bimetallic strips in the unit of continuous casting and deformation

The article presents the initial data for calculation of stress-strain state of a three-layer bimetallic strip. The regularities of distribution of axial and tangent stresses in the zone of cyclic deformation are considered. The main loads acting on the mold strikers are described for the unit of combined continuous casting and deformation at production of steel three-layer bimetallic strips. The authors describe the method for determining total stresses in the installation strikers from the efforts of compression and temperature loads. Also temperature boundary conditions for determining the temperature fields are considered. The procedure for determining temperature fields and thermoelastic stresses in the strikers is shown using the ANSYS package. The calculation results of temperature fields and thermoelastic stresses were made in five sections of the striker and are given for characteristic lines. The nature of temperature distribution over the thickness of the striker is shown when it is cooled with water at idling and in contact with a bimetallic ingot during its compression. For the calculated temperature fields, the authors have determined the axial and equivalent stresses occurring in the strikers without channels when the ingot is compressed and cooled with water during idling. The magnitudes and patterns of distribution of total axial stresses from the compression and thermal loads are also given along the thickness of the contact layer, along the height and thickness of the strikers.

ЭЛЕКТРОМАГНИТНАЯ СУШКА ВЛАЖНЫХ МАТЕРИАЛОВ С МАЛОЙ ГЛУБИНОЙ ПРОНИКНОВЕНИЯ СВЧ-ИЗЛУЧЕНИЯ В УСЛОВИЯХ ТЕПЛОСБРОСА РАДИАЦИЕЙ И КОНВЕКЦИЕЙ. III. СТАДИЯ ПАДАЮЩЕЙ СКОРОСТИ СУШКИ

Актуальность исследованияпродиктована необходимостью разработки математических моделей СВЧ-нагрева и МВ-сушки влажных материалов для получения технологически оптимальных и экономически выгодных режимов. Настоящая публикация является продолжением статей тех же авторов в «Известия Томского политехнического университета. Инжиниринг георесурсов», в которой с помощью математического моделирования подробно был изучен процесс на первой и второй стадиях сушки – стадии прогрева, когда теплообмен между поверхностью влажного тела и окружающей средой осуществляется за счет радиации и конвекции, а СВЧ-энергия поглощается поверхностным слоем из-за малой её глубины проникновения, а также стадии постоянной скорости сушки. Построены асимптотические решения этой нелинейной задачи для малых и больших значений безразмерного времени, востребованные инженерной практикой, как для параметрического анализа, так и для проведения оперативных расчетов. Подход, связанный с рассмотрением третьей стадии – стадии падающей скорости сушки, основан на установлении базового уравнения сушки, которое обеспечивает взаимосвязь между теплообменом и влагообменом с помощью критерия Ребиндера. Цель: постановка задачитретьего этапа СВЧ-сушки влажного материала – этапа падающей скорости сушки– и реализация теоретического решения по определению распределения температурного поля по толщине слоя ивеличины скорости сушки. Объектом исследования является плоский слойвлажного материала – уголь, песок,древесина и др. капиллярно-пористые массивы, на которые воздействует СВЧ-излучение. Такие материалы обладают высокой диэлектрической проницаемостью и как следствие весьма эффективно поглощают СВЧ-излучение, которое почти на 100 % преобразуется в тепловую энергию. Методы исследованиясвязаны с математическим моделированием, в основе которых лежат уравнения электродинамики Максвелла и тепловлагопереноса А.В. Лыкова. В данной статье при оценке параметров тепловлагопереноса учет теплообмена ведется более детально, нежели массообмена. Также одной из особенностей данной задачи электромагнитной сушкиявляется рассмотрение материалов с малой глубиной поглощения, в силу чего в системе уравнений для нагрева источниковый член находится в граничном условии. В результате исследованийбыли определены температура и влагосодержание подсушиваемого тела в режиме падающей скорости сушки, получены расчетные соотношения аналитического характера для малых и больших параметров времени.

