一种新型多温区恒温箱均温性的数值模拟与实验验证

本文针对自行设计的一种新型的具有三个箱体的多温区恒温箱进行其均温性的研究。以多温区恒温箱的一个箱体为研究对象,建立了三维稳态数值模型,模拟了加热器情况不同时该箱体内的温度分布。结果表明,采用方形薄片加热器并布置于风机下方时,该箱体内的温度场最均匀。恒温箱三个箱体的加热器均采用上述情况后,对其设定了工况1(各箱体的设定温度分别为-15℃,-10℃,-5℃)和工况2(各箱体的设定温度分别为-20℃,-15℃,-10℃)进行实验。结果显示,工况1(即模拟工况)下的模拟值与实测值较吻合,最大误差为3.1%;两种工况下各箱体的温度均匀度最大为0.54℃。结果表明,在不同的测试工况下该多温区恒温箱各箱体内的温度分布都能维持均匀。     

基于Fluent的多温区保温包装箱温度场仿真分析

目的探究多温区保温包装箱在不同条件下保温箱内部温度场及保温效果的影响。方法以冷藏区(0~8℃)、冷冻区(0℃以下)双温区EPP保温箱为研究对象,采用Ansys Fluent工具建立等比模型,通过实测实验保温时间来验证模型的可靠性。选取蓄冷剂摆放位置、箱体材料、外界环境温度等3个因素,分别进行仿真计算分析其对保温箱内部温度的影响。结果通过仿真模拟得出蓄冷剂侧面摆放时内部空气温度场最为均匀,保温效果最好,保温时间相较于最差的边缘摆放冷藏区提高了41.37%,冷冻区提高了51.59%;3种箱体材料中EPU材料的保温箱保温效果最好,保温时间相较于EPP材料,冷藏区提高了36.84%,冷冻区提高了41.24%;随着外界温度由23℃升高到40℃,箱体保温效果冷藏区降低了59.73%,冷冻区降低了55.04%。结论通过计算机仿真方法可对多温区保温箱温度场进行数值模拟,其结果可为多温区箱体实现多温共配提供一定的理论依据。     

流通环境对液氮充注蓄冷配送箱保温性能的影响

目的 为了提高液氮充注蓄冷配送箱在流通过程中的保温性能,保证配送品质。方法 搭建配送箱流通环境模拟试验平台,研究不同外界风速、外界温度和振动频率对蓄冷配送箱内空气温度变化和温度场分布的影响。结果 试验结果表明,当外界风速增大时,箱体内部环境的升温速度也会增大;外界温度对液氮充注完毕后箱内最低温度产生较大影响,箱体内部空气最低温度随外界温度降低而降低,同时始终在运输过程中维持较低的温度,箱体内温度场均匀性先提高后降低;振动对箱体内部环境的升温速度影响较大,而随着振动频率增大,箱体内部的温度场均匀性变差。结论 该研究可为蓄冷运输配送设备的设计与优化提供参考。     

环形热管蓄冷保温箱的模拟优化与实验研究

目的 解决蓄冷冷链运输中存在的温度波动大、均匀性差等问题。方法 文中提出通过环形热管来优化箱内温度场均匀性的方案，以柠檬为实验材料，采用FLUENT数值模拟软件对不同环形热管结构下柠檬保温过程进行仿真，并对4层环形热管模型进行实验验证，确定箱内温度分布规律。结果 环形热管均对保温箱温度场均匀性有明显改善作用，4层环形热管与无环形热管的蓄冷保温箱相比，蓄冷保温过程结束时，不均匀度由1.71减少为0.83，降低幅度为51.46%，温度极差可由8.32 ℃减小为3.24 ℃，降低幅度为61.06%。顶部留出的空隙会出现环流现象，能一定幅度地减少有效蓄冷保温时间，增大温度极差和温度不均匀度。结论 验证实验和模拟结果的温度偏差在1.25 ℃以内，说明建立的模型适用于该蓄冷保温箱的数值模拟。针对文中箱体结构，最佳热管环数为4层左右;其结果可为优化蓄冷保温箱的温度分布提供参考依据。     

