Temperature Distribution Law Research Articles

The Flow-Heat Coupling Study of Cooling Circulating Channel of Magnetic Drive Pump

The medium in the cooling circulation channel of the magnetic drive centrifugal pump will take away the heat generated by the magnetic eddy current and bearing friction in time to avoid the high temperature demagnetization phenomenon of the permanent magnets. Therefore, the reasonable design of the cooling circulation channel directly affects the stable operation of the magnetic drive centrifugal pump. In this paper, the heat exchange and temperature distribution in the cooling circulating channel of magnetic drive pump are studied by means of numerical calculation of fluid-heat coupling and external characteristic test. The temperature distribution and development law of the isolation sleeve clearance, the bottom of the isolation sleeve and the reflow hole are analysed emphatically, and the convection heat transfer coefficient distribution in the isolation sleeve clearance is studied.

Research of Safe Technology of Impregnation of Heated Reinforcing Materials with Binder

Prepreg manufacturing process is one of the most important preparatory technological processes, quality of which has the decisive influence on the physical, mechanical, processing and operational characteristics of the finished composite product. However, manufacturing of prepregs is associated with a number of harmful factors, negatively affecting the participants in the technological process and the environment. Consequently, significant additional costs are required in order to ensure specified maximum permissible levels and concentrations of the harmful products released by the components of polymeric composite materials in the product manufacturing process. The paper deals with the study of peculiarities and efficiency of impregnation of the heated reinforcing material using solvent-free binder. The method for predicting the optimal process parameters of binder solutions for impregnation of prepregs, taking into account the safety of production activity, has been developed. The problem of thermal conductivity from the heated reinforcing material to the binder, which allowed establishing the law of temperature distribution over the depth of the impregnating bath, depending on the duration of continuous impregnation, has been solved. It is found that the binder, with the duration of impregnation even within one working shift, heats up to the temperatures excluding the formation of centers of exothermic polymerization reaction in it. It indicates the availability of the effective regimes of impregnation using the method under study. The paper proposes the practical ways of improvement of the investigated method of impregnation by varying the wavelength, programmed change of the temperature of the reinforcing material at the entry to the bath, and setting of the optimal coordinates of the binder supply as it is drawn in the process of continuous impregnation of the reinforcing material.

Numerical analysis of heat transfer between air inside and outside the tunnel caused by piston action

Piston action can affect the thermal environment inside the tunnel by changing the air pressure and velocity. This is extremely unfavorable for tunnels in cold regions because it causes frost damage in cold season. Understanding the influence of piston action on the air temperature distribution inside the tunnel can help us determine the length and location of frost damage. In this paper, a heat transfer numerical model considering piston action is developed. And then, a high-speed railway tunnel in the northeast of China is taken as an example to explore the temperature distribution laws via computational fluid dynamic (CFD). Afterwards, the effects of air temperature outside the tunnel and train velocity on temperature distribution are analyzed. The results show that the piston action can accelerate the heat transfer between cold air outside and inside the tunnel, the anti-freezing length near tunnel entrance and exit must be extended based on the calculation result of existed empirical formula. Before the train enters the tunnel, the freezing length near tunnel entrance is 1158 m. After the train passing through the tunnel, the freezing length near tunnel entrance is between 1495 m and 1497 m when the air temperature outside the tunnel decreases from −1 °C to −15 °C. Under different train velocities (80 km/h, 130 km/h, 160 km/h, 200 km/h and 250 km/h), the freezing lengths near tunnel entrance are 1458 m, 1469 m, 1472 m, 1497 m, 1498 m and its near tunnel exit are 330 m, 342 m, 349 m, 356 m, 357 m, respectively. In the section of 50 m away from tunnel entrance, the air temperature near the train changes suddenly, while the air temperature far away from the train changes gently. After the train passing through the tunnel, the air temperature inside the tunnel is consistent to that outside the tunnel within a specific distance from entrance. This study provides a guideline and references for the structure design and the construction of anti-freezing measurements for the tunnels in cold regions.

