螺旋扭曲扁管式换热管流体流动及传热特性的CFD仿真

从理论上分析了烟气余热回收装置螺旋扭曲扁管式换热管的机理。利用CFD软件,研究了螺旋扭曲扁管式换热管管程内流体流动及传热特性,并对换热管传热性能的影响因素进行探讨。结果表明:相同操作工况下,螺旋扭曲扁管传热性能强于直椭圆管、普通圆管;扭曲比在影响螺旋扭曲扁管传热性能中有最佳值;螺旋扭曲扁管在不同扁度及流动状态下,扁度及雷诺数越大,强化传热效果越好。     

双H型翅片管与螺旋翅片管传热性能的对比试验

对常用结构的双H型翅片管和螺旋型翅片管在不同流量和雷诺数条件下的传热性能进行了对比试验,得出了不同水流量下努塞尔数Nu与雷诺数Re的关系曲线和相应的传热准则关联式,并对其进行了分析对比。结果表明:在双H型翅片管的翅片节距与螺旋型翅片管的螺距相等的情况下,双H型翅片管的传热特性和阻力特性均优于螺旋翅片管。而螺旋型翅片管中螺距较大的管束的传热性能较好。     

交叉缩放椭圆管内污垢的数值模拟

从传热传质的角度建立交叉缩放椭圆管内CaCO3污垢形成过程的模型,通过数值方法进行求解,得到了温度场、速度场、以及CaCO3的浓度场,然后计算出CaCO3污垢的沉积率、剥蚀率和污垢热阻以及这些量随温度、浓度的变化规律.最后将模拟结果和实验结果进行对比,结果表明模拟结果与实验数据吻合良好.     

气升式反应器内流动与传质研究进展

综述近几年来气升式反应器内流动与传质研究成果.介绍气升式反应器结构上的改进以及操作条件等对气升式反应器内流动与传质的影响;揭示传质过程中各动力学模型;总结气升式反应器在生物、环境领域方面的应用研究进展.研究内容为功能性气升式反应器的设计和放大提供理论依据.指出今后的研究方向与重点是要探索各操作条件对气升式反应器性能的影响规律,同时必须结合其它领域研究成果、采用CFD模拟技术、实验流动测量技术等来开发高效新型气升式反应器.      

折流元件对气升式环流反应器性能的影响：Ⅱ.流动阻力,传热及传质

在模拟实验装置内,以空气和水为介质,进行了带有Ｋ型和Ｈ型折流元件的单相流和两相流的阻力和传热实验,以Ｎ２ａＣＯ３水溶液吸收ＣＯ２为例进行了折流元件对传质性能 实验,研究表明,折流元件可显著改善了气升式环流反应器的传热和传质性能,同时也使流动辄和明显增加。因而应根据具体反应过程并结合折流元件的选择,对气升式环流反应器进行了性能的整体优化设计。     

镁还原四氯化钛生产海绵钛过程传热分析

对镁还原四氯化钛生产海绵钛还原过程中的传热进行了数值模拟分析,提出了强化传热的方案,并对强化传热的效果进行了模拟分析.对比两者分析结果表明,通过降低反应器壁及大盖底板温度来强化传热效果明显,强化后的传热作用可以达到强化前的2倍.通过强化传热可以大幅提高还原加料速度,缩短还原生产周期,提高生产效率.     

CW原表面通道流动和传热性能的数值模拟

CW原表面通道是目前原表面回热器商业化应用最广泛的一种传热通道,其截面形状对其性能具有重要影响。文章针对原表面回热器单元流道内的流动与传热问题进行数值分析,首先,对CW原表面回热器的不同截面形状单元体建立三维数值模型并生成网格。然后在低雷诺数(Re=50~600)范围内以周期性边界条件模拟其单元内部的流动换热情况,对2种不同波纹表面形状参数的流道内的流动与换热特性进行了数值分析,结果表明,圆形与矩形截面的换热表面的平均努塞尔数Nu都随着雷诺数Re的增加而增加,但当量摩擦系数f都呈减少的趋势;两种结构中,矩形原表面的综合性能较好。     

含钒湿散料在盘式干燥机内传热传质过程分析

对盘式干燥机的干燥原理进行了分析,将含钒湿物料理想化为含湿多孔材料,在此基础上对其进行传热传质分析,将其理想化为一维扩散模型。结合盘式干燥机的结构及物料运动轨迹进行计算机模拟,获得干燥曲线。利用该程序,分析了主轴转速、进料速率、加热盘温度和物料初始湿分对物料传热传质过程的影响。     

