Distribution Characteristics Of Temperature Field Research Articles

Influence of pore-crack environment on heat propagation of underground coalfield fire: A case study in Daquanhu, Xinjiang, China

The development of pores and cracks in coalfield fire area promote the abnormal temperature, the greenhouse effect, and the release of toxic gases. It is of great significance to study the dynamic distribution characteristics of temperature field and concentration field of typical gas products in a coalfield fire area under different pore-crack environments for revealing the spreading law of underground coalfield fire. In this paper, the combined effect of coal combustion chemical reaction, heat energy transmission, flue gas seepage and pore-crack environment were considered. Taking Daquanhu coalfield fire area as an example, an optimized multi-field coupling model, which included the chemical reaction of coal combustion, convection heat transfer in cracks, heat transfer in porous media, gas seepage and improved partial differential equation of pore-crack evolution was constructed. The coalfield fires area was divided into combustion zone, caving zone, sagging subsidence zone, crack zone. The evolution law of temperature field, CO2 concentration field in the coalfield fire area under different air leakage and geological crack conditions was analysed. The results showed that the temperature development of coalfield fire is divided into rapid heating stage and stable development stage. At the rapid heating stage, the greater the air leakage flow was, the faster the maximum temperature rise in the combustion zone. At the stable development stage, with the air leakage decreased, the thermal buoyancy increased. The greater the number of cracks was, the greater the area of the drying zone (673.15 K < T < 1073.15 K) closed to the crack zone. The influence of crack environment on heat flux in the sagging subsidence zone and crack zone was obvious. The total heat flow in the crack zone was about 25 times that in the caving zone. The relationship between the maximum temperature in the combustion zone and the CO2 concentration at the crack outlet showed an exponential model (ExpGro1 exponential model). The area spread by coalfield fire increased linearly with the rang of surface temperature abnormal. The research results provided a basis for judging the spread trend of coalfield fire and extracting coalfield fire of heat energy.

Semi-analytical solution for interfacial debonding of high-speed railway ballastless track under thermal loading using a quasi-dynamic method

Interfacial debonding of multi-layered ballastless track systems has proved to be one of the most common diseases in the high-speed railway during long-term operations. This paper focuses on the theoretical modeling of track temperature field and consequent bond-slip behavior between track layers under thermal loading. By establishing heat conduction differential equations, whose boundary conditions are combined with complicated geographical and meteorological factors, the temperature field of a multi-layered track structure is obtained via the integral transform technique. The reliability of the heat conduction model is well-validated by an on-site experiment in a high-speed railway line. Then, we originally extend an explicit integration algorithm for dynamics analysis to solve nonlinear statics problems with small deformation by proposing a quasi-dynamic method (QDM). Equilibrium equations of a track slab subjected to quasi-dynamic equivalent thermal loads and mixed-mode interfacial cohesive forces are constructed based on the Mindlin plate in-plane and flexural vibration equations. The application of the QDM to solve interface responses is verified by comparing results obtained from finite element (FE) software. Finally, numerical discussions are conducted to reveal the nonlinear distribution characteristics of temperature field, evolution process of the interface damage and failure modes under time-varying thermal loads, which provide a better understanding of the interfacial debonding phenomenon encountered in ballastless track systems.

Frost jacking characteristics of prefabricated cone cylindrical tower foundation in cold regions

The foundations of high-voltage transmission lines in permafrost areas are often affected by frost heaving of the soil, which leads to engineering accidents, such as falling towers or poles. The tower foundation type that has been analyzed thus far cannot meet the construction requirements well. Based on research on the prefabricated cone cylindrical (PCC) tower foundation model, indoor model tests were conducted to study the frost jacking characteristics of the tower foundation under different temperatures. The temperature field distribution characteristics and the pattern of the frost jacking displacement were determined, and the anti-frost jacking mechanism of the PCC tower foundations was analyzed. The research indicates that the following. (1) The PCC tower foundation, which combines the structural characteristics of a tapered column foundation and prefabricated foundation with the technical advantages of frost resistance and easy construction. (2) The freezing rate decreases exponentially with time, and the frost jacking displacement increases in an “S” shape. (3) The mechanical conditions for the displacement of the foundation was proposed based on the mechanical analysis. (4) To promote economy and safety, a foundation engineering design criterion has been proposed for burying the upper surface of the foundation below the freezing depth line, which can prevent engineering accidents.