Modelling of the temperature distribution based on equivalent heat transfer theory and anisotropic characteristics of honeycomb core during milling of aluminum honeycomb core

The honeycomb sandwich structure has been widely used in the field of aerospace owing to extremely high specific strength and specific rigidity. However, the honeycomb core has anisotropic mechanical characteristics and in-plane weak rigidity, which brings new challenges to the cutting process. In this paper, a three-way equivalent heat conduction model including heat conduction and heat convection in the cutting process was established based on the structural characteristics of the honeycomb core. As for the milling cutter combined with the crushing blade and circular blade specified for aluminum honeycomb core, the moving surface heat source of the crushing blade and the moving line heat source of the circular blade during the milling process were proposed. A prediction model of temperature distribution in the milling of aluminum honeycomb core based on the two heat moving sources was established and verified by the milling experiments. Finally, the temperature distribution law and heat affected area of the honeycomb core during the milling process were studied. It was found that the milling temperature of the honeycomb core maintained a high temperature in the contact area, but fell sharply outside the contact area. Moreover, the heat affected area of the milling heat does not exceed three honeycomb cores.

Experiment study and refined modeling of temperature field of steel-concrete composite beam bridges

The temperature field and its effect are important issues related to the design and construction of bridges. For steel–concrete composite bridges, the huge difference in thermal performance between steel and concrete makes the temperature field distribution and variation more complicated. In this paper, an indoor baking lamp radiation experiment with controllable parameters is carried out on a group of two steel–concrete composite beam specimens for the study of temperature field. The temperature time-history and distribution laws of the specimen during heating and cooling process are observed and analyzed. Furthermore, a refined numerical model of the solar temperature field of the composite bridge is established and verified by the baking lamp radiation experiment. The proposed refined numerical model of the temperature field of the steel–concrete composite bridge realizes the temperature field analysis of various cross-sections of composite bridges and can automatically consider the shielding effect of the flange on the web, providing a useful tool for the modeling of and analysis of the temperature field of composite bridges.

Failure analysis on rubber sealing structure of mandrel hanger and improvement in extreme environments

In view of the failure of the sealing structure of mandrel hanger under high pressure and extreme temperature environment, according to the sealing structure characteristics and application requirements of conventional mandrel hanger, based on the principle of the minimum sealing pressure ratio of metal sealing surface and the constitutive model of rubber material, the advantages and disadvantages of three conventional sealing structures are analyzed and compared. Based on the heat conduction theory and the energy conservation equation of thermal coupling, the transient temperature field model of the hanger seal structure is established. The heat transfer analysis and thermo-mechanical coupling calculation of the new metal seal structure are carried out at extreme temperature. The results show that the contact pressure on the double U and single U sealing rings is greater than 140 MPa at extreme temperature, which meets the principle of minimum sealing pressure ratio. The temperature distribution law of the conventional rubber structure under the temperature and pressure load is analyzed, and the reason of early failure of rubber is found. The mandrel hanger of full metal sealing structure is used in the field. The mandrel hanger of full metal have been tested for more than 20 times of gas pressure. The pressure is stable and the sealing effect is good. The test results show that this new structure has the advantages of good seal performance.

A virtual sensor simulation system of a flower greenhouse coupled with a new temperature microclimate model using three-dimensional CFD

Greenhouse culture, as a high-yield and efficient production technology, has become an important means to increase crop yield and quality. Greenhouse environmental monitoring is a key practice affecting the yield and quality of greenhouse crops. Meeting the growth needs of crops while reducing the cost of environmental monitoring has become an urgent and difficult scientific problem. Sensor technology with the addition of computational fluid dynamics (CFD) technique is a new method for addressing this issue. However, this CFD approach generally cannot monitor the greenhouse environment in real time. This study aims to establish a virtual sensor system based on the external environment of a climate model to form a closed-loop network using a finite volume CFD code (ANSYS FLUENT 19.0). An experiment is conducted on a flower greenhouse, and a 3D transient CFD is implemented including a meshing and turbulence model in the MATLAB interface program. Furthermore, a temperature model based on the external greenhouse environment is established using a regression method from the model, and a virtual sensor model of greenhouse temperature is established using a feedback method. The results show that the simulation satisfied the temperature distribution law, revealing that virtual sensors and physical sensors can work together to monitor the greenhouse environment.

