Numerical Simulation of Temperature Field and Thermal Stress Field of Work Roll During Hot Strip Rolling

Based on the thermal conduction equations, the three-dimensional （3D） temperature field of a work roll was investigated using finite element method （FEM）. The variations in the surface temperature of the work roll during hot strip rolling were described, and the thermal stress field of the work roll was also analyzed. The results showed that the highest roll surface temperature is 593 ℃, and the difference between the minimum and maximum values of thermal stress of the work roll surface is 145.7 MPa. Furthermore, the results of this analysis indicate that temperature and thermal stress are useful parameters for the investigation of roll thermal fatigue and also for improving the quality of strip during rolling.

Imitation design of temperature field in coloring hot dip galvanization process

Colors were generated by preferential oxidation of the metals in coloring hot dip galvanization process, and the evolution of temperature field during cooling after hot dip would be responsible for the coloration results directly. The influences of bath temperature and velocity of steel strip moving on temperature field of the strip were calculated in continuous coloring hot dip galvanization process by means of the ANSYS/Thermal module. The factors were considered including convection heat transfer, latent heat during cooling, and heat radiation in calculation. The effects of temperature field on coloration of sheet steel samples were investigated.

EMF of Hot Charge Carriers Arising at the p-n-Junction under the Influence of the Microwave Field and Light

It is shown that the increase in the current of an asymmetric p-n-junction, caused by perturbation of potential barrier height and increasing recombination current in a strong microwave field, is suppressed by light generated photo carriers, leading to the displacement of current-voltage characteristics of p-n-junction into the direction of smaller current values.

The Theoretically Studies and Field Testing of Self-Insulation Exterior Wall in the Hot Summer and Cold Winter Zone

The energy efficiency design of the exterior wall in the buildings of the hot summer and cold winter zone of China should consider the heat prevention in summer and the heat insulation in winter. The self-insulation of the exterior?wall is a more feasible design to satisfy the energy efficiency of buildings in the?zone. However, the systematic research is urgently needed for the self-insulation of the exterior wall in the hot summer and cold winter zone of China. The paper tested the thermal performance of the common non-clay materials such as shale sintered hollow brick, sand autoclaved aerated concrete block, etc. by means of indoor experiments. The energy efficiency effect of the common materials was verified using dynamic calculation soft PKPM and several constitutions of exterior wall with different main bricks and insulation materials on the heat bridge were simulated, too. Besides, the tests of the thermal performance of exterior wall in real constructions were carried out to testify the practical effect of the recommended constitutions of exterior wall with different main bricks and insulation materials on the heat bridge. The conclusions are: the physical and thermal properties of the six non-clay wall material are better than the clay porous brick;the thermal performance of the non-clay brick can be improved obviously through the rational arrangement of the holes;shale sintered hollow brick after increasing the holes and rationalizing the hole arrangement and sand autoclaved aerated concrete block are recommended for buildings in the hot summer and cold winter area of China. The dynamic calculation results show that the thermal performances?of the non-clay materials are all satisfied with the energy efficiency;The heat transfer coefficient of the exterior wall with composition?③,?in which?the main wall was sand autoclaved aerated concrete block and the material on the heat bridge was sand autoclaved aerated concrete plate, is the smallest among the three recommended compositions.

Numerical Simulation for Hot Dry Rock Geothermal Well Temperature Field

Study on temperature distribution simulation during cementing of hot dry rock (HDR) geothermal well is rare. It has important guiding significance to simulate the construction process of temperature distribution of hot dry rock on site construction. Based on numerical simulation of HDR considering heat-fluid-solid coupling, the influence of temperature distribution on well cementing is analyzed when the drilling fluid cycles and reaches stable state, respectively, and when the cement slurry is injected during the cementing process. It is found that the seepage at the well bottom accelerates the flow velocity of wellbore;the stable temperature change is less than the cyclic temperature change;and the upper and lower temperature variation of the stratum is greater when the cement slurry is injected. Therefore, as to cement retarder involved, the influence of temperature variation on concretion should be considered during cementing of the hot dry rock geothermal well.

Breakdown Electric Field of Hot 30% CF_3I/CO_2 Mixtures at Temperature of 300–3500 K During Arc Extinction Process

We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function （EEDF）, which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend （SST） condition. During the insulation recovery phase, the hot CF3I/CO2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction （90.3 Td, 1 Td=10-21 V.m2） is only 38% of the original value before arc （234.9 Td）. The adverse insulation recovery ability of CF3I/CO2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.

