薄板坯连铸结晶器铜板温度及热流密度分布

薄板坯连铸结晶器的传热过程直接影响到铜板的寿命,有必要研究薄板坯连铸结晶器的传热特征。为了研究薄板坯结晶器的热流密度,通过开发的结晶器温度监测软件检测了珠钢结晶器铜板的温度。根据在线实测的铜板温度以及薄板坯连铸机冷却参数,建立了薄板坯结晶器铜板传热模型,计算并验证了结晶器热流密度的分布函数,同时通过二次回归得出了结晶器热流密度与结晶器高度的关系式。结果表明,在宽度方向上铜板温度和热流密度的分布具有相似的规律性,距离弯月面越近,热流密度和温度的波动越大。弯月面处热流密度值大于4．2MW／m^2,是造成结晶器铜板被侵蚀的主要原因。     

基于热流密度分布模型的连铸倒角结晶器温度分布研究

基于热流密度分布模型,建立了全弧形板坯连铸机倒角结晶器窄面冷却水流动和铜板传热耦合的数学模型。采用多元回归的方法拟合得到描述连铸结晶器热流密度对结晶器高度的函数表达式。铜板表面沿拉坯方向的热流密度呈非线性分布,弯月面附近的热流密度先急剧增加然后迅速减小,在距离弯月面0.1 m处的热流密度达到最大值。模型计算结果表明,在结晶器距上口150～200 mm的铜板表面温度最高达到608～678 K,低于723 K的铬锆铜再结晶软化温度;尽管该区域铜板水缝的最高表面温度近420 K,但不影响整体传热。计算的铜板温度与热电偶测量值相吻合。     

环路热管双孔径分布毛细结构的研究进展

双孔径分布毛细结构因在高热流密度下的优异传热性能而被越来越多地应用在环路热管蒸发器中。本文总结了环路热管双孔径分布毛细结构的主要类型、形貌特征、制备工艺及内部传热过程;通过分析孔径分布、芯体厚度、蒸气层厚度及气液界面的薄膜蒸发,探讨了双孔径分布毛细结构的传热机理,并与单孔径毛细结构的传热性能进行了对比;最后综述了双孔径分布毛细结构主要热物性参数的计算模型及试验关联式。     

珠钢薄板坯连铸结晶器传热特征的研究

薄板坯连铸结晶器的传热过程直接影响到铜板的寿命，因此有必要研究薄板坯连铸结晶器的传热特征。根据在线实测的铜板温度以及薄板坯连铸机冷却参数，建立了薄板坯结晶器铜板传热模型，计算并验证了结晶器热流密度的分布函数。结果表明，宽度方向上铜板温度和热流密度分布具有相似的规律性，距离弯月面越近，热流密度和温度的波动越大；弯月面处热流密度值超过4．4MW／m^2，结晶器热面温度高于铜的再结晶温度，这是造成结晶器铜板被侵蚀的主要原因。     

二氧化硅纳米流体强化对流换热研究进展

随着半导体技术和电子技术的快速发展，高集成化和高性能化的微电子器件在航空航天、能源、医疗和汽车工业等领域发挥着越来越重要的作用。为了避免出现高热流密度引起的器件高温失效问题，对微电子器件进行有效热管理是非常关键的。传统的风冷和液冷技术不仅功耗高而且散热效率低，严重影响了器件的稳定性和可靠性。近年来，国内外研究者提出了多种新型被动式和主动式强化换热技术。其中，纳米流体强化换热技术由于成本低、操控灵活和形式多样性的特点，受到了广泛的关注。特别是对于二氧化硅纳米颗粒，良好的机械和化学稳定性、丰富的结构形式和多样化的合成方法等优势引起了研究者极大的兴趣。目前，二氧化硅纳米流体在导热、对流和辐射传热方面都有显著的强化性能。以电子器件液冷技术为背景对二氧化硅纳米流体在强化对流换热的研究进展进行了系统综述，首先介绍了二氧化硅纳米流体的性质和制备方法，然后讨论并总结了二氧化硅纳米流体在单相对流（自然对流和强制对流）和相变对流（池沸腾和流动沸腾）领域的研究现状，最后强调二氧化硅纳米流体对流换热技术存在的问题以及未来发展的方向，为建立高性能纳米流体液冷换热技术体系提供相应的思路和参考。      