Using Planar Laser Induced Fluorescence to determine temperature fields of drops, films, and aerosols

By using thermocouples and Planar Laser-Induced Fluorescence (PLIF) method, the temperature fields of droplets, films, and aerosols of water have been measured at different heating schemes. Among them were the droplet immersion into a high-temperature gaseous area with the help of holders, lowering of the droplets on a heated substrate as well as their heating at free fall through air. The environment temperature varied from 20 °C to 800 °C. The Rhodamine B dye has been applied as a fluorophore. The effect of the bubbles nucleation in a droplet and the position of a light sheet on the PLIF measurements has been found out. The study described conditions for the emergence of “dead zones” in the temperature field, in which temperature was not able to be measured. At a fluorophore concentration of less than 2000 μg/l, a difference between luminosities of droplets, films, and aerosols did not exceed 3%.

Determining 2D temperature field in flow boiling with the use of Trefftz functions

The paper proposes the use of Trefftz method to solve the triple coupled heat conduction problem in flow boiling of refrigerant in an asymmetrically heated minichannel. A mathematical model of heat transfer in a rectangular minichannel is suggested. Two sets of Trefftz functions were used to determine 2D temperature fields at a fluid flow in the minichannel tilted at a known angle. The procedure for the calculation of the liquid temperature was coupled with the process of determining temperature fields in two adjacent elements of the experimental stand with the minichannel, i.e. in the glass pane and the heating foil. Heat transfer in the glass, foil and liquid is described using various 2D differential equations with an adequate set of boundary conditions. Solving those equations led to the solving of the triple coupled heat conduction problem made up of one direct and two subsequent inverse problems. The results are presented as: (1) 2D temperature of the glass pane, the heating foil, the flowing liquid, (2) mean square errors between temperature approximations and selected boundary conditions, (3) the heat transfer coefficient versus the distance from the minichannel inlet.

Thermo-mechanical loads on a spacecraft in low Earth orbits

The present paper develops model for evaluating the results of high energy micro-particle space debris irradiation of space structures. The closed form solution formulas for determining temperature fields, thermomechanical failure are presented. Fracture of brittle materials under local heat exposure is studied.

Investigation of the Effect of the Non-uniform Flow Distribution After Compressor of Gas Turbine Engine on Inlet Parameters of the Turbine

The position of combustion chamber between compressor and turbine and combined action of these elements imply that the working processes of all these elements are interconnected. One of the main requirements of the combustion chamber is the formation of the desirable temperature field at the turbine inlet, which can realize necessary durability of nozzle assembly and blade wheel of the first stage of high-pressure turbine. The method of integrated simulation of combustion chamber and neighboring nodes (compressor and turbine) was developed. On the first stage of the study, this method was used to investigate the influence of non-uniformity of flow distribution, occurred after compressor blades on combustion chamber workflow. The goal of the study is to assess the impact of non-uniformity of flow distribution after the compressor on the parameters before the turbine. The calculation was carried out in a transient case for some operation mode of the engine. The simulation showed that the inclusion of compressor has an effect on combustion chamber workflow and allows us to determine temperature field at the turbine inlet and assesses its durability more accurately. In addition, the simulation with turbine showed the changes in flow velocity distribution and pressure in combustion chamber.

Method of lines in nonlinear frictional heating during braking

The boundary-value heat conduction problem for two semi-infinite bodies compressed by constant pressure and sliding with a constant deceleration has been formulated. Due to friction at the contact surface the heat is generated. It is assumed that the materials of the bodies are thermal sensitive, i.e. their thermophysical properties are temperature dependent. This problem allows determining temperature fields in such elements of brakes, as a pad and a disk. At the first stage, the Kirchhoff transformation has been used for partial linearization of the nonlinear problem. Next, the Kirchhoff functions have been found by the method of lines. The transition has been made from the Kirchhoff functions to temperatures on the basis of formulas obtained for the friction couple aluminum alloy series (a disk) — the metal-ceramic (a pad). For the case of braking with a constant deceleration and at constant pressure the comparison of the results obtained with the proposed approach, and on the basis of an iterative procedure has been executed. The influence of duration of pressure increase on the temperature has been investigated.

