Numerical analysis of temperature distribution of plasma arc with molten pool in plasma arc melting

The relationships among the parameters that govern the plasma arc MR (melting and refining) process and the quality of the alloy melts are complicated. Only a simulation of the process can enable the process to be properly controlled and the right compositions to be achieved. The main purpose of this paper is to simulate the temperature distribution in the molten pool using the software FEMLAB. Numerical calculations were based on finite element analysis and the coupling of heat transfer, fluid flow and electromagnetic modules. The results of simulations are verified with the meniscus shape of liquid isothermal line in the solid ingot.     

LNG fires: a review of experimental results, models and hazard prediction challenges

A number of experimental investigations of LNG fires (of sizes 35 m diameter and smaller) were undertaken, world wide, during the 1970s and 1980s to study their physical and radiative characteristics. This paper reviews the published data from several of these tests including from the largest test to date, the 35 m, Montoir tests.

Also reviewed in this paper is the state of the art in modeling LNG pool and vapor fires, including thermal radiation hazard modeling. The review is limited to considering the integral and semi-empirical models (solid flame and point source); CFD models are not reviewed. Several aspects of modeling LNG fires are reviewed including, the physical characteristics, such as the (visible) fire size and shape, tilt and drag in windy conditions, smoke production, radiant thermal output, etc., and the consideration of experimental data in the models. Comparisons of model results with experimental data are indicated and current deficiencies in modeling are discussed.

The requirements in the US and European regulations related to LNG fire hazard assessment are reviewed, in brief, in the light of model inaccuracies, criteria for hazards to people and structures, and the effects of mitigating circumstances. The paper identifies: (i) critical parameters for which there exist no data, (ii) uncertainties and unknowns in modeling and (iii) deficiencies and gaps in current regulatory recipes for predicting hazards.     

On the temperature distribution in the counter flow heat exchanger with multicomponent non-azeotropic mixtures

The influence of mixture composition on the temperature distribution in the counter flow heat exchanger used in mixture Joule–Thomson refrigerators is investigated in this paper. A perfect heat capacity matching between the supply and the return streams can be achieved by optimizing the mixture composition. The deeper reason is that in two-phase state the latent heat makes a very important contribution in the overall heat capacity for multicomponent non-azeotropic mixtures. The theoretical results are compared with experimental data; both theoretical and experimental results agree well with each other. The results show that the temperature profile as well as the locations of the pinch points is determined by the mixture compositions. Therefore, it is possible to get a perfect temperature distribution using optimal mixture. This becomes another criterion of the optimization of mixture composition.     

Control of substrate surface temperature in millisecond annealing technique using thermal plasma jet

Temporal variations of substrate surface temperature in scanning Ar thermal plasma jet has been investigated based on an analysis of transient changes in optical reflectivity. The accuracy of the temperature measurement has been evaluated to be 30 K at temperature around 1760 K. The maximum surface temperature (T_max) is controlled in the range from ∼ 960 to ∼ 1780 K with keeping the annealing duration (t_a) around ∼ 3 ms by changing the Ar gas flow rate (f) and distance between the plasma jet and the substrate (d) under a constant scanning speed (ν) of 500 mm/s.     

微小激光加工区辐射测温准确性的提高

利用辐射测温系统进行温度测量时,所测温度的准确性及分布细节会受多种因素的影响,使得实验测得的温度分布远远低于实际值,为了提高温度测量的准确性,提出了一种估计真实温度分布的新方法。这种方法主要包括:将原有探测器更改为带单模尾纤式探测器、减小光接收面面积、将原有的透镜更改为红外消像差透镜,最后利用图像复原技术中的—Lucy-Richardson算法求出最佳真实温度分布估计。其中前4个步骤有效的提高了测温分布细节,实验测得微小面元温度分布半宽值仅21μm,远远小于之前测得的半宽值;Lucy-Richardson算法则将温度分布中被点扩展函数卷积掉的高温部分复原回来,实验测得微小面元温度分布在复原后温度最高值高出复原前最高值近100℃。实验证明这种方法有效的提高了测温准确性。     

驻波热声发动机板叠温度分布的红外观察

为了深入研究热声板叠中的能量流动和分布,采用红外热像仪对自行设计搭建的驻波热声发动机板叠进行了温度场观测,重点分析了起消振过程中板叠的轴向和径向温度分布变化.实验结果表明:在起振时,板叠轴向中部的无量纲温度会出现突然升高并随之保持平稳.通过分析不同板叠安装角度下的板叠温度分布,首次发现自然对流会使起振前板叠的径向温度分...     