ASP连铸结晶器铜板热流和温度的研究

根据在线实测的铜板温度以及ASP(Angang Strip Production)板坯连铸机冷却参数,建立了ASP板坯结晶器(高1 000 mm,铸坯断口面170 mm×2 000 mm)铜板传热模型以计算结晶器热流密度的分布函数和得出结晶器热流密度与结晶器高度的关系式。结果表明,铜板温度和热流密度的分布具有相似的规律性,结晶器内、外弧铜板宽度方向上中心和角部的热流波动分别约为400 kW/m²和200 kW/m²,其温度差分别约为30℃和20℃。     

包晶钢宽厚板坯连铸结晶器的热流密度与热行为

基于热电偶实测温度,建立了包晶钢宽厚板坯连铸结晶器有限元传热模型和热流密度非线性估算模型.应用模型反算获得包晶钢宽厚板坯结晶器的热流密度,在与热平衡计算得到的平均热流密度进行比较后,阐述了模型的有效性,并分析了实际生产条件下结晶器铜板的温度分布规律.结晶器宽面和窄面的平均热流密度分别为1.141和1.119 MW·m-2.温度在靠近结晶器背面呈波浪形分布,最大温差为29.6℃,然而在远离背面位置,温度变化平缓.随距弯月面距离的增加,温度呈降低趋势,然而在距结晶器出口附近出现回温现象.同时宽厚板坯连铸结晶器的热流密度和温度分布均有别于传统板坯连铸.      

连铸坯凝固过程中传输现象基础知识系列讲座：第十八讲 二冷区的凝固传热

介绍了连铸坯在二冷区凝固传热的传热方式，传热系数和影响二冷区传热的因素，同时也介绍了二冷区传导热流的计算公式以及用来表达传热系数与水流密度之间的经验公式。     

粉末冶金钛合金制备技术研究进展北大核心

钛及其合金因密度低、强度高、耐蚀性好、生物相容性好等特点被广泛应用于航空航天,汽车舰船,石油化工,生物医疗等领域。本文主要针对钛及其合金的粉末冶金制备技术研究现状进行了介绍,从制粉和成形致密化两个方面介绍了国内外的制备技术,并且指出粉末冶金钛合金未来发展的关键是微细低间隙钛粉的制备,大尺寸坯料的制备和高性能烧结坯的制备。     

粉末冶金钛合金制备技术研究进展

钛及其合金因密度低、强度高、耐蚀性好、生物相容性好等特点被广泛应用于航空航天,汽车舰船,石油化工,生物医疗等领域。本文主要针对钛及其合金的粉末冶金制备技术研究现状进行了介绍,从制粉和成形致密化两个方面介绍了国内外的制备技术,并且指出粉末冶金钛合金未来发展的关键是微细低间隙钛粉的制备,大尺寸坯料的制备和高性能烧结坯的制备。     

高通量换热管与烧结型高通量换热管性能介绍

高通量换热管是管壳式换热器强化传热技术深入研究下的产物。通过介绍汽化核心和汽泡形成阐释其强化传热原理。烧结型高通量换热管是多种高通量换热管型中具有代表性的一种,在有相变的沸腾工况下,其提高传热效果已被证实,但强化程度说法不一。通过蒸发池沸腾测试试验,比较公司自行研发的烧结型高通量换热管和普通光管的测试结果,探究高通量换热管的真实传热性能,对高通量换热器设计及高通量换热管的研发提供参考建议。     

含高分压不凝性气体的蒸汽在倾斜管内的凝结换热

设计建立了一套以水为工质的分离式热管系统实验台，系统冷凝端采用水冷套管式换热器。在此实验台基础上研究了不抽真空，有大量不凝性气体空气存在于分离式热管的蒸汽凝结放热问题。测定了不同的蒸汽入口温度、循环蒸汽流量、冷却水进口温度及流量四种情况下混合气体在圆管内凝结放热的情况，分析了这些参数对换热过程的影响。     