采用系统仿真方法数值模拟双层风幕立式陈列柜

将制冷系统的仿真模型与立式陈列柜的热卷吸系数关联式模型结合,提出双层风幕立式陈列柜系统的系统仿真方法,并编制计算机程序进行了仿真实验。根据仿真实验的结果分析了陈列柜系统冷凝温度、蒸发器面积和柜体参数的变化对陈列柜风幕送回风温度变化的影响规律。仿真实验的结果和试验测试值进行了对比分析,其最大偏差为1.9℃,平均偏差为0.9℃,说明本仿真算法具有工程应用价值。     

真空系统内一种加热器温度场分布有限元分析

为了提高真空系统内一种加热器的温度场分布均匀性,利用有限元分析方法,借助ANSYS Workbench仿真温度场,通过对单圈钨丝结构外加圆倒角釜结构上的改进,确定了获取均匀的温度场的方法。在电阻丝加热功率为45 W,对直径50.8 mm的蓝宝石晶元加热温度均达到200℃的情况下,分别对两种加热器进行了仿真分析。结果表明:单圈钨丝结构外加圆倒角釜的加热器对晶元加热的温度场均匀性较差,温度差异为41.13℃。多圈钨丝螺旋结构外加抛物面釜对晶元加热的温度场均匀性较好,温度差异仅为2.30℃,可作为真空系统内一种理想的高均匀性加热器结构。对GaN阴极均匀性的检测表明:通过改进加热器结构,使得制作的GaN光阴极发射不均匀性由原来的28%改善为小于10%。研究成果为真空系统内部加热器的优化改进提供技术支撑。     

不同送、回风口位置对办公室温度场分布的影响

为改善办公室夏季"外墙侧热、内墙侧冷"的现象,以珠海某办公室为研究对象,利用Airpark软件对该办公室现有风口布置及改进风口布置进行气流组织仿真模拟,分析了不同送、回风口位置下的室内温度场分布,发现合理的送、回风位置能够使室内温度均匀,改进后室内最大温差由5℃降低到1.5℃,提高了人体舒适性。     

内藏直吹式空调室内机数值模拟及气流组织评价

对天花板内藏直吹式空调器测试房间为模型,应用AirPak软件在制冷运行时不同送风参数下的流场和温度场进行了数值模拟。并以温度不均匀系数、速度不均匀系数和能量利用系数作为气流组织评价指标。结果表明:相同风量下,送风角度越小,室内温度和速度越均匀,能量利用越好;相同送风角度下,风量越大,室内温度和速度越均匀,能量利用越好。     

冰箱内温度场与流场数值模拟

冰箱箱体内温度场和流场分布对食品的保存质量有很大的影响。为了得到箱体内温度场和流场的实际分布及其影响因素,作者搭建了电冰箱箱体测试实验台。用Agilent34970A数据采集／开关单元等组成的温度测试平台对冰箱箱体各内壁面和六个空间特定点的温度值进行监测。建立了三维稳态数值计算模型,运用FLUENT软件对箱体内的流动和换热进行了数值模拟。通过将六个空间特定点的模拟结果与实验结果进行对比,两者吻合较好,从而验证了计算模型的准确性。     

基于不同大气压力下多种翅片型式换热器的换热特性仿真模拟研究

大气压力的不同,将对换热器的换热性能带来一定的影响,而不同翅片型式的换热器处在同一种大气压力下,对各自换热性能影响的程度如何,因此有必要对其进行研究。在GAMBIT中建立平板式、均匀倾角波纹式、前平板-后均匀倾角波纹式的换热器的物理模型,设置在大气压力100k Pa、90k Pa、80k Pa、70k Pa、60k Pa、50k Pa的工况下,通过FLUENT6.3对所建的模型进行仿真模拟计算,然后通过观察所建物理模型的中心侧面的温度云图,分析中心侧面和翅片出口处的加权平均温度来研究这三种翅片型式的换热器处于同一种大气压下的换热能力,并以10k Pa为间隔,来研究压力变化对三种翅片型式的换热器换热能力影响的程度。模拟结果为:在同一压力下,均匀倾角波纹式换热器的换热能力在三者中最大,前平板-后均匀倾角波纹式的换热器的换热能力次之,平板式的换热能力最小;压力下降对均匀倾角波纹式换热器的换热能力影响最小,前平板-后均匀倾角波纹式的换热器的换热能力影响次之,平板式的换热能力影响最大。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.