Numerical and experimental investigation on heat transfer of multi-heat sources mounted on a fined radiator within embedded heat pipes in an electronic cabinet

In this paper, a finned heat sink for thermal management inside electrical cabinets was proposed to address the heat dissipation problem of some electronic equipment which are high heat flux and compact structure. The cooling system is mainly composed of four identical radiators, eight water-charged wickless L-shape heat pipes are embedded at the bottom of each radiator, and hollow fins are used in the condensation section of the heat pipes to enhance heat transfer. A thermal resistance network model of the heat pipe electric cabinet based on the superposition method was conceived. At the first part, experiments are conducted to measure the temperature of the heat source and the air in the air-flow passage. Transient and steady-state studies were carried out under different heating powers at the ambient temperature of 30 °C–35 °C. The maximum temperature difference between each heat source under forced convection is only 3.2 °C, which is more uniform than 10.36 °C in natural convection. The second part proposed a three-dimensional numerical model to further evaluate the heat transfer performance of the heat sink. The distribution characteristics of temperature field and flow field inside the cabinet are obtained by numerical calculation, and the variation of Ra number with height is further calculated. Taking the continuous junction temperature lower than 85 °C as the condition that the components in the cabinet can operate safely, the limit heat dissipation of the cooling device through natural convection can reach 763 W.

Numerical investigation of thermal parameter characteristics of the airfield runway adherent layer in permafrost region of Northeast China

The thermal parameters of adherent layer are of great significance to the distribution characteristics of temperature field and foundation stability control of runway in permafrost region. This paper investigated the effects of annual range of temperature ( A ), annual average temperature ( T A ), and other factors on the adherent layer thickness ( H ), temperature amplitude ( A 0 ), and annual average ground temperature ( T 0 ), and further analyzed the thermal parameters of the adherent layer by using the FEM (Finite Element Model) roadbed temperature field and experimental data. The results indicate: A and average monthly total solar radiation ( Q ) have the most serious on H . A numerical method for determining the parameters of the adherent layer based on various conditions such as A and T A was proposed by multiple regression. The temperature fields of the three types of pavements obtained by FEM and the experimental data were compared with the numerical calculation results for verification, and the conclusions were in close agreement, illustrating that the proposed method for calculating the parameters of the adherent layer is reasonable and effective. The research results extend the application region of adherent layer theory and provide a reference for runway construction in the permafrost region of Northeast China.

Finite element-based machine learning approach for optimization of process parameters to produce silicon carbide ceramic complex parts

Design and fabrication of silicon carbide ceramic complex parts introduce considerable difficulties during injection molding. Due to the great importance in processing optimization, an accurate prediction on the stress and displacement is required to obtain the desired final product. In this paper, a conceptual framework on combination of finite element method (FEM) and machine learning (ML) method was developed to optimize the injection molding process, which can be used to manufacture large-aperture silicon carbide mirror. The distribution characteristics of temperature field and stress field were extracted from FEM simulation to understand the injection molding process and construct database for ML modeling. To select the most appropriate model, the predictive performance of three ML models were estimated, including generalized regression neural network (GRNN), back propagation neural network (BPNN) and extreme learning machine (ELM). The results show that the developed ELM model exhibits exceptional predictive performance and can be utilized to predict the stress and displacement of the green body. This work allows us to obtain reasonable technique parameters with particular attention to the loading speed and provides some fundamental guidance for the fabrication of lightweight SiC ceramic optical mirror.

