Influence Of Temperature Distribution Research Articles

Temperature distribution in multichip IGBT module and its impact on collector current sharing

Multichip Insulated Gate Bipolar Transistor (IGBT) power modules are widely used in high power applications. However, the parallel connection of IGBT chips results in an inhomogeneous temperature/current distribution. In this paper, a thermographic camera is used to capture the temperature distribution of an opened Infineon IGBT module FF600R17ME4 where each IGBT switch has three IGBT chips. The influence of temperature distribution on collector current sharing is then examined in both healthy conditions and bond wire lift-off scenarios. In this research, the critical temperature distribution is demonstrated experimentally at both chip and switch levels. The experimental results reveal that there are, depending on the collector current, 8 °C to 60 °C temperature difference at the chip level and 2 °C to 10 °C maximum temperature variation at the switch level. The severe temperature distribution impacts the collector current sharing less than 1 % variation under healthy conditions and 0.507 % at IC = 240 A upon the first bond wire lift-off. Other findings are that during homogeneous temperature distribution current densities are nearly similar per chip and less dependent on chip temperatures. Findings of this research have the potential to influence multichip Insulated Gate Bipolar Transistor (mIGBT) layout design. For example, having investigated the current density distribution at different operating points, it is recommended to increase the number of bond wires by 11 % for the chip placed in the middle for this particular module in order to increase reliability. Potential future research areas have also been identified.

Influence of temperature distribution on the foaming quality of foamed polypropylene composites

Abstract The foamed polypropylene (PP) composites were prepared by injection molding process. Fourier’s law and software were used to calculate and simulate the internal temperature distribution of PP composites, respectively, and the influence of the temperature distribution on the foaming quality of foamed PP composites was further analyzed. The result showed that the calculative and simulated results of temperature distribution in different thermal transfer directions had great reproducibility. In different isothermal planes, the temperature from the nozzle to the dynamic mold gradually decreased. The isothermal plane with a temperature of 370.36 K had a better foaming quality, average diameter of cell and cell density were 28.46 µm and 3.7 × 1010 cells·cm−3, respectively. In different regions of the same isothermal plane, the temperature gradually decreased from the center to the edge. The foaming quality in the region (c) at a temperature of 335.86 K was ideal, and the average diameter of cell and the cell density were 26.5 µm and 2.39 × 1010 cells·cm−3, respectively. This work could provide prediction for improving the foaming quality of foamed polyolefin composites.

Investigation on contact behavior of planetary roller screw mechanism considering thermal deformation

Previous thermal studies on planetary roller screw mechanism (PRSM) are mainly concentrated on frictional heat without the consideration of external thermal loads. However, the contact behavior of PRSM varies greatly during the operation process. In this paper, a calculating method for frictional heat of PRSM based on friction torque is proposed, and a transient thermal model is established to analyze the heat transfer of PRSM at multiple thermal conditions. After that, an analytical method is introduced to investigate the temperature, and the equations of its influences on the thermal deformation are derived. The influences of temperature distribution on the clearances and contact positions of the mating thread surfaces are studied as well. We found that the frictional heat, thermal resistance, and thermal loads can significantly alter the temperature distribution consistency. The results indicated that the load-bearing capacity of PRSM is greatly affected by the temperature differences between the planetary roller screw components. By allowing comprehensive thermal simulation, the proposed model can be utilized for PRSM optimization design.

An optimization model based on temperature field and series–parallel structure for battery‐package of a stratospheric airship

AbstractStratospheric airships are long‐endurance flight platforms that utilize renewable energy systems. The solar array in these systems cannot generate electricity at night; only an energy storage battery pack can be used to power the entire system. Therefore, accurate modeling and estimation of the output characteristics and operating conditions of battery packs have become the focus of current research. During the actual flight of an airship, uneven temperature distribution causes changes in the output characteristics and differences in the cell voltage of the battery packs. To address this problem, this study establishes an output characteristic model, series–parallel structure coupled with a temperature field model (SPTM), for a battery pack based on the series–parallel structure of a single cell. In addition, the influence of temperature distribution was considered in the model. Then, a flight verification test was conducted, and the test data and simulation data were compared. The average absolute error of the SPTM was maintained at approximately 0.61 V, which accurately reflected the output characteristics of the battery pack. The simulation model was then used to study the cell voltage difference under changes in the temperature distribution and demonstrate the relationship between the cell voltage difference and temperature difference.