分形微通道换热过程强化研究进展

随着微纳制造技术的快速发展,微电子芯片、微反应器和微燃料电池等微型器件受到了研究者越来越多的关注。微型器件的应用不仅对加工工艺和材料具有较高的要求,而且需要高效的热管理来维持其性能。特别是对于高集成度和高频化的高性能微电子芯片而言,超高的热流密度不仅会严重制约芯片的性能,而且会显著影响芯片的寿命和可靠性。鉴于传统的风冷和液体单相对流换热冷却方式无法满足散热需求,具有高换热系数的微通道换热技术成为解决微型器件散热问题的重要途径。然而,常规的微通道换热技术普遍存在着高流动阻力和非均温性的难题,限制了该技术的实际规模化应用。近年来,研究者开发出一系列新型的分形微通道技术用于换热过程强化。本文系统总结了不同类型的分形换热微通道（包括Y、H、T、Ψ、康托、科赫等分形结构）,并对各分形微通道的原理和性能进行了着重介绍,最后对分形微通道换热的现存挑战和未来发展方向分别进行了分析和展望,以期为换热过程强化的发展提供新的研究思路。      

Heat Withdrawal in the Mold in Continuous Casting of Steel. Review and Analysis

Two principal methods are used to investigate the heat transfer in the continuous casting mold. The direct way is to measure cooling water temperatures, mold wall temperatures, strand temperatures and shell thickness in actual operation, and then deduce from these data the correlations for heat flux densities. The other way is to investigate the “unit operations” of heat transfer theoretically or experimentally in the laboratory, viz. heat transfer through a layer of casting flux or of gas, and heat transfer in a copper wall cooled on one side by water. The results obtained in this approach can then be used to explain the data determined with the direct method and to optimize the heat transfer behaviour of the mold in the machine. In the first part of this paper some unit operations are discussed and engineering formulae are given for computation of the heat resistances of the gap and the copper/water system. In the second part of the paper the available operational data on heat flux density are analysed. Algorithms are presented for computation of local and average heat flux density as functions of casting speed, carbon content of the steel and composition of the casting flux. Finally, values of shell thickness are computed with the correlation for heat flux density and are compared with the measured data.     

Monoamines, monoamine metabolites, neuron specific enolase and myelin basic protein concentrations in cerebrospinal fluid of resuscitated patients

The objective of this study was to evaluate manometric temperature measurement as a non-invasive method of monitoring product temperature during the primary drying phase of lyophilization. This method is based on analysis of the transient response of the chamber pressure when the flow of water vapor from the chamber to the condenser is momentarily interrupted. Manometric temperature measurements (MTM) were compared to product temperature data measured by thermocouples during the lyophilization of water, mannitol, lactose and potassium chloride solutions. The transient pressure response was mathematically modeled by assuming that four mechanisms contribute to the pressure rise: 1) direct sublimation of ice through the dried product layer at a constant temperature, 2) an increase in the temperature at the sublimation interface due to equilibration of the temperature gradient across the frozen layer, 3) an increase in the ice temperature due to continued heating of the frozen matrix during the measurement, and 4) leaks in the chamber. Experimental transient pressure response data were fitted to an equation consisting of the sum of these terms containing three variables corresponding to the vapor pressure of ice, product resistance to vapor flow, and the vial heat transfer coefficient. Excellent fit between the mathematical model and the experimental data was observed, and the value of the variables was calculated from the measured transient pressure response by a least squares method. The product temperature measured by MTM, which measures the temperature at the sublimation interface, was compared with product temperature measured by thermocouples placed in the bottom center of the vials. Manometrically measured temperatures were consistently lower than the thermocouple measurements by about 2 degrees C, this difference being largely accounted for by the temperature gradient across the frozen layer. The resistance of the dried product to mass transfer calculated from MTM was found to agree reasonably well with values measured by a direct vial technique. Product resistance was observed to increase with increasing solute concentration, and to increase continuously as the depth of the dried product layer increases for mannitol and potassium chloride. For lactose, product resistance increases continuously with thickness up to the onset of collapse, at which point the product resistance becomes essentially independent of depth. Scanning electron microscopy was used to explain this observation based on changes in morphology of the solid. The vial heat transfer coefficients obtained from regression analysis were on the order of 10(-3)-10(-4) cal.sec-1. degrees C-1; however, the scatter in the vial heat transfer coefficient data prevents the method from being used for accurate measurement of the vial heat transfer coefficient. The results of the study show that the manometric method shows promise as a process development tool and as an alternative method of in-process product temperature measurement during primary drying.     