Temperature Field and Gradient Effect of a Steel‐Concrete Composite Box Girder Bridge

To study the effect of the temperature field and gradient of a steel‐concrete composite box girder bridge, a 5 × 35 continuous composite box girder bridge is used as the research object. The temperature measuring point is set by selecting a typical cross section, and the temperature change data are measured. The temperature field of the different positions in the composite box girder bridge is studied, the global and local temperature differences are compared, and the law of temperature distribution and the main factors affecting the temperature field are formulated. The most unfavourable expression function of the vertical temperature gradient of the section is simulated using the measured data, the existing standard temperature gradient mode is compared, the finite element model of the bridge is established, and the influence of the actual temperature gradient mode on the stress and deformation of the composite girder is further analysed. The conclusions show that the temperature differences of different azimuth sections and the local temperature differences between the steel and concrete joint parts of the steel‐concrete composite box girder bridge are not significant. The temperature gradient heating and cooling model fitted by the measured temperature field can be used as a reference for the structural design of similar local bridges.

Numerical Analysis of Ultimate Mechanical Characteristics of Suspension Bridges’s Cable in High Temperature Fire

Relying on the joint research project, research is carried out on the ultimate mechanical characteristics of suspension bridge slings under high temperature fire. The establishment of a local transient temperature field heat transfer model based on the FDS software, and the analysis of the temperature distribution law of the fire source at different wind speeds. The most unfavorable fire condition is the combination of the fire source heat release rate of 300MW and the wind speed of 14m/s; the overall structure model of the bridge is modeled by ANSYS software. Firstly, the modal analysis of the whole bridge model is carried out to verify the accuracy of the modeling, and then the thermal structural coupling analysis is carried out under the most unfavorable fire conditions to obtain the structural response of the whole bridge structure under the sling fire. According to the change trend of the structure response of the cable under fire, the fire resistance limit of the bridge structure is obtained as 460°C; Under the most unfavorable fire burning situation, when the limit number of broken cable in the span is 3, the cable will be caused into collapsing continuously; the composite protective layer has a significant effect on the fire resistance of the cable.

A Positioning Method of Temperature Sensors for Monitoring Dam Global Thermal Field

During the concrete pouring process of a dam construction, timely and accurate temperature monitoring is of great significance to reveal the thermal distribution characteristics and evolution process, and control concrete cracking. In this study, a positioning method of temperature sensors (PMTS) in a concrete dam is developed to determine the arrangement of temperature sensors quantitatively. The proposed positioning method is related to the restructured thermal field based on the natural neighbor interpolation algorithm, and the cross-validation. Based on the method, thermometers, distributed optical fibers and infrared thermal imagers are optimally installed in a super-high arch dam for real-time measurement of concrete temperature. The results show that the PMTS is reasonable and reliable for obtaining the dam global thermal field. The on-site temperature monitoring data indicate that the time and space temperature distribution law of the restructured thermal field is consistent with the actual situation of the super-high arch dam. In addition, the cons and pros, and improvement of the PMTS are further discussed. The proposed PMTS is a valuable method to monitor the global thermal field of concrete dams.

Simulation Study on the Temperature Field of Iron-based Powder Metallurgy Friction Pair

For the iron-based powder metallurgical friction pair under high-speed braking conditions, the structural model and physical model of the friction pair were established, and the finite element software ABAQUS was used to calculate and analyze the temperature field and distribution law of the friction pair during friction braking. The results show that during friction braking, the temperature at the outer diameter of the contact surface of the friction pair is the highest, and the temperature at the inner diameter of the edge of the chip removal tank is the lowest. During braking, the temperature of friction pair increases first and then decreases with time.