移动床固体颗粒绕流顺排圆管的过程

工业中常用带埋管的移动床来加热或冷却固体颗粒物料,其过程涉及颗粒流与管壁间的复杂传热,而颗粒绕流圆管的流动过程对其传热效果起着决定性作用.为简化描述颗粒的流动过程,通过分析颗粒绕流圆管的特性,建立了拟漏斗流模型,并给出了模型所需颗粒绕流圆管描述参数的取值范围,模型可用以求取颗粒绕流圆管的速度场和时长等参数.建立了埋管移动床实验系统,考察了颗粒绕流顺排管束的过程;同时利用离散单元法(DEM)对该过程进行数值模拟,获得了颗粒绕流圆管的流动过程,并利用移动床实验结果对比验证了离散单元法数值模拟结果;最后,对比了基于拟漏斗流模型的计算结果和离散单元法数值模拟结果,并根据此结果对拟漏斗流模型的描述参数进行了确定.      

钢渣中游离氧化钙碳酸化反应的数值模拟

应用CFD fluent软件,以欧拉多相流模型为基础,建立流化床气固反应模型,该模型同时考虑了气固两相流动、传质和化学反应。通过UDF(User Define Function)自定义程序,实现气固两相流动、传热、传质、化学反应的耦合。研究目的为:(1) CO₂气体与钢渣中游离氧化钙反应生成碳酸钙,从而使渣的稳定性得以加强,拓展其应用领域;(2)熔渣可以作为CO₂的吸附剂,使CO₂得以固定。对直径0.24 m、高度1 m的流化床碳酸化反应器的反应过程进行数值模拟,获得了反应器内固相的体积分数、速度矢量和浓度场分布以及化学反应速率变化规律。得出最佳反应条件为:气速0.2 m/s,粒度(半径)90～150μm, CO₂:水蒸气=8:2,温度650～720℃,气体与固体颗粒充分接触的流化状态。     

氢气竖炉内气固热质传递行为的数值模拟

随着对钢铁行业绿色低碳发展要求的日益迫切,氢气竖炉已成为目前涉及氢冶金工艺的研发焦点。由于H₂还原铁氧化物为强吸热反应,氢气竖炉的供气强度主要由还原反应和加热固相炉料对应的物理能需求决定,因此造成炉内物理能与化学能的利用严重不匹配。为定量研究氢气竖炉内复杂的气固两相热质传递行为,基于双流体假设,建立氢气竖炉CFD模型,并利用其考察炉料热装技术的影响。结果表明,炉料常温入炉及所考虑工况条件下,氢气竖炉的炉顶H₂利用率仅为23.7%。由于炉料显热无法得到有效利用,热装技术难以显著改善氢气竖炉内部热状态,也就不能解决物理能与化学能利用的不匹配问题。     

Syntheses,characterization, and luminescence of two lanthanide complexes [Ln2（acetate）6（HeO）4]·4H2O （Ln=Tb（1）, Sm（2））

Two dinuclear compounds [Ln2（acetate）6（H2O）4]-4H2O （Ln=Tb（1）, Sm（2）） were obtained by the hydrothermal reaction of Ln2O3 with malonic acid at 150 ℃. Both compounds were characterized by elemental analyses, infrared spectra, and single crystal X-ray diffraction. The results showed that complexes 1 and 2 were isomorphous and crystallize in triclinic space group P 1. The coordination geometry around Ln（Ⅲ） ions in the complexes 1 and 2 was a distorted tricapped trigonal prism with a nine coordination. In the crystal, the molecular organization was further stabilized by well-defined weak hydrogen bonding interactions between the neutral dinuclear molecular units that led to the formation of a three-dimensional network. The fluorescence properties of the two complexes 1 and 2 in organic solvents were also studied. The results show that the ligand acetate favored energy transfer to the emitting energy level of Tb（Ⅲ） in complex 1. Some factors that influence the fluorescent intensity were also discussed in the article.     