便携式锂钾分析仪现场测定热泉水中的锂

锂是绿色能源和轻质合金的理想原料,作为一种重要的战略性资源而备受各国重视。热泉水中富含锂,储量可观,然而热泉水主要分布在西藏、云南等偏远地区,样品运输与实验室测试成本高、效率低,锂资源勘查急需现场分析技术的支持。热泉水一般含有较高浓度的钠、钾等元素,基体效应显著。本文利用自主研发的便携式锂钾分析仪,搭配负性滤光片,选择锂的分析谱线波长670.78nm,通过优化测量条件,建立了标准曲线法与标准加入法现场测定热泉水中锂元素的分析方法。实验结果表明,当电解质是体积分数为1.5%的盐酸,工作电流为70mA,进样流速为3.0mL/min时,锂检出限为4.07μg/L,相对标准偏差(RSD)为1.03%。对热泉水样品进行加标测试,加标回收率为81.6%~115.9%。当热泉水样品基体组成较简单时,直接采用标准曲线法即可获得较准确的分析结果;当样品基体组成较复杂或者基体浓度高时,采用标准加入法可有效地减小基体效应,获得的分析结果相对更准确。本方法适用于不同类型基体的热泉水中锂含量的分析测试。

亚声速可压缩流场叶片边界层热线测速方法研究

为了能够开发一种简单有效的亚声速可压缩流场叶片边界层速度测量方法,从而为叶型设计和相关数值研究工作提供支撑,本文围绕热线风速测量技术,针对可压缩流场密度变化对热线标定结果的影响,以及实际测量中速度、密度耦合而无法直接获取的问题,通过理论分析,提出了适用于边界层测量的恒定压力热线标定方法和引入叶表稳态静压进行速度解耦的方法,并对所提出方法的主要误差进行了分析评估。在此基础上进行了热线标定和边界层速度测量试验验证,明确了恒定压力热线标定数学模型系数随压力的线性变化规律,同时针对温度非线性影响提出了一种基于过热比调整的修正方法,该方法能够将约13℃的温度偏差对热线电压的影响降低到1%以内,进一步简化了恒定压力热线标定流程,结合基于叶表稳态静压的速度解耦方法,为亚声速可压缩流场叶片边界层瞬态速度测量提供了一种简单可行的高频响测速方法。

基于密度场热点探测模型的传统村落空间分布与影响因素——以中国西南地区为例

传统村落是中国农耕文明留下的最大遗产和国土空间规划的重要组成部分,具有极高的研究价值.针对以往研究在分析传统村落空间分布时,多以离散的要素视角分析,难以获取确切的热点值且存在缺乏层级结构分析的不足.鉴于此,援引和构建密度场表面模型和热点等级探测模型,以中国西南地区2174个传统村落为例,提取传统村落热点,识别其空间分布模式和等级,归纳其空间结构,并进行影响因素分析.结果表明:①密度场表面模型和热点探测模型能有效实现从离散点到连续场的转变,能够从较大尺度范围及较小样本量中提取、识别及表达地理对象的不同形态和层级结构.②传统村落案例分析中,空间位置上具有明显的省级地域性、差异性,整体呈现出“东南密—西北疏”的空间格局;热点形态上呈现“多核多片”场形结构;热点数量随等级降低而增加,热点等级越高代表传统村落的空间分布越趋于集聚;省级尺度上等级热点分布不均衡,多分布于云南、四川两省;市级尺度上,等级较高的热点趋于分布在贵州东南部的黔东南苗族侗族自治州、铜仁市及云南保山市.③传统村落的形成及等级热点分布受自然与人文等众多影响因素的多重约束及共同影响.文末从推进乡村振兴和丰富空间分析定量方法作出讨论.

