HOT器件用自由活塞斯特林制冷机研究进展

自由活塞斯特林制冷机可用于红外探测器组件的冷却,具有振动小、寿命长等优点。随着红外探测器工作温度的提高(HOT器件),斯特林制冷机进入更小尺寸、更低质量、更高性能、更低功耗和更低成本的发展方向,即超小型斯特林制冷机。文章总结了近10年国内外超小型自由活塞斯特林制冷机的发展概况,并对超小型自由活塞斯特林制冷机的设计理念进行了介绍。     

红外探测器与小型制冷机

小型致冷机可以用来冷却红外探测系统的敏感元件。工作范围为60K到80K。制冷量为0.1瓦到2瓦。这两个指标又取决于冷却的探测器数目和探测器一制冷机接合面的热效率。这类小型制冷机的平均无故障时间应当大于2500小时,而且温度回升要很小。根据菲利浦公司几十年来从事低温工作的经验,在空间红外探测器上,采用斯特林循环的小型制冷机可以     

空间用3 W@80 K脉冲管制冷机实验研究

为冷却某空间用红外探测器,研制了一台斯特林型脉冲管制冷机。该制冷机为单级同轴型结构,整机重量4.5 kg,设计寿命5年。系统介绍了脉冲管制冷机系统结构及实验装置,测试了制冷机性能及其与杜瓦耦合后的降温特性曲线,实验结果表明,脉冲管制冷机在80 K可提供0—3 W制冷量,比卡诺效率11%,其制冷量可充分满足杜瓦组件的低温和长寿命的工程需求。     

大面阵探测器与斯特林制冷机热耦合结构仿真设计与实验

随着空间红外探测器向大面阵和长线阵列方向发展,探测器的低温平台难以被制冷机直接冷却,传统的单点热耦合方式也无法满足低温阵列的温度均匀性要求.提出一种新型的大面阵探测器与斯特林制冷机之间的桥板式热耦合结构,利用Workbench软件对耦合结构的温度分布进行了仿真分析,并进行实验验证.结果表明:冷平台的温度均匀性达到0.2...     

大面阵红外探测器冷平台仿真设计与试验

随着线列红外探测器面阵规模越来越大,传统的制冷机与红外探测器单点连接的耦合方式已经无法满足红外探测器芯片温度均匀性的要求.本文对某型号大面阵红外探测器冷平台及其辅助支撑、柔性冷链进行了相关的结构设计、仿真分析与试验验证,设计的冷平台在正弦和随机振动时变形量小,温度均匀性不大于0.919 K,可以满足大面阵红外探测器的工...     

制冷机在空间红外遥感领域的应用研究

空间红外遥感探测器主要采用机械制冷机冷却到工作温度,以获得最佳探测效果。通过对国内外红外遥感探测器用制冷机的研究,分析了机械制冷机的发展方向,即大冷量和深低温的制冷机;讨论了制冷机的两个主要性能评价方法,寿命评价和微振动评价;总结了制冷机电磁兼容性、制冷机探测器耦合设计方面取得的经验和需要开展的工作。     

斯特林型脉冲管制冷机的最新进展

介绍了斯特林型脉冲管制冷机在理论分析和实用化方面的进展。与斯特林制冷机相比 ,由于低温端没有运动部件 ,脉冲管制冷机在寿命、可靠性和振动等方面有明显的优势 ,同时直流现象的发现和对它的抑制 ,以及双向进气、长颈管等调相机构的应用 ,使得斯特林型脉冲管制冷机的效率也可以达到或超过斯特林制冷机 ,从而使斯特林型脉冲管制冷机在空间、红外器件和超导器件冷却等方面有广泛的应用     

制冷机直接冷却超导二元电流引线的优化

二元电流引线是制冷机直接冷却低温超导磁体系统的关键技术之一,对制冷机直接冷却的二元电流引线的传热情况进行理论建模和数值计算,确定制冷机的最小功耗和热力量优的热截流温度点工况,并对影响制冷机最小功耗的各种因素进行讨论。     

有阀型小孔脉管制冷机的深入研究

为了克服第三代脉管制冷机存在的制冷温度不稳定的缺陷,本文从提高脉管制冷效率,进一步降低制冷温度的角度,对有阀型小孔脉管制冷机进行了研究。通过理论计算和实验改进,有阀型单级脉管制冷机取得了３４Ｋ的无负荷制冷温度,在８０Ｋ获得３０Ｗ以上的制冷功率,其制冷效率达到国外同类商品型有阀脉管制冷机的水平。     

测定保温材料导热系数的自补偿圆管法的方法误差分析

本文对测定保温材料导热系数的自补偿圆管法的方法误差进行了分析。在００４～０１０Ｗ／（ｍ·Ｋ）导热系数范围内，固定功率补偿子方案的方法误差不超过２３％；而在００４～００６和００６～０１０Ｗ／（ｍ·Ｋ）分区域范围内则分别不超过１３％和１０％。这表明，测定保温材料导热系数的自补偿圆管法采用固定补偿因子方案在原理上是可行的。     

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.     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...