The temperature rise characteristics analysis and experiment of GMA

The giant magnetostrictive actuator (GMA) with giant magnetostrictive material (GMM) as the core component has wide applications in the field of precision drive and control. In this paper, through the analysis of the GMA coil, the loss and temperature rise characteristics of the GMA have been studied. Then, COMSOL Multiphysics software has been used to model the heat source distribution of the GMM actuator, and the factors affecting the working temperature of the GMM rod have been analyzed. Finally, based on the use requirements of the GMA, magnetic field, and internal temperature distribution characteristics, the heat dissipation scheme of the coil is proposed, and the experimental platform of the GMA with a thermal compensation function is built to verify the temperature characteristics and thermal compensation effect. Studying the internal temperature distribution law of the GMA not only has a guiding significance for the temperature control of the actuator and the design of the cooling system but also reduces the influence of the coil thermal effect on the performance of the transducer and lays the foundation for making full use of the GMM’s potential in high-power transducers.

Isoniazid thermal runaway simulation based on ARC data

The law of fire occurring in the reaction of self-reactive substances is unique, when heated, comparing with common solid combustibles. In this paper, the possible thermal runaway reaction of Isoniazid storage was studied. Combined with the analysis of Isoniazid thermal stability characteristics, Fire Dynamics Simulator (FDS) was used to simulate the Isoniazid storage fire. The temperature distribution of Isoniazid storage was obtained. According to the simulation results, the temperature field of Isoniazid storage was analyzed by regression. The law of temperature distribution with height, time and distance from the center of ceiling was obtained. It was found that the ceiling temperature was highest at different heights. On the ceiling, the temperature was highest in the center. From the center to the sides, the temperature tended to drop. Therefore, when setting up the self-spraying fire extinguishing system, the sprinkler head protection roof needs to be set up, and for the stack center position, the sprinkler head should be protected.

Research on the metamorphic layer of silicon nitride ceramic under high temperature based on molecular dynamics

The high temperature of the grinding area at the engineering ceramic materials processing is one of the main factors affecting the quality of processing and the performance of parts. In order to reveal the law of temperature distribution of silicon, nitride ceramic grinding and its mechanism of action on surface quality. The process of machining silicon nitride ceramic material is simulated based on the established molecular dynamics model of the nanometric grinding of silicon nitride. The influence of grinding parameters on the nanometric grinding process is studied from the variation law of grinding temperature and the evolution of system energy, as well as the formation of grinding surface and metamorphic layer during machining. And the results of the experiment were compared with the theoretical research. With the increasing of grinding depth and speed of diamond grains, the energy released during the deformation and amorphous phase change of the atomic lattice get increased, and the grinding temperature get increased. The high grinding temperature will cause amorphous phase change in silicon nitride ceramics, and the amorphous atoms are recombined with the atomic bonds of the processed surface to form a metamorphic layer of the processed surface. The effect of grinding parameters on temperature changes from large to small is grinding wheel line speed, workpiece feeding speed, and grinding depth. There is an important effect on improving the surface machining quality and the service life of parts of engineering ceramics such as silicon nitride from the results of this paper, and it also plays an important role in reducing the effect of grinding temperature on the surface quality.

Numerical modeling of thermomechanical processes in heat-resistant alloys

This article presents a numerical simulation of thermomechanical processes in heat-resistant alloys. The authors develop the law of temperature distribution along the length of the physical body, which is considered as a rod of alloy EI-617. The authors also investigated the dependence of the magnitude of the elongation of the rod from a given temperature. To do this, the rod is conditionally divided into several elements, and then the study is carried out in one area. To determine the temperature dependence, the temperature distribution field is approximated by a full polynomial of the second degree, and approximation spline functions are introduced. Using a temperature gradient for one element, the functional expression characterizing the total thermal energy is written, first for the (n-1) element, then for the last n-th element. The total thermal energy is expressed by the formula . By minimizing the total thermal energy, we obtain a system of algebraic equations for determining the nodal values of temperatures. Applying the obtained values, the elongation of the element due to thermal expansion is calculated. The relationship between the temperature T, elongation DlT , «tensile» force R , and «tensile stress» . is shown in the work. It is shown that with increasing temperature, the above values proportionally increase.