高导热环氧复合材料干式电抗器热点温升的仿真研究

干式电抗器的稳定运行影响新型电力系统的输电可靠性。干式空心电抗器包封材料整体由浸有环氧树脂的玻璃纤维丝经高温固化而成。本文采用多物理场耦合有限元方法,考虑干式空心电抗器的包封材料热导率对其热点温升的影响,建立了环氧复合材料的COMSOL微观仿真模型和外电路约束下的干式空心电抗器电-磁、流-热耦合计算模型。将电磁场下的损耗作为热源计算温度场与流场分布,研究在25℃环境温度下常规/高导热环氧复合材料对干式空心电抗器热点温升的影响规律。结果表明:高导热环氧树脂对复合材料热导率的提升效果显著;包封材料本体及周围空气温度场区域中热点温升最大值为103.75℃,出现在内部第4层包封材料的上端处;不同热导率的复合材料对降低干式电抗器的热点温升有明显差异,其中干式电抗器在高导热环氧树脂复合材料下的热点温度降低了7.55℃。

基于相场法的深层干热岩储层水力压裂模拟研究

为认识深层干热岩储层水力裂缝起裂与扩展规律,基于相场法建立了流−固−热耦合裂缝扩展数值模型,分析了干热岩储层水力压裂裂缝扩展力学行为,研究了温度、排量及天然裂缝等因素对水力裂缝扩展的影响。结果表明,基于相场法建立的流−固−热耦合裂缝扩展数值模型判别准则简单,计算准确;干热岩储层水力压裂过程中,热应力呈现为拉应力,有助于增加裂缝开度,对裂缝扩展起辅助作用;压裂液与地层温度差越大,排量越大,热应力影响效果越显著。水力压裂裂缝遇到天然裂缝后会沟通并开启天然裂缝,再次起裂时受地应力与天然裂缝控制。研究结果可为深层干热岩储层水力压裂提供参考。

射频联合热风加热对玉米籽粒中黄曲霉毒素B1降解及玉米品质的影响

为研究射频-热风联合处理玉米中的黄曲霉毒素B1(aflatoxin B1,AFB1)降解效果,分析不同初始水分质量分数(19.05%、22.25%、25.55%)、射频加热温度(55、65、75、85℃)和加热持续时间(10、15、20、25 min)对玉米籽粒中AFB1降解效果及玉米品质的影响。结果表明:射频-热风联合处理可有效降解AFB1,在高水分含量下,加热温度和时间一定,初始水分含量越高,AFB1残留量越高;初始水分含量一定,随温度增加和时间延长,AFB1残留量随之减少,且加热持续时间对降解效果的影响大于加热温度;射频-热风联合处理玉米籽粒过程中,对其品质有一定影响,随温度升高和时间延长,与对照组相比,蛋白质、脂肪含量无显著差异(P>0.05),黏度系数显著降低(P<0.05);低场核磁共振分析表明,射频加热过程中水分迁移效果明显,且水分迁移特性与玉米的糊化特性、蛋白质、脂肪含量显著相关(P<0.05)。

汽车半轴热锻模工况仿真及机器人电弧增材制造路径生成

为了确定热锻模具修复方案,使用有限元仿真软件模拟汽车半轴摆碾成形过程,生成机器人电弧增材制造路径。当连锻次数达到20次后,模具进入热平衡状态,中心圆台表层温度稳定在788℃,表层与540℃等温线相对深度约为28mm,应力场510MPa以上的模具增材层约为26.3mm,确定使用温度场划分模具增材制造区域。利用MATLAB提取540℃以上的点云部位,逆向建立3D模型,进行路径规划并在焊接机器人上运行。

外置式散热模块对配电变压器热点温升的影响

对于电网季节性过载引起的配电变压器温升过高情况,文中提出在油浸式配电变压器的散热片上安装外置式散热模块强化变压器散热能力,以降低热点温升。为验证该方法的可行性,以一台S13-M-200/10型配电变压器为研究对象建立三维模型,在变压器模型的散热片上建立外置式散热模块。改变散热模块建立的位置与数量从而形成4个不同计算模型。通过有限体积法计算4个模型在不同负载状态下的热点温升。对部分仿真结果使用短路法温升试验验证,仿真与计算误差小于3 K。试验与仿真结果表明合理的安装外置式散热模块可以使油浸式配电变压器的热点温升降低10 K左右,为配电变压器的温升降低提供一种新的思路。

门槛加强梁热冲模冷却水道数值模拟及参数优化

以热冲压门槛加强梁零件为例,建立热冲模冷却系统的流场和温度场的有限元模型,利用模拟软件结合正交试验设计方法,分析了高强钢热成形过程中温度场分布特征。结果表明:热冲模冷却水道的直径、水道到工作表面的距离以及水道之间的距离都会影响热冲模的冷却效果,结合实际生产因素,对热冲模冷却水道参数进行了优化。

New Breakdown Electric Field Calculation for SF6 High Voltage Circuit Breaker Applications

The critical electric fields of hot SF6 are calculated including both electron and ion kinetics in wide ranges of temperature and pressure, namely from 300 K up to 4000 K and 2 atmospheres up to 32 atmospheres respectively. Based on solving a multi-term electron Boltz- mann equation the calculations use improved electron-gas collision cross sections for twelve SF6 dissociation products with a particular emphasis on the electron-vibrating molecule interactions. The ion kinetics is also considered and its role on the critical field becomes non negligible as the temperature is above 2000 K. These critical fields are then used in hydrodynamics simulations which correctly predict the circuit breaker behaviours observed in the case of breaking tests.

