Nonstationary Temperature Research Articles

Risk decreasing of water waste through spontaneous fracturing in injectors by integrated well-testing and production logging

Background. When creating an effective reservoir pressure maintenance system, unstable spontaneous hydraulic fractures can be created in injection wells. This can both negatively and positively affect hydrocarbon production. First, fracture improves reservoir connectivity, which increases injection efficiency. On the other hand, unstable fractures can cause behind-the-casing flows and unproductive injection into off-target layers or fingering. 
 
 Goal. The paper is devoted to the analysis of well testing (PTA) and production logging (PLT) improvement for the diagnosis of unstable fractures in injection wells. 
 
 Materials and methods. The analysis is based on the results of modeling the pressure in the reservoir system, describing the penetration reservoirs by an unrestricted conductivity unstable fracture. It is taken into account that the fracture can cross both the perforated formation and the thickness not penetrated by the perforation, and can grow with increasing overbalance. 
 
 The modeling results made it possible both to assess the potential informative capabilities of well testing and to substantiate recommendations for the practical use of the obtained results. 
 
 Conclusions. The proposed approaches to the technology of well testing and production logging and the interpretation of their results make it possible to estimate the additional thicknesses of the reservoirs connected by the spontaneous hydraulic fracturing to injection, the proportion of nonproductive injection in the total volume of the well. The research technology used by the authors is based on continuous measurements of pressure and flow rate during cyclic change of pressure and assessment of the effective transmissibility of the formation system at different heights of unstable fractures. 
 
 The role of the PLT is to determine the effective production thickness of the reservoirs. When assessing the injectivity profile when penetrating the injector with the spontaneous hydraulic fracturing, the key role belongs to non-stationary temperature logging. In this case, it is necessary to take into account the specific features of temperature relaxation in the wellbore after the injection cycle, related to hydraulic fracturing, primarily the increase in the relaxation rate with increasing fracture length.

Исследование напряженно-деформированного и температурного состояния режущей части инструмента с использованием лазерной интерферометрии

Introduction. The efficiency of the metalworking processes highly depends on the performance of the implemented cutting tools that can be increased by studying its stress-strain state and temperature fields. Existing stress analysis methods either have a low accuracy or are inapplicable for research during the operation of the tools made of materials with high mechanical properties. In addition, the study of temperature fields using known methods is difficult due to the small size of the cutting zone, high temperatures, and a heavy temperature gradient appearing during metal cutting. The purpose of this study is to develop new experimental methods for measuring the stress-strain and temperature fields in the cutting tool during its operation using laser interferometry. The methods include: obtaining interference fringe patterns using an interferometer with the original design, obtaining the tool deformation field during the cutting process by recording the changes in interference fringe patterns using a high-speed camera, processing fringe patterns with the separation of deformations caused by heating and cutting forces, and calculating temperature fields and stress distributions using mechanical properties and the coefficient of thermal expansion of the tool material. The advantages of the developed methods include: applicability under real operating conditions of the cutting tool, ability to study the non-stationary stress-strain state and temperatures during an operation, and achievement of a high spatial resolution and a small field of view for the investigated surface. Results and Discussion. The experimental study confirmed the efficiency of the methods. The results of the study included the fields of stresses and temperatures obtained during the orthogonal cutting of heat-resistant steel with a tool made of cemented tungsten carbide WC-8Co. The developed methods can be used to study the cutting tool efficiency at close to real conditions and in obtaining boundary conditions for the study stress-strain state of a workpiece material near the cutting zone.

Semiconductor metal oxide sensor for hydrogen sulphide operating under non-stationary temperature conditions