Experimental Investigation on Temperature Profiles at Ceiling and Door of Subway Carriage Fire

Previous studies usually used the common tunnel model and paid little attention to the propagation characteristics of fire in the carriage structure with multiple lateral openings. In the current study, experiments were carried out in a reduced-scale (1:5) subway carriage model to study the propagation characteristics of carriage fire. The main focuses were on the temperature contour profiles and distribution laws under the ceiling and at different doors inside the carriage. Results show that although the status of the side door of the carriage does not have a significant effect on the mass loss rate of fuel combustion, the temperature distribution under the ceiling will be affected under the effect of the smoke overflow of the door opening. The effect of door status on the longitudinal ceiling temperature is mainly on the area between the fire source and the adjacent door. For the transverse ceiling temperature above the fire source, the effect of the status of the door is significant with the increase of the fire source. Besides, the temperature contour profile at the door shows regular distribution. In the process of gradually increasing the temperature as the height increases, the isotherm gradually changes from a horizontal straight line to two inverted triangular sides, the temperature at the door has been basically in the ambient temperature from the dimensionless height (normalized by the height of the door) below 0.6. The measured radiation at the upper part of the carriage end is about 5 times higher than that in the middle of the door adjacent to the fire source, and the ratio is not significantly affected by the heat release rate. The results of this study can be of use to the fire-protection community to better understand fire dynamics.

Study on the Thermal Performance and Temperature Distribution of Ball Bearings in the Traction Motor of a High-Speed EMU

The transient thermal performance of rolling bearings affects the mechanical performance and system safety of traction motors. Most of the traditional empirical formulas used in temperature analysis have been simplified and cannot be completely applied to the calculation of heat generation and convection heat transfer coefficients. Based on the comparative analysis of finite element transient temperature and experimental data, this paper proposes a correction method of mathematical model and derives an accurate calculation formula for the heat generation and lubricant convection heat transfer coefficient of ball bearings applicable for the non-driving end in the traction motor of a high-speed EMU (Electric Multiple Unit). The accuracy of the results has been verified by durability experiment data. In addition, with changes in speed, radial load and other factors taken into account, we have analyzed the influence of these time-varying factors on ball bearing temperature, as well as the temperature distribution law of each component in a grease-lubricated bearing, in a bid to lay a foundation for follow-up research on the heat transfer laws of traction motors and rolling bearings.

Mathematical Models for Determining the Distribution of Fluid Flow Temperature along the Wellbore and Horizontal Pipeline

This paper presents a proposed new indirect method determining instantly oil well debit using developed mathematical models. As a result integrated analysis using the models it has been revealed correlation between oil well debit and well throw out flow temperature. Therefore putting purpose was obtained. Mathematical models are developed for the distribution of fluid flow temperature along the length of the tubing from the well bottom to the wellhead and along the length of the oil pipeline from the collector of oil wells to the oil treatment unit. On the basis of experimental data, the authors propose formulas in the form of the relationship between oil emulsion (OE) viscosity, the flow temperature and concentration of water globule in OE and the coefficient of heat transfer from the fluid flow in the wellbore (WB) to the rock, and heat capacity and thermal conductivity of gas, water, rock and steel of the WB walls. This effect is demonstrated in the constructed diagrams. It is shown bottom temperature jump as a result of the Joule Thomson drosseling effect then connective transmitted up at flow rate v. In such case well-head or well outlet oil mixture (OM) flow temperature depend more of volume of stream flow than of bottom hole temperature. Thought in the paper, do not taking into consideration great casing annulus areas influence to the well outlet flow temperature. As shown from supporting paper the relative values og the thermal conductivity of the liquid column and gas column present in the casing annulus order less than well bore (WB) wall thermal conductivity. Consequently well outlet OM flow temperature will depends not only of the volume of stream flow, also of the bottom hole temperature and of the gas column and liquid column.A new method for determining the oil well flow rate by measuring the downstream temperature is developed. A mathematical model is proposed that allows calculating the thermal profile of the fluid along the wellbore for determining the oil well flow rate with account of the geothermal gradient in the rock surrounding the wellbore. It is shown, that unlike the existing methods the new proposed method allows determining the instantaneous discharge of a well very easily. One of the actual challenges in fluid (oil, water and gas) transportation from wells to oil treatment installation is determination of a law of temperature distribution along the length of a pipeline at low ambient temperature. That temperature leads to increase in viscosity and deposition of wax on inner surface of a pipe. To overcome that challenge it is needed to consider several defining characteristics of formation fluid (FF) flow. Complexity of a solution is caused by two factors. From the one hand, in most cases (especially on a late stage of field development) FF is an oil emulsion (OE) that contains gas bubbles. From the other hand, temperature gradient between fluid flow and the environment has significant value (especially in the winter period of the year). At the same time, the higher content of emulsified water droplets (EWD) in OE and lower flow temperature, the higher FF viscosity, and consequently productivity (efficiency) of oil pumping system is reduced. Performed research and analysis of field experimental data showed that a function of oil viscosity versus temperature has a hyperbolic law; a function of OE viscosity versus concentration of EWD has a parabolic one. A heat balance for a certain section of a pipeline in steady state of fluid motion using a method of separation of variables was established taking into account above mentioned factors, Fourier’s empirical laws on heat conductivity and Newton’s law on heat transfer. As a result, unlike existing works, an exponential law of distribution of temperature along the length of a pipeline is obtained. A law takes into account nonlinear nature of change in viscosity of OE from change in temperature of flow and concentration of water in an emulsion. As a result, in contrast to the existing works, the proposed exponential law of temperature distribution along the length of the pipeline is obtained, taking into account the nonlinear nature of variation of OE viscosity with the change in the flow temperature and the concentration of water in the emulsion. The results of the calculation are presented in the form of a table and graphs.