Investigation on seawater freeze-thaw damage deterioration of marine concrete structures in cold regions from multi-scale

Influenced by the periodic tidal movement, the deterioration environment composed of the tide, seawater, air temperature (freezing) and sea temperature (melting) has become the key to the degradation of the marine reinforced concrete (RC) structures in cold regions. In view of this, the freeze-thaw cycles (FTCs) test of RC structures was carried out, and the damage distribution of concrete with seawater FTCs was tested. Subsequently, based on the temperature distribution, pore water crystallization law and critical saturation of concrete under seawater FTCs, the calculation method of FTCs damage was established from multi-scale, which the calculation results can well reflect the damage behavior of specimens with seawater FTCs. It is significant for the stiffness degradation of specimens with fewer FTCs, and the strength begins to decay for specimens with more than 50 FTCs. Moreover, there is an obvious FTCs boundary for concrete with 50 FTCs, and the depth of the FTCs boundary is close to the limit for RC specimens with 75 FTCs. Based on the discussion of the effects on FTCs, the influence of temperature distribution is much higher than that of critical saturation.

Study on the Influence of Temperature Distribution in the Optical Elements on the Surface Shape and Its Control Method during Full Aperture Polishing

Study on the Influence of Temperature Distribution in the Optical Elements on the Surface Shape and Its Control Method during Full Aperture Polishing

Temperature and Electric Field Distribution Characteristics of a DC-GIL Basin-Type Spacer with 3D Modelling and Simulation

The temperature properties of real-type direct-current gas-insulated transmission lines (DC-GIL) with a basin-type spacer were investigated by the finite element method in this paper. A horizontally installed model was established and the temperature distribution was obtained with a 3D model. The specific heat capacity and thermal conductivity of the spacer were measured and applied in the simulation. The results show that the temperature of the convex surface was slightly higher than that of the concave surface. With an increase in the SF6 pressure, the temperature of the spacer decreased, which can be attributed to the improvement of convection due to increases in the heat capacity per unit volume. With an increase in the ambient temperature, the temperature of the spacer increased linearly. The temperature difference between the inner and outer parts of the spacer increased with increases in the load current. Besides, an obvious increase in the surface electric field strength appeared under the influence of the thermal gradient compared to the results without the thermal gradient. Thus, special attention should be paid to the insulation properties of the spacer considering the influence of temperature distribution. This study evaluates both the thermal and insulation characteristics of the GIL along with the spacer under various conditions.

Mechanical behaviors of tunnel lining in uneven temperature field of high geothermal surrounding rock

Because of large temperature difference between inside and outside of tunnel lining in high ground temperature environment, thermal stress is easy to occur in the structure, which affects the stability of tunnel lining. In this paper, a three-dimensional thermo-mechanical coupled numerical model of rock stratum-tunnel is established based on a tunnel project with high geo-temperature, and the stress of tunnel lining under high geo-temperature environment is calculated and analyzed, the influence of temperature distribution on lining stress is analyzed. The results show that the principal stress and surrounding rock pressure increase with the increase of temperature at the initial stage of lining. When the temperature field is not uniform, the stress concentration is easier at the corner of the initial support of the high temperature side. When the temperature difference between the left and right sides of the lining is constant, the surrounding rock pressure ratio between the high temperature side and the low temperature side is basically the same. However, the pressure difference of surrounding rock increases with the increase of the initial temperature value. Therefore, the unfavorable temperature field distribution of surrounding rock should be carefully handled in tunnel design and construction. The research results of this paper will provide some reference value for the design and construction of similar tunnel with temperature and heat damage in highland.

Analyzing the Thermal Post-Buckling of Composite Plate Containing an Elliptical Cut-Out Using a Particle Semi-Energy Method

In this research, nonlinear thermal buckling and post-buckling behaviors of composite plate with the circular/elliptical cut-out are investigated using particle semi-energy (PSE) method. The semi-energy method is based on the solution of compatibility equation via an Airy force function and out-of-plane displacement function. The unknown parameters of these functions are determined by minimizing the potential energy. The integral of potential energy are replaced with summation of particles energy at perforated plate. The cut-out is modeled easily using these particles. The advantages of this method are easily cut-out modeling by particles and proposing just one of the displacement fields (i.e. out-of-plane). Based on the results, there is a good agreement (1.25%) between the post-buckling loads derived from PSE of this paper and experimental test of other literature. The accuracy of the finite element method (FEM) is 7.5% with respect to experimental test. The influences of temperature distribution, the cut-out size and elliptical cut-out rotating on post-buckling load and deflection of perforated plate are investigated.