The aim of the work was to create a selective gas sensor for hydrogen sulphide. As a result of adding ammonia to the zinc acetate solution, centrifuging the obtained zinc hydroxide and subsequent calcination, a polydisperse zinc oxide powder with a grain size of 5–50 nm was obtained. The material was characterized using X-ray phase analysis and transmission electron microscopy. Subsequently, silver nitrate and terpeniol were added to the zinc oxide nanopowder to form a paste. The gas-sensitive material was obtained by applying the resulting paste on a special dielectric substrate and subsequent calcination, as a result of which the terpeniol burned out, and the silver nitrate turned into an oxide (the mass fraction of the silver was 3%). A non-stationary temperature mode for the operation of the sensor was selected, in which, after rapidheating of the sensor to 450 °C (2 seconds), slow (13 seconds) cooling to 100 °C occurred. Each subsequent heating-cooling cycle with a total period of 15 seconds began immediately after the end of the previous cycle. The use of an unsteady temperature mode in combination with the selection of the composition of the gas-sensitive layer made it possible to obtain a response of 200 for a hydrogen sulphide concentration of 1 ppm. Along with an increase in sensitivity, a significant increase in selectivity was also observed. The cross-sensitivity for the determination of hydrogen sulphide and other reducing gases (CO, NH3, H2) was more than three orders of magnitude. Thus, this sensor can be used to detect hydrogen sulphide even in the presence of interfering components. The use of highly selective sensors in the tasks of qualitative andquantitative analysis can significantly simplify the calibration in comparison with “electronic nose” devices. Devices based on highly selective sensors do not require the use of mathematical methods for processing multidimensional data arrays.

Studies on the impact of external fire on the lye of the shelter housing

Purpose: The presented article presents a numerical analysis carried out to determine the impact of an external fire taking place on the surface of the ground on the level of stress of the trench shelter casing protected by a layer of soil. Design/methodology/approach: Numerical analysis was carried out in two stages. In the first stage, a quasi-stationary distribution of the initial temperature in the centre of the ground and the shelter casing was sought. In the second stage of the analysis, the effect of the fire was considered according to the profile of time changes in the temperature of the shelter object. Findings: We assume that the trench shelter is in an oblong shape, and the fire extends over a vast area. The area surrounding the shelter casing was treated as a material with average constant thermodynamic values. Research limitations/implications: The process related to heating and cooling the enclosure was described on the basis of the Fourier equation on heat conduction in terms of the heterogeneous nature of the material, primer and concrete. Practical implications: The use of the trench shelter model as a research element in the design of special objects. Originality/value: The methods of non-stationary temperature flow through the ground and the shelter casing used, allows for a very realistic indication of how the housing will behave under the influence of high temperature caused by an external fire. The article can be useful for designers who design underground shelters.

Daily maximum temperature forecasting in changing climate using a hybrid of Multi-dimensional Complementary Ensemble Empirical Mode Decomposition and Radial Basis Function Neural Network

Study regionMetropolitan Taipei city, Taiwan. Study focusThe severity of climate change in Taiwan is increasing, and the average temperature in Taiwan has increased by 1.0–1.4 °C over the last century, which is higher than the global average. A state-of-the-art hybrid of Multi-dimensional Complementary Ensemble Empirical Mode Decomposition (MCEEMD) and Radial Basis Function Neural Network (RBFNN) is developed for the analysis, simulation, and forecasting of extreme temperature events. The MCEEMD is first introduced to process non-stationary, nonlinear gridded climate data from 1960 to 2017. The RBFNN model is then coupled with the MCEEMD algorithm to forecast the 7-day daily maximum temperatures in Taipei. New hydrological insights for the regionLong-term time series data such as temperature exhibit non-stationarity, and non-linearity, thus making it more challenging to assessing the future trend and variability. It is shown that for daily maximum temperatures in Taipei, changes in extremes are more pronounced and impactful than changes in the mean values in response to global warming. The newly developed hybrid MCEEMD-RBFNN model is capable of analyzing the nonstationary and nonlinear daily maximum temperature data, and then forecasting the daily maximum temperature over the next 7 days. Short-term trends and variability of daily maximum temperature in Taipei can thus be identified and diagnosed for hazard prevention and risk assessment of heatwave events.

Прогнозирование ожоговых травм при испытаниях специальной защитной одежды пожарных на стенде «Термоманекен»

Ensuring safety of the personnel when exposed to thermal factors of a fire, including through the use of various types of special protective clothing, is an important component of the firefighter occupational safety. Quality control of special protective clothing of the firefighters takes place in several stages. The final stage is to conduct tests on the Thermomanequin test bench when the workwear is in the working position on a full-size manequin, and it is exposed to the radiation heat flow and open flame. During the tests, the thermal parameters of the undersuit space are monitored — the temperature on the dummy surface and the passing heat flux. To measure the parameters of the thermal state of the undersuit space during the experiment at the Thermomanequin test bench, a special program was developed that allows the results (temperature and heat flow) to be displayed on a computer monitor in real time in tabular, graphical forms, as well as in the form of a color fill on the monitor on the body of the manequin. The program and the results of tests conducted at the test bench do not allow predicting burn injuries. For the possibility of conducting experiments on predicting burn injuries at the Thermomanequin test bench, according to the international standards requirements, the program for calculating burn injuries based on the values of the passing heat flow, interfaced with the programs for measuring the passing heat flow, was developed. The developed program allows using experimental data on heat fluxes from the sensors, to calculate non-stationary temperature fields; by the temperatures at the boundaries of the conjugation of the epidermis with the dermis and the dermis with the subcutaneous tissue, calculate the reduced parameter of the burn injury and determine the time to reach the values at these boundaries that characterize the occurrence of the second and third degree burns respectively.