Simulation research on ONAN transformer winding temperature field based on temperature rise test

Studying the oil-natural-air-natural (ONAN) transformer?s temperature field distribution characteristics and hot spot temperature rise during operation is a key step to evaluate the thermal insulation life of this type of transformer. Firstly, considering the transverse oil passages between the windings and the guiding effect of the oil baffle on the oil flow, this paper takes 35 kV ONAN transformer windings as the research object, which establishes the corresponding electromagnetic-thermal-fluid coupling model and uses the finite element method to calculate the overall distribution of the internal winding temperature field. The calculation results show that when the ONAN transformer reaches thermal equilibrium, the axial temperature distribution of the windings is extremely uneven due to the influence of the transformer oil flow rate, whose difference between both ends is as high as 17.4?. However, the existence of the oil baffle increases the flow velocity of the inter-turn transverse oil passage to 12 times of the original. Affected by this, the oil temperature difference between the two ends of the oil baffle is as high as 2.42?. Secondly, this paper conducted a short-circuit temperature rise test on the test prototype, and selected the different axial heights (18%, 72%, 96%, etc.) of the windings on both sides of the transformer as the characteristic sample points for embedding temperature measurement fiber for real-time temperature monitoring. After comparison, it is found that the simulation calculation is basically consistent with experiment data, and the relative error of the two is less than 3.3%.

Experimental research on characteristics of temperature field distribution of mild moxibustion and sparrow-pecking moxibustion

To explore the temperature field distribution and variation rules during treatment with mild moxibustion and sparrow-pecking moxibustion of TCM. Six healthy subjects were selected. Mild moxibustion and sparrow-pecking moxibustion were exerted at Zusanli (ST 36) respectively, for 25 min. Using infrared thermal imaging instrument, the temperature field distribution was measured during moxibustion at Zusanli (ST 36). The simulated thermometer was adopted to measure the temperature field distribution during moxibustion at the imitated cortex. At 20 min of mild moxibustion and sparrow-pecking moxibustion, the temperature field distribution generated by moxibustion was observed at the imitated cortex and Zusanli (ST 36) separately. The temperature values were collected at the sites 0.7, 2.1 and 3.5 cm far from the center of the moxibustion-exerted places successively, and then the characteristics of temperature field distribution and variation rules were compared between different moxibustion methods at the imitated cortex and Zusanli (ST 36). At 20 min of mild moxibustion and sparrow-pecking moxibustion at Zusanli (ST 36), the temperature field distribution focused on the center of moxibustion-exerted site and the temperature was reduced to all directions and illustrated as a curved surface graph, whereas, the temperature field distribution at the imitated cortex was consistent with that at Zusanli (ST 36). With mild moxibustion, the temperature field was distributed uniformly along the longitudinal temperature gradient; whereas, with sparrow-pecking moxibustion, the longitudinal temperature of the temperature field was greatly different, in which, the maximum temperature and the average temperature were higher than those with mild moxibustion respectively and the first time up to the peak value of sparrow-pecking moxibustion was shorter than that with mild moxibustion. The thermal transfer was presented at the non-moxibustion exerted areas during the moxibustion experiment at Zusanli (ST 36). A distance feature is presented in the temperature field measured by simulated thermometer and generated under suspension moxibustion at Zusanli (ST 36). The warm stimulation effect of sparrow-pecking moxibustion is much more obvious at the moxibustion-exerted center as compared with mild moxibustion and the area of warm stimulation generated by sparrow-pecking moxibustion is more concentrated as compared with mild moxibustion. The radiation energy produced by suspension moxibustion is scattered and attenuated in skin tissue, resulting in a certain temperature gradient in the temperature field. The warm stimulation generated at skin surface by moxibustion has a warming-dredging effect.