Thermal Analysis and Impart of Temperature Distribution on the Performance of Additive Manufactured Titanium Alloy Based Composite Coatings

Finite element numerical analysis can be used to solve problems of boundary values. The accuracy of model is depended on the meshing refinement. In aerospace industry, finite element analysis has been used by several researchers to know the influence of temperature distribution on the performance of additive manufactured component parts. Accuracy is better with finer mesh. Complex nature of the additive manufacturing process due to rapid heating and cooling made many researchers to adopt numerical investigation which is made easier than the experimental method. Proper modelling of the process must be thoroughly done for the numerical modelling results to be analyzed. The experiment of ternary titanium alloy of Ti-Al-Si-Cu was carried out with cladding machine of 3000 Watts (CW) Ytterbium Laser System (YLS-2000-TR). This machine is situated at the National Laser Centre in the Council of Scientific and Industrial Research (NLC-CSIR). The characterization was done using the standardization ASTM E3-11 procedure. The results shiw the impart of temperature distribution on the dendritic arm spacing in the microstructures. The rate of cooling imparts on the space between the dendritic arms. The more the space, the more the influence on the coating’s properties

Analysis of Influence of Temperature Distribution in Spectral Control of Excimer Lasers for Lithography on Output Spectra

Analysis of Influence of Temperature Distribution in Spectral Control of Excimer Lasers for Lithography on Output Spectra

Influence of temperature distribution on circular saw blade natural frequencies during cutting

When cutting wood, heat is generated in the cutting zone and in the gullet due to the friction between the teeth of the blade and the material that is being cut. Since the wood is hydrophilic, the saw blade cannot be cooled with liquids, as is usual when cutting metals. The only way to remove the heat from the source is by conductivity to the centre of the saw blade and then by convection into the air. This research presents an analytical model to calculate the natural frequencies of circular saw blades exposed to different temperature distributions. The model confirmed experimental findings of many authors, i.e. the heating of the saw blade cutting edge reduces its natural frequencies, the rate of the reduction depending on the temperature difference between the cutting edge and the rest of the blade and on the shape of the temperature distribution. In contrast, heating the centre of the saw blade increases its natural frequencies, the rate of increase depending on the temperature difference and the shape of the temperature distribution. With the presented model, the most favourable temperature distribution can be calculated from the point of view of the critical saw blade speed, which can be achieved by heating or cooling the centre of the saw blade.

Monte Carlo simulation of ceramic grain growth during laser ablation processing

A Monte Carlo (MC) model was used to simulate ceramic grain growth during laser ablation. The simulation was performed to elucidate the effects of temperature distribution on grain growth. The influence of temperature distribution on the grain growth exponent was also indicated. According to the grain growth mechanism, the grain growth process of Al2O3 ceramics with different laser powers (170 W, 210 W, 260 W) and the same time (0.2 s) was simulated. The result shows that ceramic grain growth can be well simulated by the MC method during laser ablation. Particularly, it was observed that grain size was larger in the central region than at the edge, and the laser damage mechanism was microcracks caused by coarse grains. It was also shown that the simulation results were consistent with the experimental results.

Influence of Temperature Distribution on Radial Growth of Compressor Disks

Abstract For the next generation of aero-engines, manufacturers are planning to increase the overall compressor pressure ratio from the existing values around 50:1 to values of 70:1. The requirement to control the tight clearances between the blade tips and the casing overall engine-operating conditions is a challenge for the engine designer attempting to minimize tip-clearances losses. Accurate prediction of the tip clearance requires an accurate prediction of the radial growth of the compressor rotor, which depends on the temperature distribution of the disk. The flow in the rotating cavities between adjacent disks is buoyancy-driven, which creates a conjugate heat transfer problem: the disk temperature depends on the radial distribution of the Nusselt number, which in turn depends on the radial distribution of disk temperature. This paper focuses on calculating the radial growth of a simplified compressor disk in isolation from the other components. Calculations were performed using steady one-dimensional (1D) theoretical and two-dimensional numerical computations (2D finite element analysis (FEA)) for overall pressure ratios (OPRs) of 50:1, 60:1, and 70:1. At each pressure ratio, calculations were conducted for five different temperature distributions; the distribution based on an experimentally validated buoyancy model was used as the datum case, and the results from this were compared with those from linear, quadratic, cubic, and quartic power laws. The results show that the assumed distribution of disk temperature has a significant effect on the calculated disk growth, whereas the pressure ratio has only a relatively small effect. Good agreement between the growth calculated by the 1D theoretical model and the FEA suggests that the 1D model should be useful for design purposes. Although the results were obtained for steady-state conditions, a method is outlined for calculating the growth under transient conditions.