Heat exchange between non-insulated barn and the ground in experimental research

The paper presents the results of two-year studies conducted in real operating conditions of a non-insulated and unheated barn for 120 cows. As a result, it was possible to determine temperature fields in the ground beneath the floor and around the building, as well as to define heat flux directions. It was concluded that there is no analogy between temperature fields and heat flux directions with the heated buildings. In colder periods of the year, the heat accumulated in the ground is emitted to the inside of the building; in the summer, the ground absorbs the excess of heat from the building. The final conclusion was that the foundations should be insulated vertically.

Effect of forming factors on surface temperature and residual deformation of the plate in line heating

Parameters of line heating input are key factors which determine temperature field and deformation field in line heating for ship hull plate manufacturing. Two coupling variables named as qs (average energy input per unit area), qs·t (average energy input per unit area and time) are constructed with line heating input parameters to describe relations between final deformation of plate and acetylene flux, heating velocity, heat source radius, heat source efficiency, and length of heating line in line heating. The relation between the new variables and residual deformation is revealed via numerical simulation. The results show that the new variables can reflect the relation between heating parameters and final residual deformation.

BEARING CAPACITY OF AXIALLY LOADED TIMBER MEMBERS – ESTIMATION UNDER UNEVEN FIRE ACTION / MEDINIŲ CENTRIŠKAI GNIUŽDOMŲ ELEMENTŲ, NETOLYGIAI VEIKIAMŲ UGNIES LAIKOMOSIOS GALIOS, SKAIČIAVIMAS

The article deals with the peculiarities of calculating bearing capacity for axially loaded timber members under uneven fire action. According to LST EN 1995-1-2 and finite element modelling for determining temperature fields and variations in timber strength under elevated temperature, the method of simple calculations was applied. Calculations are based on the data and results of experimental investigations into the resistance of axially loaded members to fire. Data on variations in timber strength were obtained conducting laboratory tests using the specimens of Lithuanian pine under elevated temperature. Santrauka Atliekant šį tyrimą išnagrinėti netolygiai gaisro veikiamų neapsaugotų liaunų medinių centriškai gniuždomų elementų laikomosios galios skaičiavimo ypatumai, taikant paprastuosius skaičiavimo metodus, pateiktus LST EN 1995-1-2, ir naudojant baigtinių elementų programa nustatytus elemento skerspjūvio temperatūrinius laukus medienos stiprių pokyčiams įvertinti. Skaičiavimo duomenys grindžiami atliktais eksperimentiniais liaunų medinių centriškai gniuždomų strypų atsparumo ugniai tyrimo duomenimis ir rezultatais. Medienos stiprių pokyčiai, naudojami skaičiuojant, paimti remiantis Lietuvoje augančios pušiės medienos stiprių pokyčių bandymo rezultatais.

Heat Transfer Reduction due to a Ceiling-Mounted Barrier in an Enclosure with Natural Convection

Effects of a ceiling-mounted barrier on natural convection heat transfer in a square cavity with differentially heated wall are numerically investigated. A limit case, in which the partition has small thickness and low thermal conductivity, is studied. The study is performed for nine different locations of barrier on the ceiling, two different lengths of barrier as 15 and 50% of the side wall, and Rayleigh numbers from 103 to 106. The vorticity and streamfunction approach is used to obtain velocity distribution, and the energy equation is solved to determine temperature field in the cavity. The variations of the local Nusselt number on the hot and cold walls and the change of mean Nusselt number with the location of barrier in the cavities with different Rayleigh numbers are presented. The obtained results show that a wall-mounted barrier can be used to reduce heat transfer rate through the cavity; however, its effectiveness depends on length and location of barrier and Rayleigh number.