Analysis of the thermal profile of work rolls in the hot strip rolling process

A 2-dimension axisymmetric model was developed by the finite-differencemethod, which can be used to predict the transient temperature field and thermal profile of workrolls in the hot strip rolling process. To demonstrate the accuracy and reliability of the solutiondeveloped, the calculation results were compared with the production data of a 1700 mm hot striprolling mill and good agreement was found between them. The effect of strip width and roll shiftingon the thermal expansion of the work rolls was studied. It is found that the strip width has markedeffect on the efficient thermal crown. Initially, when the rolling strip changes from narrow towide, a bigger efficient thermal crown can be quickly achieved; afterwards, when the rolling stripchanges from wide to narrow, not only the influence of uneven wear can be reduced but also theexcessive efficient thermal crown can be avoided. It is also found that the work roll shifting has adeterminate but not obvious effect on the reduction of the efficient thermal crown, and will makethe strip shape unstable without being used properly.

不同宽长比的柔性LTPS TFT的电应力可靠性

为了研究不同宽长比的柔性低温多晶硅薄膜晶体管(LTPS TFT)的电应力可靠性,测试了器件的I-V特性,以表征器件在强电场直流应力下由于自热效应和热载流子效应带来的电学性能退化。通过瞬态电流法表征了器件在强电场直流应力下的时间常数谱,并对其产生的新陷阱进行定位,分析了产生陷阱的内在机理。结果表明,在相同的强电场直流应力下宽长比为3/2.5的器件,其电学参数变化最大,自热效应以及热载流子效应带来的影响也最大。自热效应导致器件性能退化的主要原因是较大的栅源电压导致Si/SiO2界面处和栅氧化层中的陷阱增多,而热载流子效应导致器件性能退化的主要原因则是由于较大的漏源电压使得漏极晶界陷阱态密度急剧升高。

Numerical simulation of hot stamping of side impact beam

Ls-DYNA software is adopted to conduct research of numerical simulation on hot stamping of side impact beam to calculate the temperature field distribution,stress field distribution,forming limit diagram(FLD) figure,etc.in the course of hot stamping so as to predict and analyze the formability of parts.ProCAST software is employed to conduct research of numerical simulation on solid quenching course concerning hot stamping to calculate temperature field distribution of tools and component of multiple stamping cycles.The results obtained from numerical simulation can provide significant reference value to hot stamping part design,formability predication and tools cooling system design.

Quantitative Analysis of the Outdoor Thermal Comfort in the Hot and Humid Summertime of Shenzhen, China

Outdoor thermal comfort has always been a major issue due to its irreplaceable role in maintaining good health and energy use. Thus,quantitative analysis of outdoor thermal comfort and discussions on influential factors seem very necessary to achieve the climate-conscious urban design. Therefore,an outdoor thermal comfort questionnaire survey and the simultaneous field measurement were conducted in six different places during the hot and humid summertime in Shenzhen. The results show that the overall weather conditions during the investigation can be expressed with high temperature and high humidity with strong solar radiation. The micro-meteorological parameters of six test sites vary greatly due to their different regional spatial layouts.Moderate range of air temperature( Ta) is between 28 to 30 ℃ while that of relative humidity( RH) mainly concentrates in 60%-70% with the thermal sensation votes. The main influential factors impacting outdoor thermal comfort are obtained and Tahas the greatest effect. The overall thermal comfortable ranges in Shenzhen are expressed by the range of 28. 14-32. 83 ℃ of PET and 24. 74-30. 45 ℃ of SET*. With the correlation analysis between the characteristic parameters of regional spatial layout and thermal climate and thermal comfort,it reveals that increasing the coverage ratio of water and green space( S) helps lower Taand increase RH. The global solar radiation( G) has a significant negative correlation with the height of buildings( H) and a positive correlation with sky view factor( SVF). Overall,reasonable configuration of the regional spatial layout contributes to providing a thermal comfortable environment.