氩气微槽道焦-汤效应制冷器实验研究

汉普逊型J-T效应制冷器结构不紧凑,其支撑芯轴占据较大空间,换热效率低。为提高其换热性能,将换热效率高的微槽道技术应用于J-T效应制冷器,设计出一种新型的多层微槽道J-T效应制冷器试件,并搭建实验台对其进行性能测试与分析。实验以进口温度7.5℃和10.5℃,进口压力4 MPa至8 MPa的氩气为冷源,对各测点的温度进行采集,并完成冷端温度的性能测试与分析。实验表明,在相同的进气温度下,随着进气压力增高,冷端温度降低,在进气温度为10.5℃、压力为8MPa时冷端温度最低可达-41.1℃。同时,在相同的进气压力下,冷端温度随进气温度的降低而降低,在进气压力7 MPa下,进口温度7.5℃比10.5℃的冷端温度低6.1℃。     

全金属芯片型节流制冷器的实验研究

采用不锈钢为材料以金属蚀刻芯片和真空扩散焊接工艺制成了芯片型节流制冷器,搭建了微型节流制冷器系统,以高压氮气和氩气为工质,研究了不同入口压力下无负荷节流的制冷温度和流量特性。实验结果表明:采用氮气为工质时,在入口压力为10.5 MPa工况下,最低制冷温度为102.9 K;采用氩气为工质时,在压力为8.6 MPa工况下可获得112.0 K的最低制冷温度,降温速度也有效提升。在大流量下,低压通道阻力增大将导致节流后背压和蒸发温度提高,采用氮气和氩气作为工质在压力分别高于10.5 MPa和8.6 MPa时,制冷温度开始回升。验证了基于金属微通道蚀刻工艺技术的芯片型节流制冷器可行性,表明采用金属微流道芯片可以大幅提高耐压能力、机械强度和降温速率。     

基于半导体制冷预冷的氮气冷冻刀系统实验研究

设计了基于三级半导体制冷的氮气J-T效应预冷器,研制了直径3 mm的冷冻探针,搭建了基于半导体制冷预冷的氮气冷冻刀降温实验系统。实验结果表明,本系统中冷冻刀在氮气初始压力8.5 MPa下节流温度可达-98.3℃,在初始压力为12 MPa下,节流后的氮气最低温度可达-120℃;冷冻刀的冷量随刀头恒定制冷温度的不同而不同,在氮气初始压力为8.5 MPa下,其制冷温度恒定为-47℃时,冷量为30 W,可满足杀死细胞的要求;水中冻结实验表明,氮气初始压力越大,冷冻刀冷量越大。     

微小型焦-汤效应节流制冷器发展与研究

本文综述了微小型焦耳-汤姆逊(J-T)效应节流制冷器近年来的发展情况,从制冷器的结构型式演变以及理论研究两方面对现有技术和研究成果进行了总结,在分析有关文献的基础上对微小型J-T效应节流制冷器的发展方向做了进一步的展望。随着应用领域的拓展及加工工艺的进步,制冷器的结构型式越来越趋于小型化、多样化,借助微刻蚀技术制作的多级、多层、多通道微小型J-T节流效应制冷器具有很大的发展空间;在理论研究方面,由于微小型J-T节流制冷器的运行机理较复杂,目前的理论模型多是基于不同程度的假设,因此,对于微小型J-T效应节流制冷器的理论研究,不仅需建立并求解更切实际的理论模型,还需关注与及时应用相关的基础研究成果。     

氩气J-T低温制冷器稳态特性仿真研究

在VB平台上用有限差分法,对一种具有螺旋翅片管式回热装置的氩气J-T低温制冷器进行了稳态仿真模拟.充分考虑流道的几何形状和流体流动状态,提出了合理的数学模型;应用氩气物性数据库及VB计算程序分析了进气温度、进气压力及环境温度对J-T低温制冷器性能的影响,界面友好,结果表现直观,并通过引用相类似结构的实验数据验证仿真模拟...     

微型节流制冷器氮气氩气超高压供气系统设计

节流制冷器的工作性能与节流工质有很大关系.设计了一套超高压的氮气和氩气供气系统,其目的是提供超过100 MPa超高压的氮气和氩气气源,并满足常规的高压气源需求,同时提供了功能先进的气体纯度在线检测、超高压力在线检测和计算机控制功能,并有单独的模块单元,可以对氮气和氩气进行适合比例的混合,或提供其它成分的节流制冷器的混合工质气体.设计有不同气瓶容积下节流制冷器的跑合实验单元,对节流制冷器的耗气性能进行测试.     

真空高压气淬炉中淬火气体压力、流速和类型对工件冷却性能影响的数值模拟

本文运用FLUENT软件,通过大量的计算机模拟,研究了真空高压气淬炉中淬火气体压力、进口速度、气体类型对工件冷却性能的影响.通过对比氮气在0.45 MPa、0.6 MPa、1.0 MPa和1.5 MPa淬火压力下工件的冷却速度,量化了淬火压力对工件冷却速度的影响程度.氮气在0.6 MPa下,将气体速度由40 m/s增至60m/s,工件冷却速度提高27％,但风机功率增加3.4倍.由于气体体积流量一定的情况下,淬火气体比热和密度的协同影响了换热系数的大小,通过计算机模拟了四种淬火气体氢气、氦气、氮气和氩气对工件冷却速度的影响,得出在相同气体压力和流量下,四种气体的冷却能力是:氮气＞氢气＞氦气＞氩气;在消耗相同的风机功率下,密度小比热大的气体冷却能力高,四种气体的冷却能力依次是氢气＞氦气＞氮气＞氩气.     

冷冻消融探针J-T节流制冷器降温特性的实验研究

通过实验测定了不同氮气预冷温度、热负荷条件下冷冻消融探针内J-T节流制冷器温度与流量。实验结果表明:冷冻消融探针工作温度随氮气预冷温度变化而变化,热负荷越大所需氮气预冷温度越低;氮气预冷温度过低会造成制冷量浪费与回热换热器换热效率降低;氮气流量随高压氮气出口温度的降低而增大,除临界区域外氮气计算流量符合测试结果。     

冷冻消融探针J-T节流制冷器降温特性的实验研究

通过实验测定了不同氮气预冷温度、热负荷条件下冷冻消融探针内J-T节流制冷器温度与流量.实验结果表明:冷冻消融探针工作温度随氮气预冷温度变化而变化,热负荷越大所需氮气预冷温度越低;氮气预冷温度过低会造成制冷量浪费与回热换热器换热效率降低;氮气流量随高压氮气出口温度的降低而增大,除临界区域外氮气计算流量符合测试结果.     

热电冷却微流体芯片的温度响应特性优化研究

精确的温度调控是微流体技术在生化分析和医学诊断等方面发展应用的重要保障。为实现微流体芯片目标区域的温度控制，本文设计了基于异型结构热电制冷器的微流体芯片温度控制系统，通过数值模拟和实验测试分析了该温控系统的传热特性及及温度响应特性。研究结果表明：采用的热电制冷器可将微流体芯片样品池的温度降至-24 ℃，但样品池的降温速率远小于热电制冷器的冷端降温速率，存在温度响应迟滞问题。为此，进一步提出了带有聚冷结构的系统优化，结果表明：聚冷结构的引入虽然会带来少量的冷量损失，但可以显著提升该温控系统的温度响应速率，有效减少响应时间。对于T型聚冷结构，当下底直径为14 mm和10 mm时，可分别将温度响应时间减少30%和40.7%。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

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.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

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.