Modeling of the thermal evolution of the cores of icy giant satellites

Questions on the composition, aggregate state, size and physical properties of the giant planets satellites cores, their thermal evolution, as well as the mechanisms of their formation, are still the subject of numerous discussions. Models of the internal structure of large icy satellites impose restrictions on the composition of satellite cores in accordance with the matter of L/LL or CI chondrites or their mixture. The temperature distributions in the cores of satellites largely determine the measure of hydration of their silicate component, the presence or absence of internal metal cores. In this paper, we present the results of numerical modeling of nonstationary temperature regimes in cores with allowance for convective transfer processes. According to the results of calculations, it can be concluded that in the presence of convection, the composition of the core largely determines the thermal evolution of the core. For example, the temperature difference between silicate and hydrosilicate composition, can reach ≈ 600 K.

DEVELOPMENT OF THE DESIGN OF A PYROLYSIS INSTALLATION FOR WASTE DISPOSAL WITH DIRECTED DISTRIBUTION OF HEAT FLOWS

Waste recycling is now gaining in importance around the world. The range of drugs used, the volume and degree of danger of waste generated by the activities of industrial institutions is increasing. As a result, the risk of epidemics increases. Therefore, the creation of an effective design of the furnace as the main unit of the pyrolysis unit is an urgent task. The purpose of the furnace environment is to create in the working chamber the necessary and optimal physical and chemical conditions for the implementation of thermotechnological, thermotechnical and mechanical processes and protection of raw materials and obtained target products from unwanted chemical processes. The following substances are used as heat extraction reagent: air, inert and recirculating gases, water, steam, etc. If necessary, a slow decrease in temperature, cooling of materials and products is carried out together with the oven. Heat transfer processes in the waste disposal plant take place in difficult conditions and are characterized by a number of specific features. One of the main features is the high intensity of heat transfer. Another feature of thermal processes is the non-stationary temperature field in the working chamber of the furnace. Heat exchange in the working chamber of the furnace is carried out in three types - thermal conductivity, convection and thermal radiation, any combination of them or all types simultaneously, but one type of heat transfer always prevails over others in full or in a certain area of the furnace.

Development of a Mathematical Model for a Workpiece Heating and Cooling in a Protective Medium while Treatment under Pressure

The paper reviews and develops the mathematical model of plastic flow during the hot-forming processes. A flat non-stationary temperature problem for a cross-section of a long solid (rolled product) of arbitrary shape with different heat transfer conditions along the perimeter of the cross-section was considered. Equations for calculation of the thermal conductivity coefficient and heat capacity of tungsten billets were obtained in the temperature range of 700 - 1500°C, based on the literature data. Analytical dependences in form of regression equations were obtained, allowing for computer calculations of physical specifications of 11x11 mm VA grade tungsten billets in form of temperature functions with accuracy sufficient for practical calculations.

A methodology for computing the relative icing degrees of logs stored in an open warehouse at ambient air temperature in winter

ABSTRACT This paper describes a methodology for mathematical modeling, computing, and research of two mutually connected problems: 2D non-stationary temperature distribution in logs stored for a long time in an open warehouse at periodically changing ambient air temperature in winter and change in the icing degrees of the logs during this time. Mathematical descriptions of the periodically changing ambient air temperature and of three types of relative icing degree of the logs that result under the influence of that temperature have been presented. These descriptions are introduced in coupled 2D non-linear mathematical models of the heat distribution in logs during their freezing and defrosting. The paper presents solutions of the models with explicit form of the finite-difference method. Results from a simulative investigation of the 2D non-stationary temperature distribution, average mass temperature, and three types of icing degree of beech logs with industrial dimensions (diameter of 0.4 m and length of 0.8 m), moisture content of 0.6 kg·kg−1, and initial temperature of 0°C during their 5 days and nights alternating freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial values below −5°C and different amplitudes are graphically presented and analyzed.