高温低氧燃烧锅炉传热特性研究

介绍一种新型工业锅炉 -高温低氧燃烧锅炉 ,研究其传热特性。实验研究表明 :炉内燃烧火焰边界趋于消失 ,体积明显增大 ,火焰颜色变浅 ,无局部高温区 ,辐射传热得到强化。提高空气预热温度可加大炉气和水冷壁间传热。为开发推广新型工业锅炉奠定基础     

Combination of inverse problem and neural network for thermal behaviour calculation of mould process based on temperature measurements in plant trial

Abstract

Heat transfer between mould and strand has a critical influence on billet quality, caster productivity and operating safety. It is very important to obtain the correct distributions of temperature and heat flux, and many studies are made on the calculation methods of heat transfer between strand and mould, aiming to reduce the computation time and improve the calculation accuracy. In the present paper, based on measured data of temperature and heat flux during round billet continuous casting, the calculation method which combines the online measurement data and numerical simulation was investigated. Through identifying the local thermal resistance and its distribution between the mould and the strand by an inverse heat transfer model, the heat flux and shell thickness profiles were calculated. To avoid the iterative solution by inverse model, a faster alternative model using an artificial neural network was developed to predict the thermal resistance from the measured temperature. After training, there is an exact correspondence between the observed temperature values and the thermal resistance. The calculation results obtained by the combination of neural network and numerical simulation can correctly reflect the characteristics of non-uniform heat transfer around the mould circumference, which provides a worthwhile and applicable method for online calculation and visual technology of heat transfer and solidification in continuous casting mould.     

热流法计算高温炉内辐射传热

高温炉内的辐射传热是工业生产中常遇到的问题。过去，人们在应用热流法计算辐射传热时遇到了一定的困难，使计算结果与实际有一定的偏差。本文运用文献［１］中给出的新热流数学模型，开发出由新热流方程与能量方程相耦合的计算机程序，其中的比热流参数由线加热热源情况下计算得到。用该程序计算了实验室用马弗炉内的温度场，并且用热电偶实测了炉内的一些温度值，理论计算与实测值符合很好。     

大型环形加热炉用高效节能空气换热器的研制

在环形炉使用的空气换热器设计中采用了高效旋流器和单扭带插入件取代了光管,并利用数值计算方法对其进行了详细地仿真计算,使空气换热器的综合传热系数得到显著提高,得出了满足设计要求的最佳结构参数。采用SolidWorks三维设计软件和AutoCAD工程设计软件开发出新一代高效节能型空气换热器,并投入工程应用,效果良好,推广前景广阔。     

多头螺旋管换热过程的三维数值模拟

随着节能减排的生态发展理念深入人心,如何最大限度地提高能源的利用率,成为时下研究的热点．文中以多头螺旋管为研究对象,并以当量直径的光管作为基准管,运用有限元分析软件ANSYS对模型的传热过程进行数值模拟,得出了换热过程中温度场与流场的分布状况,而后结合传热学中的边界层理论和协同场理论对结果进行综合分析．结果表明：在等热流的情况下,多头螺旋管的换热性能明显优于光管,相对光管,多头管内流体的出口温升相对提高了2．6倍,出口速度相对下降50％;其特殊的内外凸筋结构,是强化传热的主要原因,同时,凸筋造成流体的有涡流动,也使得多头螺旋管管壁不易结垢．