基于遗传算法的20 K氦制冷机的优化设计及其热力学分析

通过计算机程序实现10 k W@20 K的大型氦制冷机的热力学过程,在此基础上分析了流程中压缩机和透平膨胀机入口压力对系统制冷系数和效率的影响。同时与Matlab编写的遗传算法接口相连交互数据,从而实现针对该制冷机热力学参数的优化。选取制冷量和系统效率的加权值为优化目标,压缩机和透平膨胀机入口压力为待优化参数,通过遗传算法(GA)的优化计算得到了稳定的最优解,表明遗传算法在优化大型制冷系统过程中可以快速高效搜索到满足目标要求的全局最优解。     

超高频脉冲管双冷指与压缩机的耦合匹配及优化

对一台压缩机分别驱动单个冷指和双冷指脉冲管制冷机进行了实验研究。实验发现双冷指脉冲管制冷机制冷性能和效率都不如单冷指脉冲管制冷机,导致性能下降的原因是由于双冷指制冷机的总阻抗与压缩机不匹配。从阻抗的角度研究双冷指制冷机与压缩机的耦合匹配特性,根据压缩机理论PV功转化效率,对与双冷指耦合的线性压缩机进行了参数优化。优化后的双冷指脉冲管制冷机可获得和单冷指脉冲管制冷机几乎一致的理论PV功转化效率。     

6W@80K气动分置式斯特林制冷机轻量化设计和性能优化

介绍了一台由中国科学院上海技术物理研究所研制的6 W@80 K气动分置式斯特林制冷机样机,主要包括压缩机的轻量化设计和整机制冷性能的优化。该制冷机包括动磁式直线压缩机和气动膨胀机,制冷机整机质量为5.5 kg。压缩机采用两个对置布置的动磁式直线电机驱动,板弹簧支撑和无摩擦的间隙密封技术。经过对直线压缩机的结构优化,在6 W@80 K的制冷性能下,压缩机的输入电功从原来的163 W降低到106 W。     

斯特林型制冷机集成制冷的发展

随着对空间制冷的要求越来越高,具有多级制冷能力的制冷机比使用多个制冷机有更高的系统效率。这种制冷机通过减小冗余提高系统的可靠性,同时又满足了空间低温系统集成化的需求。针对单个线性压缩机驱动多个膨胀机的方式,总结分析其在多温区多冷量需求下的制冷效果和发展前景。     

10W/80K高频同轴脉冲管制冷机的实验性能

介绍了一款大冷量高频单级同轴脉冲管制冷机的基本结构、数值模拟和实验性能。其线性压缩机采用Redlich动磁式直线电机驱动,压缩活塞对置布置,使用板弹簧支撑和间隙密封技术,80 K温区工作时的电机效率在83%以上。膨胀机的蓄冷器和脉冲管为同轴型布置,这种结构使冷头与器件之间的耦合非常方便。使用数值软件对制冷机整机和调相部件进行数值模拟,并对模拟结果进行实验验证。对制冷机的运行频率和制冷性能进行实验研究,制冷机在210.3 W输入电功时能获得10 W/80 K的制冷性能,比卡诺效率为12.66%,运行频率为62 Hz,整机重量小于5.5 kg。     

一种气动弹簧内置结构的斯特林制冷机设计

设计了一台100 W/77 K的分置式大冷量斯特林制冷机,其中气动弹簧组内置于空心排出器中,缩小了膨胀机的轴向尺寸。热端膨胀腔与压缩腔之间通过辐射状分布的分离式"明渠"结构通气槽连通,降低了加工难度。压缩机为对置式双气浮活塞结构,最大输入功率2 kW。介绍了该制冷机的热力设计和动力设计,给出了参数设计结果,最后分析了压缩机各类损失对制冷效率的影响。模拟结果表明,在1 064 W的PV功下,制冷机77 K可以获得104 W制冷量,当压缩机效率大于85%,热端温度20℃时,电功消耗小于1 252 W,比卡诺效率大于23%。     

单阀膨胀机的进气阀结构

在中小型氦液化装置和氦制冷机中,活塞膨胀机效率比透平膨胀机效率高,它设计简单,容易控制,操作方便,能适应高的压比,因而具有很重要的地位。由于氦低温技术的迅速发展,对氦制冷装置操作的可靠性提出了严格的要求。可以在某种意义上说,目前所普遍采用的克劳特制冷循环,膨胀机运转的可靠性从根本上决定了氦制冷装置操作的可靠性。     

逆布雷顿循环空气制冷机的性能分析

针对开式逆布雷顿循环空气制冷机的热力性能展开理论分析,建立压缩机、膨胀机和回热器3大部件的制冷机系统模型.就部件性能和流程选择、环境温度、制冷温度等系统参数以及压比等设计参数对空气制冷机性能和COP值的影响进行了研究,证明存在着一个最佳的压力比πopt～4使制冷系统的制冷系数最大.提出了进一步提高制冷机效率的改进方案,对系统参数和设计参数进行了优化设计.     

苏联低温工程和低温制冷机的发展（续）

克劳特循环制冷系统中广泛使用活塞膨胀机和透平膨胀机，这是因为它们能提供非常有效的制冷过程。斯特林机也是一种有效的制冷机，在苏联普遍采用这种制冷机。这里我们将分别介绍一些在苏联使用的有关膨胀机和斯特林机的研究工作，以及一些产品型号。     

不可逆恒温热源空气制冷机的炯经济性能优化

文章用有限时间热力学理论和方法,研究了恒温热源条件下不可逆空气制冷机的有限时间炯经济性能,导出了利润率解析式。用数值计算分析了压比、热源温比、热导率分配、压缩机和膨胀机的效率等参数对利润率的影响,并优化了循环压比和换热器的热导率分配。通过价格比,将有限时间炯经济性能目标与制冷率、熵产率及生态学目标建立了联系。所得结果对实际空气制冷设备的设计有一定指导意义。     

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 ...