Selective Determination of Hydrogen Sulfide Using SnO2–Ag Sensor Working in Non-Stationary Temperature Regime

The application of a non-stationary regime of temperature modulation in metal oxide semiconductor sensor based on SnO2–Ag leads not only to a strongly increased sensor response, but also to a considerably improved sensor selectivity toward hydrogen sulfide. Selectivity with respect to other reducing gases (CO, NH3, H2) is about five orders of magnitude, enabling a correct selective determination of H2S in the presence of interfering gas components.

Nonstationary analysis of the extreme temperatures in Turkey

Record-breaking extreme temperatures have been measured in the last two decades all over Turkey, with recent studies detecting positive trends in extreme temperature time series. In this study, nonstationary extreme value analysis was performed on extreme temperature time series obtained from fifty stations scattered over the seven geographical regions of Turkey. Basic characterization of the data set was defined through outlier detection, homogeneity, trend detection, and stationarity tests. Trend-including non-stationary extreme temperature time series were analyzed with non-stationary Generalized Extreme Value distribution. Three main physical drivers were considered as the leading causes that trigger the observed trends in extreme temperatures over Turkey: time, teleconnection patterns of the Arctic Oscillations, and those of the North Atlantic Oscillations. The results showed that most of the absolute annual minimum and maximum temperature time series are inhomogeneous while the possible breakpoints date back to the1970s and 1990s, respectively. More than half of the absolute annual maximum time series (26/50 and many of the absolute annual minimum time series (21/50) showed a positive trend. No negative trend was detected in the extreme temperature time series. Based on the frequency analysis of the 21 annual maximum time series, the non-stationary estimations of 50-year return levels were detected to be higher than in the stationary model (between 0.44 °C and 3.73 °C). The return levels in 15 of the 20 minimum temperature time series increased from 0.11 °C up to 12.28 °C. Elevation increases the nonstationarity impact on absolute minimum temperatures and decreases it on absolute maximums. The findings in this study indicate that the consideration of non-stationarity in extreme temperature time series is a necessity during return level estimations over the study area.

Temperature stabilization of the angular velocity measuring device

The article examines the possibility of using an active two-circuit thermal control system to reduce the influence of temperature disturbances on the components of the angular velocity measuring device. Special attention is devoted to the problem of temperature stabilization in fiber-optic gyroscopes mounted in the measuring device. The study of the inhomogeneous nonstationary temperature field of the angular velocity measuring device with a two-circuit reversible thermal control system on Peltier thermal batteries is carried out. Thermal and mathematical models of the considered dynamical system are constructed. Specialized software for numerical simulation has been developed, which allows calculating and visualizing real-time inhomogeneous, three-dimensional, non-stationary temperature fields of the device under conditions of complex non-stationary thermal effects of internal and external sources. It is shown that the use of a two-circuit reversible thermal control system can help to significantly reduce the influence of external non-stationary temperature disturbances on the temperature stability of fiber-optic gyroscopes in various operating conditions, such as vacuum and weightlessness. The energy consumption and the increase in the weight and size characteristics of the device are estimated.

Analytical study of the non-stationary temperature field of a thermally thin plate

The report analytically investigates the unsteady temperature field of a plate experiencing intense thermal action. The problem is reduced to solving a singularly perturbed boundary value problem of the nonstationary thermal conductivity equation with nonlinear boundary conditions on movable borders. The approximate solution of which is obtained in the form of an asymptotic decomposition of the solution in the sense of Poincaré in degrees of small parameters, depending on the proximity of the point under consideration to the borders.

Assessment of constant and time-varying temperature schemes on the convective drying characteristics of hemp leaves

In the present study, selected mathematical drying models are evaluated for describing the convective drying of hemp (Cannabis sativa L.) leaves. Drying kinetics have been experimentally investigated in a laboratory scale convective dryer for a constant airflow velocity of 1 m s-1 and air-drying temperatures of 40, 50 and 60 °C. Non-stationary temperature conditions were also investigated for the same temperature range, under different advancing time-varying temperature profiles. Weibull formula was the most suitable mathematical expression for describing the drying kinetics for both stationary and non-stationary drying conditions. Drying at increased heating rates led to a lower final moisture content compared with the constant drying temperature levels, exposing the raw material for a shorter duration to the higher air-drying temperature.