Analysis and calculating for preheat temperature and average convection heat change coefficient in the continue annealing furnace

The aim of the thesis is to utilize essential theory of heat transfer,to use correlative expressions to calculate average convection heat change coefficient and heating temperature of strip in Jet Preheat Furnace （JPF）,make the calculating results accordant with production data,and make the calculation to be used the process of production.The method is to collect:entry temperature and speed of strip,temperature and speed of N₂ - H₂,to analyse heat transfer according to length and thickness of strip,jet hole and mutual position of jet piping in JPF,to analyse heat transfer and built the physical model.In mathematic model, Martin correlative expressions are tried to calculate using the data from production,and are modified in part properly.At the same time,heat boundary condition is analysed with theory of impact jet and production data.The conclusion is obtained that boundary condition is rarely average numerical value of temperature of strip and N₂ - H₂ with impact jet condition,instead of a relation of function of temperature of strip, temperature and speed of N₂- H₂,array of jet holes,diameter of hole,distance between hole and strip,and acquired a calculating expression.In calculation of examples,the thesis collected and calculated 15 kinds of strips.The thickness of strips are 2=0.51¹.41 mm,material DQ - IF、DDQ,EDDQ,SEDDQ and 340DDQ.Main assess numerical value is temperature value after strip is heated with certain speed and within section of time.Maximum error in 9 groups of numerical value in the thesis is 3.36%comparing with production data.The correlative expressions can be used in production to adjust temperature of strip through changing speed and temperature of N₂ - H₂ and speed of strip.The correlative expressions are compiled computer process.The process can be applied in on line control of production by rapid calculating speed.     

Synthesis and Fluorescence Properties of Europium,Terbium Doped Zn^2＋, Cd^2＋, and Cr^3＋ Complexes

Europium and terbium complexes with strong fluorescence intensity and long fluorescence lifetime were prepared. By replacing half of the europium or terbium ion with M （M = Zn^2＋, Cd^2＋, and Cr^3＋） using the doped method, and then incorporating it with 18-crown-6 ether and terephthalic acid, six heteronuclear samples EuZnLL＇Cl3·3H2O（1）, EuCdLL2＇Cl3·5H2O（2）, EuCrLL＇Cl4· 4H2O（3）, TbZnLL＇Cl3·4H2O（4）, TbCdLL＇2Cl3·4H2O（5）, and TbCrLL＇2Cl4 ·4H2O（6） （L = terephthalic acid, L＇= 18-Crown-6 ether） were obtained. The elemental analysis, molar conductivities, rare earth complexometry, Fourier Transform Infrared Spectroscopy （FT-IR）, ultraviolet （UV）, TGA, fluorescence intensity, and fluorescence lifetime of the samples were measured. The results showed that there were good luminescence properties for heteronuclear complexes （1）, （2）, （4）, and （5）, which were even stronger than those of the homonuclear complexes Eu2LL＇2Cl4·4H2O and Tb2LL＇2Cl4 ·4H2O, but the luminescence properties of EuCrLL＇Cl4·4H2O, TbCrLL＇Cl4·4H2O were very weak. A possible luminescence mechanism was suggested by the organic-inorganic doped mechanism and the law of intramolecular energy transfer.     

Kinetics of hydrogen absorption in alpha titanium

Hydrogen absorption and desorption often limits a material’s application. For titanium, hydrogen absorption kinetics determine its suitability for tritium storage, tritium gettering, and vacuum pump applications. This study examines the absolute rate theory energy surface which molecular hydrogen gas encounters as it is absorbed into alpha-phase titanium. This results in useful new predictions for hydrogen absorption rates, desorption rates, and surface coverages on titanium. The only energy surface which is consistent with observed activation and absorption enthalpies, while predicting all absorption/desorption rate data, is found to contain a new activation barrier. Accuracy is within a factor of 3.6 for two surface preparations and temperatures between 250 and 500 °C.     

硼的添加对Mg2Ni储氢合金吸放氢性能的影响

镁系储氢合金有着价格低廉、储氢量大等优点,作为机载储氢材料有着广泛的应用前景,但其过高的氢分解温度,过慢的分解速度等缺点制约着实际应用.采用机械球磨制备出Mg2 Ni-xB(x =0％,1％,5％,10％,15％)系列储氢合金.通过XRD分析了合金的物相结构,采用P-C-T测试仪测定了合金的吸放氢性能,研究了添加不同含量的B对Mg2Ni合金吸放氢性能的影响.研究结果表明,B的添加对合金在200和300℃下吸放氢性能的改善作用不明显,但添加B的合金在400℃下的吸氢量均较Mg2Ni高,B的添加量由1％增至15％的合金吸氢量分别为3.09％,3.00％,2.81％,2.84％,而Mg2Ni的吸氢量则只有2.60％.随着B含量的增加,含B合金吸氢量略有降低;在含B的试样中,含5％B的合金吸氢速率最大,仅需180 s便能完成吸氢.所有含B合金的放氢平台均较Mg2Ni高且较为平坦.本次实验表明,B的添加量对合金性能的提升存在一个最优值,本次实验结果显示,添加5％B相对较好地改善合金的储氢性能,提高合金吸氢量和放氢平台压的同时能保持较快的吸氢速率.     