The Combustion Numerical Simulation of a Liquid Slag Pulverized Coal Burner in the High Temperature Secondary Air

Taking a liquid slag pulverized coal burner as the research object, the combustion characteristics of the burner in different high temperature secondary air were simulated by Fluent commercial software, and the combustion characteristics of temperature field distribution and the change of component concentration were obtained. The simulation results show that the burner can form a front ignition zone, the air vortex low temperature zone, the central DC flame and the annular flame in the hot state. It can be found that increasing the secondary air temperature can improve the combustion intensity of the burner, promote the formation of CO, and form a high temperature reduction zone, which is conducive to inhibiting pollutant emissions. The research results provide theoretical support for the application of the burner in practice.

STUDY ON TEMPERATURE CHARACTERISTICS OF HIGH LOAD PRESS

Based on the finite element analysis software ABAQUS, the steady and transient temperature field of the high load press is analyzed, and the temperature field distribution characteristics of the ejector cylinder, the moving beam steel wire layer and the frame steel wire layer are obtained. The results show that the heat source can be effectively blocked by adding thermal insulation pad between the mold and the upper mold seat, which is better than the scheme of adding thermal insulation pad at both ends of the ejector cylinder, and the temperature control effect is obvious. The improvement of the surface heat transfer coefficient and the local surface heat transfer coefficient is not obvious for the improvement of the oil temperature.

Study on Loss and Temperature Increases in Hollow Oil-immersed Reactors

Oil-immersed hollow reactors have been applied to high-voltage frequency-modulated resonant power supplies due to their favorable linearity and high insulation strength. A high-quality reactor is the key component of a high-voltage test system. The characteristics of loss and temperature-rise characteristics are the core factors affecting the quality factor of the reactor. In this paper, a finite-element numerical simulation model was established based on a large capacity series resonance test system for a 500-kV submarine cable in China. The eddy current loss, AC resistance loss, and circulating current loss of the oil-immersed air-core reactor were calculated. With these as a foundation, the flow and temperature field distribution characteristics were obtained for an oil-immersed hollow reactor through the coupling of magnetic heat and flow field. Finally, the temperature distribution characteristics of the reactor were compared with the dates obtained from the release testing, and the reliability of the calculation model was verified.

Thermal modelling for conformal polishing in inductively coupled atmospheric pressure plasma processing

Inductively coupled atmospheric pressure plasma processing (IC-APPP) is a novel polishing technique for silica-based optics to quickly mitigate the surface or subsurface damage due to its high efficiency and low cost. However, theoretically uniform removal of materials is difficult to achieve because of complex thermal effect. In this paper, numerical modelling and experimental study of global temperature field in IC-APPP is presented. First, a transient heat transfer model is established using finite element analysis to study the characteristics of temperature field distribution during the process. Then, the effects of substrate geometry and processing parameters are systematically analyzed. Finally, conformal polishing experiments are carried out to illustrate the correlation between the effectiveness of uniform removal and the temperature field. The surface shape can be maintained well with optimal processing parameters in IC-APPP.

Performance enhancement of microwave assisted regeneration in a wall-flow diesel particulate filter based on field synergy theory

In this work, a three-dimensional mathematical model is established to investigate the flow and the heat transfer of the combustion process and the distribution characteristics of temperature field in the wall-flow in porous media of the wall-flow diesel particulate filter (DPF) based on the Field Synergy Theory (FST). The results indicate that there is the smallest temperature uniformity coefficient in wall-flow DPF when the inlet velocity is 36 m/s. And at first, the microwave assisted regeneration temperature increases and then decreases as the exhaust temperature rises which is affected by the exhaust temperature. The data indicate that the inlet pressure can change the angle between velocity vector and temperature gradient, which leads to the change of synergy degree of the velocity field and temperature field. When the inlet pressure is 0.08 MPa, there is an optimal synergy degree with the maximum average temperature.