Reduction of the Negative Impact on the Environment By Optimizing the Combustion Process in Diesel Engines

The article considers the problem of the negative impact of the exhaust gases of diesel internal combustion engines on the environment and human health. The types of organization of the ignition process and the process of fuel combustion in a diesel engine are considered. The reasons for the occurrence of increased particulate matter in internal combustion engines in exhaust gases are also described. The main factors affecting the delay of ignition are given. The main stages of soot formation in diesel internal combustion engines are described. The influence of temperature distribution in the jets of injected fuel and the dependence of emissions on the coefficient of excess air are considered. As a result, the main conclusions are given on ensuring the reduction of solid particles in the exhaust gases of diesel engines by optimizing the combustion process.

3D tritium transport analysis for WCCB blanket based on COMSOL

As one of the CFETR candidate blanket schemes, Water-Cooled Ceramic Breeder (WCCB) blanket is being designed and developed by Institute of Plasma Physics, Chinese Academy of Sciences. Considering the safe operation of blanket, especially the radioactivity of tritium, it is crucial to study the tritium performance in the blanket, such as inventory, permeation, tritium taken by purge gas and release, which can likewise provide information for study and design of Tritium Extraction System (TES) and Coolant Purification System (CPS). Based on Finite Element Method (FEM), a more accurate three-dimensional model is set up using COMSOL Multi-physics. The influence of temperature distribution and velocity field of breeder zones on tritium transport is considered in the modelling. Finally, the tritium inventory, tritium permeation, tritium taken by purge gas and tritium release out of the blanket are calculated as well as the sensitivity analysis is conducted.

Effects of pressure and hydrogen addition to methane on the temperatures within a pressurized cylinder during the vehicle refueling of HCNG

Temperature increase in vehicle cylinder during the fast filling process keeps arousing the interest of many researchers. In this paper a new fuel consisting of hydrogen enriched natural gas called “HCNG”, and the influence of temperature distribution and elevation in HCNG tank were studied. A two-dimensional axisymmetric computational fluid dynamics (CFD) model for fast filling of HCNG vehicle cylinder of 150-L is established. The simulation is based on the standard k-ε turbulence model, and a real gas state equation is considered to evaluate the properties of the HCNG. The numerical simulations were performed with hydrogen mole fraction of 0%, 8%, 15% and 20%; the results show clearly the effect of the addition of hydrogen in methane. The increase in the concentration of Hydrogen is observed to be leading to a temperature increase.

Grasp of the influence of temperature distribution in the tube simulating a gas turbine combustor on acoustic boundary conditions

Grasp of the influence of temperature distribution in the tube simulating a gas turbine combustor on acoustic boundary conditions

Analysis of temperature distribution in shell mould during thin-wall superalloy casting and its effect on the resultant microstructure

This work focuses on the influence of temperature distribution in a shell mould during investment casting of thin wall parts on macrostructure, chemical composition of microstructural constituents and γ/γ′ misfit parameter. A reduction of production costs is associated with the optimization of precision casting technology of aircraft engine critical parts, including control of the solidification front in thin-walled castings of nickel superalloys.Appropriate lost-wax casting parameters lead to the creation of coarse grained structure, desired for high-temperature service applications. As a result of non-equilibrium solidification, substantially large chemical inhomogeneities in the dendrite core and interdendritic spaces are formed. Interdendritic spaces are occupied by constituents formed as a consequence of segregation of alloying elements, namely eutectic islands γ/γ′, borides, carbides, and an intermetallic compound of Ni and Zr. Dendrite cores consist of cubic-shaped γ′ precipitates surrounded by Ni-rich γ channels. Low lattice misfit influences cubic morphology of γ′ precipitates, which is favourable for jet engine application because it can guarantee good creep resistance.

Improving the spectral measurement accuracy based on temperature distribution and spectra-temperature relationship

Temperature is usually considered as a fluctuation in near-infrared spectral measurement. Chemometric methods were extensively studied to correct the effect of temperature variations. However, temperature can be considered as a constructive parameter that provides detailed chemical information when systematically changed during the measurement. Our group has researched the relationship between temperature-induced spectral variation (TSVC) and normalized squared temperature. In this study, we focused on the influence of temperature distribution in calibration set. Multi-temperature calibration set selection (MTCS) method was proposed to improve the prediction accuracy by considering the temperature distribution of calibration samples. Furthermore, double-temperature calibration set selection (DTCS) method was proposed based on MTCS method and the relationship between TSVC and normalized squared temperature. We compare the prediction performance of PLS models based on random sampling method and proposed methods. The results from experimental studies showed that the prediction performance was improved by using proposed methods. Therefore, MTCS method and DTCS method will be the alternative methods to improve prediction accuracy in near-infrared spectral measurement.