Numerical simulation and experimental investigation on three-dimensional modelling of single-track geometry and temperature evolution by laser cladding

Investigation of the temperature distribution law in molten pool during the laser cladding process and the varying principle of the forming parts’ cross section sizes to obtain optimum process parameters is essential to improve the precision of deposited parts. In this paper, a three-dimensional numerical single-track processing prediction model (STPPM) in laser cladding was established. The Gaussian distribution heat source was applied. Based on the element birth and death method, the transient temperature field and the geometry of the cladding could be calculated simultaneously by considering the temperature rise of the powder particles, laser energy attenuation and the material phase transition. With the prediction error less than 6.6% for track width and track height, approximately 3.1% for the maximum temperature, numerical simulation results of the track profile agreed well with the experiment results for 316 stainless steel material, indicating the validity of the STPPM. The effects of laser power and scanning speed on the geometry and temperature distribution of cladding were analyzed on the basis of the STPPM and experimentally proved. The results show that track height, width and the temperature in molten pool decreased accordingly with the increase of scanning speed. In addition, track width and the temperature in molten pool increased with the laser power while the track height stabilized. Research in this paper would contribute to minimizing the number of tentative experiments in laser cladding process and the experimental costs, meanwhile improving deposition efficiency during the processing.

Study on the Effect of the Obstacle on Heat Transfer Oxidation Spontaneous Combustion Characteristic of Coal Gangue Fracture

ABSTRACT To address the coal gangue fracture heat transfer problem, the law of heat transfers and temperature distribution in the coal gangue fracture is studied. The temperature distribution in a coal gangue fracture under 12 conditions (with or without the obstacle, and various heat flows) is simulated via Fluent numerical simulation. The results show that the heat flow velocity, temperature and obstacle are important factors in inhibiting heat transfer oxidation spontaneous combustion in the coal gangue fracture. When the heat flow temperature is constant, the low-velocity heat flow causes a large temperature drops in the coal gangue fracture; when the heat flow velocity is constant, the high-temperature heat flow also produces a large temperature drops effect; when the obstacle is present and the heat flow produces vortex pass through the obstacle, increasing the energy loss in the coal gangue fracture, causing the temperature in the coal gangue fracture to drop rapidly, and reach the lowest in the position of the obstacle. Obstacles can effectively inhibit the heat transfer characteristics in the coal gangue fracture and reduce the risks of oxidation spontaneous combustion of gangue after grouting.