РАСЧЕТ ЖЕЛЕЗОБЕТОННОЙ ПЛИТЫ ПЕРЕКРЫТИЯ ПРИ ВОЗДЕЙСТВИИ ПОВЫШЕННЫХ ТЕМПЕРАТУР ПОЖАРА

Розроблено методику чисельного дослідження напружено-деформованого стану залізобетонних конструкцій плит перекриттів з урахуванням нестаціонарних полів температур в арматурі і бетоні за стандартним температурним режимом і температурному режимі реальної пожежі. В рамках методики використовуються характеристики материлов, наведені в ДСТУ-Н Б EN 1992-1-2, а також вихідні дані, необхідні для застосування уточненого методу розрахунку. Ці дані встановлюються шляхом аналізу наявних в літературі експериментальних даних і характеристик матеріалів, наведених в Єврокодах. При оцінці вогнестійкості конструкцій уточненим методом розрахунку враховуються всі фактори, які справляють істотний вплив на напружено-деформований стан конструкції при пожежі. Визначають підвищення і поширення температури в конструкції в заданий момент часу (теплотехнічний розрахунок) і механічну поведінку конструкції (статичний розрахунок), при цьому враховується відповідний сценарій пожежі. Методика ілюструється на прикладі розрахунку на вогнестійкість залізобетонної плити перекриття. Проведено розрахунки з реалізацією пов'язаних термопрочностних завдань в програмному комплексі ANSYS. Проектування залізобетонної плити перекриття виконувалося в модулі Design Modeller програми ANSYS. Потім здійснювалися послідовно розрахунки в модулях TRANSIENT THERMAL і STATIC STRUCTURAL. Бетон і арматура моделюються об'ємними елементами. Підхід не вимагає прив'язки сітки кінцевих елементів до кроку арматури, що дозволяє застосовувати його до завдань з реальними розмірами. У прийнятій моделі бетону поверхня плинності складається з двох пересічних конічних поверхонь Друкера-Прагера. Результати розрахунків добре узгоджуються з представленими літературними експериментальними даними. Використання запропонованої методики дозволяє досить точно оцінити вогнестійкість залізобетонних конструкцій і прогнозувати їх напружено-деформований стан при пожежі.

Dependence of the temperature fields of a thin vertical wall on the intensity of the oncoming flow of a heated liquid

The processes of the development of free convection of ethanol in the regimes of heating the vertical wall of a rectangular cavity are experimentally investigated. The hydrodynamics in the cavity and the dependence of the temperature field on the opposite thin vertical wall are studied. Non-stationary temperature fields on a thin wall were measured with a thermal imager. The experiments were carried out at different densities of heat fluxes on the heater and at a discrete set of heights of the liquid layers.

Non-stationary temperature distribution in a thermally insulated concentric cylindrical channel with biomass moving under the influence of rotation of electrically heated helix

Non-stationary temperature distribution in a thermally insulated concentric cylindrical channel with biomass moving under the influence of rotation of electrically heated helix

Mathematical Simulation of Microstructural Phase Transformations in the Course of Welding Heating for the Case of Cladding of Protective Layer in the WWER-1000 Reactor Vessel

By using the developed finite-element models, we perform the numerical investigation of nonstationary temperature fields and the kinetics of microstructural phase transformations in the base material of the WWER -1000 reactor vessel (15Kh2NMFА steel) under the conditions of submerged-arc cladding of protective anticorrosion layers of austenitic materials. We perform the comparative analysis of the results of simulation of microstructural phase transformations obtained by using two methods of prediction of the decomposition of austenite in the process of cooling. The first method is based on the application of regression equations and the characteristic cooling time Δ t8/5. The second method is based on the diagrams of isothermal decomposition of austenite, the Avrami equation, and the Koistinen–Marburger equation. As a result of simulation of microstructural transformations under cladding, we obtain the bainite-martensite composition in the heat-affected zone of the base material of reactor vessel, which is confirmed by results of the dilatometric analysis and metallography.

Direct Method of Calculating Nonstationary Temperature Fields in Bodies of Basic Geometric Shapes

Direct Method of Calculating Nonstationary Temperature Fields in Bodies of Basic Geometric Shapes