利用Matlab开发平台的炉膛火焰图像温度检测方法

介绍了目前炉膛火焰检测系统的技术特性及用于火焰检测的数字图像处理技术。通过对炉膛火焰温度的CCD数字图像检测方法可行性的分析，设计了用于监测炉膛温度面分布的试验系统；通过火焰图像象素RGB值与温度的对应关系，建立了火焰图像的温度场曲线，通过原理性试验初步验证了该技术的可行性。     

墙角火灾环境下钢构件温度分布及响应行为的实验研究

利用ISO9705标准火灾实验系统,模拟墙角火灾环境,以薄壁方管钢梁为研究对象,对钢构件在热、力耦合作用下的行为进行实验研究。对火灾的热释放速率与室内温度场,钢构件及其表面气体的温度、构件在火灾作用下的挠度进行测量,分析真实火灾下钢构件温升及温度分布的特点与火灾发展对构件挠度的影响。研究结果表明钢构件在长向上存在着很大的温差,而构件的挠度变化也并不对称,这说明以往研究中往往假设钢构件在长向上温度一致并不恰当,这种非均匀温度场对构件的行为有着重要影响,它使得构件高温区部分更易发生局部屈服而失效,在相同规模的     

A numerical study of the scalar field in turbulent round jet with co-flowing stream

The influence of co-flow on a turbulent binary gas mixing round jet is numerically studied using a first and a second order turbulence closure models. The objective of the study is to obtain a better understanding of the flow structure and mixing process in turbulent variable-density jets. Comparisons between recently published experimental results and mean mixture fraction, the scalar turbulent fluctuation, and the jet spreading rate, feature reasonably good agreements. It is mainly shown that the co-flow reduces the jet spreading rate, but on the otherhand increases the mixing efficiency.An erratum to this article can be found at     

干井式温度校验器校准方法的研究

干井式温度校验器被广泛应用于企业现场和计量实验室，为了评估其性能，就需要计量机构对干井式温度校验器进行校准。但目前我国还没有制订其校准的相关标准和规范。现根据干井式温度校验器的性能特点、测温原理和使用范围，参考国际上采用的校准指南对干井式温度校验器的校准方法进行了研究，主要内容包括温度偏差、温度稳定性、温度均匀性、散热效应和负载影响，并通过校准实例说明该校准方法是切实可行的。     

高压蒸汽灭菌器的温度分布

高压蒸汽灭菌做为目前重要的灭菌技术广泛用于各行各业,但是灭菌温场的分布鲜有报道。为了明确温场对灭菌效果的影响,参照国标的技术指标对灭菌过程的温场均匀性和温度波动性作了初步研究。以德国ebro生产的无线温度数据存储器为测温设备,在总结大量实验数据的基础上分析出影响温场的几个重要因素:装载量、残余冷汽团、温度控制器、温度探头位置,并对其影响温场的原理做了通俗易懂的阐述,且结合实际使用情况给出建议。     

层状火焰中透镜效应的研究

分析预混气体燃烧气流形成的层状结构,建立其分界面的模拟方程;用矩阵方法教育处光透射率和厚度灵敏因子,得到层状火焰透镜的性能参数;引进光学材料的规化热差系数和色差系数,建立无热差光学系统的方程,并提出了消除温度对其焦距影响的方案,结果表明：精细的火焰多层膜层结构的透镜效应研究对获得极准确的激光全息信息非常有益。     

The influence of temperature on integrated circuit failure mechanisms

Temperature is generally considered to be a key parameter in the design of electronic equipment, and cautions concerning temperature and its relationship to reliability are widely documented. While some studies suggest that temperature is the most critical stress influence on microelectronic device failures, the actual failure mechanisms have generally not been quantified in terms of whether a steady state temperature, temperature change, rate of temperature change, or spatial temperature gradient induced failure. In this paper, the influence of temperature on major integrated circuit failure mechanisms is discussed, with emphasis placed on those failure mechanisms which occur in the temperature range of -55°C to 125°C. This paper shows that no simple expression can adequately describe temperature as a failure accelerator for all integrated circuit failure mechanisms. In fact, a generic statement that can be attributed to temperature is lacking. This suggests that a much deeper level of insight into temperature dependencies is necessary to achieve reliable equipment and avoid unnecessary thermal design complexities. Thermal management in electronic equipment can involve additional costs and system complexities that can be of consequential importance, and temperature control should not be routinely employed without close study and justification.     

Measurement of the distribution of the temperature field of materials in microwave resonators of complex shape

The main problems that arise when measuring the temperature field of dielectric materials in microwave resonators of different shapes at a frequency of 2450 MHz are considered. The results of measurements of the temperature field distribution are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 56–58, June, 2008.     