Hydrothermal Synthesis and Crystal Structure of Lanthanum Orotate Supermolecule with A Honeycomb Structure Constructed from Mononuclear Molecules via Hydrogen Bonds

A new complex of lanthanum orotate [La（C5H3N2O4）2（OH）（H2O）6 ]·2（C5H4N2O4）·9H2O was synthesized using a hydrothermal method. The crystal structure was determined with help of single crystal X-ray diffraction analysis. The complex crystallized in orthorhombic system, Cmc2（1） space group. In the complex, the center lanthanum （Ⅲ） ion was nine-coordinated with coordination geometry of a distorted monocapped square antiprism, in which two of the nine coordinated oxygen atoms were from two orotate ligands in a monodentate mode, one oxygen atom from a hydroxyl, and the others from six coordinated water molecules. The mononuclear complex [La（C5H3N2O4）2（OH）（H2O）6 ]·2（C5H4N2O4）·9H2O was linked through the hydrogen bonds into an infinite supermolecular honeycomb structure.     

Carbon dioxide emissions reduction technology and its application prospects in the steel industry

Fossil-fuel burning greenhouse gas induced global warming has been recognized as global environmental problems,reduce and ultimately control the energy production in the use of CO₂ emissions, global energy production will be a major challenge.As a highly intensive materials and energy,iron and steel enterprises,need to be invested to produce one ton of steel about two tons of material and 0.7 t of standard coal energy,and while producing two tons of CO₂.Therefore,reducing CO₂ emissions from iron and steel industry has become the focus of the global steel industry.This paper describes an integrated domestic and international measures to control carbon dioxide emissions research progress and future technology trends, with emphasis on the domestic steel industry emissions of carbon dioxide status of technology development and industrialization of implementation of the proposed on this basis,including dry quenching technology, gas,power generation,coal moisture control technology,blast furnace injection plastics technology,the use of coking process for treating municipal waste plastics technology,sintering heat generation,low pressure saturated steam for power generation,metallurgical slag heat recovery technology,coke oven gas hydrogen technology and the other key technologies energy saving technologies,including the development,promotion and popularization of the steel industry in China will be the CO₂ emission reduction technology direction and focus.At this stage,the Chinese steel industry can be improved the energy efficiency and recycling of waste heat and energy,reduce unit GDP,CO₂ emissions;but in the long run,should increase CO₂ capture and storage on the input of technology can possible effective control of the adverse effects of CO₂ emissions.     

Gaseous hydrogen storage properties of Mg-Y-Ni-Cu alloys prepared by melt spinning

For purpose of promoting the hydrogen absorption and desorption thermodynamics and kinetics properties of Mg-Ni-based alloys, partially substituting Y and Cu for Mg and Ni respectively and melt spinning technique were applied for getting Mg_(25-x)Y_xNi_9 Cu(χ = 0-7) alloys. Their microstructures and phases were characterized with the help of X-ray diffraction and transmission electron microscopy. Their hydrogen absorbing and desorbing properties were tested by a Sievert apparatus, DSC, and TGA, which were connected with a H_2 detector. In order to estimate the dehydrogenation activation energy of alloy hydride, both Arrhenius and Kissinger methods were applied for calculation. It is found that their hydriding kinetics notably declines, however, their hydrogen desorption kinetics conspicuously improves, with spinning rate and Y content increasing. Their hydrogen desorption activation energy markedly decreases under the same constraint, and it is found that melt spinning and Y substituting Mg improve the real driving force for dehydrogenation. As for the tendency of hydrogen absorption capacity,it presents an elevation firstly and soon after a decline with the rising of spinning rate, however, it always lowers with Y content growing. With Y content and spinning rate increasing, their thermodynamic parameters(△H and △S absolute values) visibly decrease, and the starting hydrogen desorption temperatures of alloy hydrides obviously lower.     

氢气还原褐铁矿实验研究与动力学分析

本文旨在研究不同温度下氢气对褐铁矿还原度和还原速率的影响,并以此为基础分析动力学相关问题.通过热重分析深入了解褐铁矿失水状况.使用粒度为8~12 mm褐铁矿焙烧后,分别在750~950℃五个不同温度下使用4 L·min-1 H₂进行还原,并分析还原率和还原速率随时间的变化关系.研究发现:随着反应进行,试样还原率逐渐增大,五条还原率曲线在t>28 min后与还原温度排序一致.通过动力学研究计算得反应表观活化能E=15.323 kJ·mol-1,从而确定扩散为还原反应的限制环节.