Measurement and Simulation of Temperature Field of Concrete Box Girder in Northwest Severely Cold Area

This study evaluated the characteristics of temperature field distribution of the concrete box girder based on the middle bridge of Xiaosha River, and the effects of temperature in severely cold area were determined through experiments and finite element model (FEM) analysis. An FEM model of the concrete box girder considering the temperature field was established based on heat transfer theory to verify the accuracy of the model. Moreover, the calculation of the vertical temperature distribution and the temperature distribution along the web plate was conducted. The distribution along the through-thickness direction of the bottom plate and the temperature drop caused by cold waves was evaluated. Results suggest that the published codes and guidebooks were relevant. The effect of the most unfavorable condition of temperature load was also calculated. The result drawn from this research shows that the distribution of temperature field at the cross sections in the severely cold area differed greatly from that in the current code. However, the temperature difference in the top flange was not evident, whereas it was much larger in the bottom flange. The temperature in the web was higher than that in the top flange under solar radiation and was lower during cooling. The results of the temperature effect were much more critical than the result calculated using the vertical temperature gradient in the current code. The tensile stress produced by temperature load may cause cracks. Consequently, sufficient attention should be paid to the damage of thermal effects when calculating the concrete box girder in the northwest of the severely cold area.

Comparison of temperature field distribution between cement preclinkering technology and cement precalcining technology

Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology, we studied the characteristics of temperature field distribution of cement preclinkering technology systems including cyclone preheater, preclinkering furnace, and rotary kiln. We used numerical simulation method to obtain data of temperature field distribution.Some results are found by system study. The ratio of tail coal of cement preclinkering technology is about 70%, and raw meal temperature can reach 1070 °C. Shorter L/D kiln type of preclinkering technology can obtain more stable calcining zone temperature. The highest solid temperature of cement preclinkering technology is higher than 80 °C, and high temperature region (>1450 °C) length is 2 times, which is beneficial for calcining clinker and higher clinker quality. So cement preclinkering technology can obtain more performance temperature filed, which improves both the solid-phase reaction and liquid-phase reaction.

Analysis of the Fire-Resistance of Beam String Structure

The mechanical properties, such as yield strength, modulus of elasticity of steel cable and its mechanics model were obtained based on the mechanical properties of steel cable under the high temperature test results. Nonlinear finite element numerical analysis method was established based on the time integral effect considering. The characteristics of temperature field distribution, displacement and stress are discussed. The reuslts show that: BSS has better spatial work performance, the weak area of the structure is near the far side, the main reason of large deformation is the reduce of stiffness and strength.

Analysis of the Fire-Resistance of Suspen Dome Structure

Based on the mechanical properties of steel cable under the high temperature test results, the mechanical properties, such as yield strength, modulus of elasticity of steel cable and its mechanics model were obtained. Nonlinear numerical analysis method was established based on the time integral effect. Through the analysis of the suspen-dome structure, this paper discusses the characteristics of temperature field distribution, displacement and stress. The results show that: suspen-dome structure has better spatial work performance; the weak area of the structure is at the central, the main reason of large deformation is the reduction of stiffness and strength.

Characteristics of Geo‐Temperature Gradient Distribution in the Kuqa Foreland Basin on the North Edge of the Tarim Basin, Western China

AbstractBased on the geo‐temperature data of 109 wells in the Kuqa foreland basin on the north edge of the Tarim basin, the characteristics of temperature field distribution are presented. The average geo‐temperature gradients of different structural units of Kuqa basin range from 18°C/km to 28°C/km, which are comparably lower than those of any other large and middle size basins in China. So the Kuqa foreland basin is globally a cold one with lower temperature. In detail, the distribution of geo‐temperature gradient of Kuqa foreland basin can be described as following. The mountain frontier belts including the Yiqikelike, Kelasu and Dawanqi areas have relatively high geo‐temperature gradients compared with other structural units of Kuqa. From the north to south of Kuqa, the geo‐temperature gradient decreases gradually. At the south of Kuqa, the geo‐temperature gradient is evidently different. In general, the geo‐temperature gradients decrease with the increasing of depth, tending to be identical at depth. But the rates of decrease are all different at different tectonic settings. The relationship between geo‐temperature gradient and formation and tectonic evolution of basin in relation to hydrocarbon exploration is also discussed.