立式开式陈列柜风幕送风速度对其温度分布影响的实验研究

实验研究立式开式陈列柜风幕送风速度对其温度分布的影响。实验结果表明，降低其内风幕的送风速度或提高其外风幕的送风速度，均能使风幕向柜内侧偏移，减少冷风幕的外溢，提高风幕封闭敞口的能力，改善陈列柜的性能。     

Shock structure deformation in plasma jet caused by strong magnetic field

The shock structure deformation in a plasma jet caused by a strong magnetic field was studied using an optical method. The plasma jet images in the enclosing vacuum chamber were taken with a digital single-lens reflex camera through a viewing window. Since the relative values of the measured light intensity are known to have a strong correlation with the number density of excited atoms, the vertical distribution of light intensity can be converted to a radial distribution of excited atom density using an Abel-inversion. The results of this conversion with a magnetic field were compared in the present experiments with those without the presence of a field. It is possible to obtain a smooth radial distribution of estimated number density using an approximate line. The density along the centerline increases obviously with the magnetic field. The minimal density point around the Mach disk was moved slightly upstream with the application of the field. The density distribution inside of the jet boundary was changed considerably by the application of the strong field. The jet boundary itself was not found to be affected significantly by the field although the boundary was found to be slightly contracted to the center axis with application of the field. It has been confirmed that the density distributions are mainly affected by the magnetic field at the corresponding location.     

粉末药型罩聚能射流形成过程中温度分布及影响分析

根据石油射孔弹的实际结构和几何尺寸,运用ANSYS/LS-DYNA-2D非线性动力学有限元分析软件,采用瞬态非线性的热耦合计算方式,对孔隙率为11.53%的铜药型罩射流形成过程中典型瞬态的温度场进行描述和分析;对多孔药型罩聚能射流的最高温度-时间曲线进行研究,并对射流自身是否产生熔化进行判断;对比了多孔药型罩与密实药型罩聚能射流轴线和外表面温度。结果表明:聚能射流轴线温度高,由轴线向外表面逐渐降低,最高温度先增大,11μs增到最大1 743K后减小,最后几乎不变,约为1 378K,多孔药型罩比密实药型罩聚能射流的温度高,延伸性能和稳定性能更好。     

粉末药型罩聚能射流形成过程中温度分布及影响分析

根据石油射孔弹的实际结构和几何尺寸,运用ANSYS/LS-DYNA-2D非线性动力学有限元分析软件,采用瞬态非线性的热耦合计算方式,对孔隙率为11.53%的铜药型罩射流形成过程中典型瞬态的温度场进行描述和分析;对多孔药型罩聚能射流的最高温度-时间曲线进行研究,并对射流自身是否产生熔化进行判断;对比了多孔药型罩与密实药型罩聚能射流轴线和外表面温度。结果表明:聚能射流轴线温度高,由轴线向外表面逐渐降低,最高温度先增大,11μs增到最大1 743K后减小,最后几乎不变,约为1 378K,多孔药型罩比密实药型罩聚能射流的温度高,延伸性能和稳定性能更好。     

用于测量柴油机气缸内碳粒浓度和火焰温度的光电系统

利用颗粒衍射原理,研制出一套用于测量柴油机气缸内局部瞬态碳粒浓度和火焰温度的光电测量系统。该系统采用分叉光纤,省去了一套复杂的光学分光组件。利用该测量系统对一台柴油机气缸内进行了相应测量,并分析了测量数据,结果表明活塞凹坑区的火焰温度和碳粒浓度相当高,在活塞的顶岸区,它们的循环变动很大。     

Numerical investigations on internal temperature distribution and refrigeration performance of reciprocating active magnetic regenerator of room temperature magnetic refrigeration

A two-dimension porous medium model for a reciprocating active magnetic regenerator (AMR) of room temperature magnetic refrigeration has been developed. The thermal diffusion effect, heat flux boundary effect and variable fluid physical properties are considered in the model. In the paper, we compare the numerical results of the porous medium model with the experimental data and the calculation results of one-dimension Schumann model to validate our model. Our model can simulate the operation of the reciprocating AMR effectively. With the present model, the internal heat exchange between the two phases is numerically investigated. The two dimensional temperature distributions of the magnetic refrigerant and the refrigeration performance of AMR are obtained, and the influence of the heat flux boundary effect and the variable fluid properties on them is discussed. AMR can achieve a maximum refrigeration capacity of 293.7 W with a corresponding coefficient of performance (COP) of 5.4.