高真空多层绝热低温容器完全真空丧失后升压规律的试验研究

高真空多层绝热低温容器是一种危险性很高的压力容器。绝热夹层完全的真空丧失是可能发生在高真空多层绝热低温容器上的、并会对低温容器带来严重的安全隐患。在搭建了高真空多层绝热低温真空丧失试验台的基础上,用试验的方法研究了低温容器的绝热材料层数和初始充满率对其真空丧失后无排放贮存过程中升压的影响。试验结果表明,高真空多层绝热低温容器绝热夹层内的绝热材料层数及其初始充满率都对容器完全真空丧失后的升压过程有着重要影响。     

高真空多层绝热低温容器真空丧失试验研究

通过高真空多层绝热容器真空丧失试验，分析了不同绝热结构下容器真空丧失后的升压规律，同时讨论了容器内气液状态变化。利用试验数据计算了容器真空丧失后的热负荷变化，并综合比较分析了不同绝热结构下的漏热量、气体升压、液体温度变化。经研究发现，容器夹层真空丧失后气液相处于不平衡态，气相空间压力变化呈现出三种不同状态，夹层的漏热量决定了液体升温和容器升压速度。     

深冷真空绝热容器标准技术发展与展望

深冷真空绝热容器包括固定式深冷容器和移动式深冷容器二大类,结构型式多种多样,深冷容器的规范设计和制造,以及安全运行,需要多项关键技术,包括结构设计技术、低温绝热技术和标准化技术.深冷真空绝热容器的标准化技术发展可为我国低温储运行业快速规范发展起到一定的促进作用.     

高真空多层绝热超低温容器漏热分析

为解决高真空多层绝热超低温容器漏热的设计难点,通过对高真空多层绝热超低温容器支撑结构、容器接管、残余气体传热、辐射传热进行漏热分析,介绍了理论计算和数值模拟计算过程,同时提出了以机械构件和多层绝热结构优化为主的降低漏热的措施,最后将超低温容器蒸发率转化为允许漏热量,并以此作为性能考核指标,建立高真空多层绝热超低温容器漏热设计流程图,分析结果可为工程中的漏热设计提供参考。     

静态升压法在真空粉末绝热低温液体贮槽检漏中的应用分析

真空粉末绝热低温液体贮槽是用于液氧、液氮、液氩等低温液体贮存的一种大型容器,广泛用于化工、冶金、玻璃制造等行业,由于其绝热方式为真空环境下的粉末（一般为珠光砂）绝热,因此决定了检漏在这类贮槽制造过程中是一个必不可少的重要环节。检漏方法有很多,如氦质谱...     

高柔性真空多层绝热软管的研制

通过改进优化真空多层绝热软管外软管、内软管、支撑、法兰热桥及绝热层的结构研制出一种高柔性真空多层绝热软管,兼顾了管道的柔性和绝热性能,使得真空软管的结构更加紧凑。     

低温液体运输车轻量化设计的研究

介绍了低温液体运输车轻量化设计的主要方法，在保温结构上用高真空多层绝热取代传统的珠光砂粉末绝热，在工作方式上，用低温泵排放取代自增压转注，在结构上运用有限元等优化设计方法。文章对国内外同类产品在技术参数上进行了比较。     

真空多层绝热管道氮气置换技术的研究

真空多层绝热管道漏放气速率是考核管道绝热性能的重要指标,在生产过程中,影响其漏放的因素有抽空机组本身的泄漏情况、加热温度、加热时间、氮气置换、抽空周期等.到目前为止,真空多层绝热管道的生产工艺没有明确的标准及规范,为得到较为优化的生产工艺,论文介绍了其中一个重要的因素-氮气置换技术,对其进行了理论与试验分析,研究了氮气置换的注氮温度、注氮时间、注氮次数对真空多层绝热管道的影响,通过理论与实践总结出氮气置换相关参数的优化值,为进一步工艺理论规范化提供借鉴.     

固定式真空绝热低温容器的支撑结构

介绍了几种应用在固定式真空绝热低温容器中的支撑结构以及降低支撑构件漏热的方法和构件选材的原则,并针对立式和卧式容器各种支撑形式的结构特点、绝热性能、受力特点,以图例的形式逐一介绍。     

真空多层绝热管道技术现状

论文综述了真空多层绝热管道发展过程和现状,阐明了其具有绝热性能好、重量轻、损失小等优点,是航天试车台和发射场长距离低温输送管道的最佳选择,介绍了目前常用的三种连接方式的性能和阐述了其各自应用特点,重点介绍了采用CO_2冷凝真空技术,展望了真空多层绝热管道的发展方向。     

Development of variable temperature instrument for sensor calibration

An experiment to calibrate temperature sensors at cryogenic temperature has been performed. The main objective of this study was to develop a precise instrument for calibrating the temperature sensors over a temperature range of 4 K to approximately room temperature without liquid helium. The instrument consists of radiation shields, a sensor block, an electric heater, a cryocooler and a vacuum chamber. In a vacuum chamber, the cold head of the cryocooler is thermally anchored to the sensor block to bring the apparatus to a desired temperature. An electric heater is placed at the second stage of the cryocooler to control the temperature of the sensor block. The entire apparatus is covered by radiation shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. The dimensions of components including instrumental wires are optimized to reduce total heat invasion from room temperature into cryogenic temperature. The vacuum chamber is pumped down and cooled to cryogenic temperature by a cryocooler. The resistance of each temperature sensor is measured at steady state as well as cooling down and warming up cycles, and the performance of calibration is discussed with respect to the sensitivity and resolution.     

A simple pneumatic device for plunge-freezing cells grown on electron microscopy grids

A detailed design for a simple and inexpensive variable-speed (1.0–5.8 m s^?1) pneumatic plunge-freezing device is presented. Cultured cells, grown on Formvar-coated 75-mesh gold finder grids, are pneumatically driven into a stirring mixture of propane/isopentane (3:1) cooled by liquid nitrogen (LN₂). Premature freezing of the sample in the cryogenic vapors above the cryogen is prevented by plunging through an entry tube into an insulating box, to which a partial vacuum is applied. The cryogenic vapors are drafted into the box at the level of the liquid cryogen by the vacuum, thereby preventing a layer of cold gas from collecting above the cryogen. To prevent the sample from thawing during transfer from the cryogen to the substitution medium, the box top is removed and compressed air is forced through a corrugated tube running the length of the box. The resulting boiling LN₂ creates an atmosphere below ?120°C in which the transfer can be accomplished.     

Investigation of heat transfer in an oil cooled piston with and without ceramic insulation on crown face

A numerical method is presented for calculating the temperature fields in a semi-adiabatic diesel engine piston having a cooling oil canal. The crown face of the piston is coated by a 2 mm thick oxide based ceramic insulating material. The non-ideal thermal contacts between the piston circumference and cylinder wall are also considered. A detailed analysis has been given for estimating the boundary conditions of the cylinder-piston assembly of an internal combustion engine. The isothermic distribution in the piston body and the heat flow rate through the different cooling media at four different engine loads have been depicted both for the cases with and without insulation coating. The results indicate a reduction (12–30%) in heat loss through the piston by use of an insulation coating at the piston crown face, assuming that both the heat transfer process from and the temperature of the combustion products remain unchanged.     

离心式液氢泵的动力特性与传热特性分析

对输运液氢的离心式液氢泵进行低温结构设计与动力单元分析,叶轮是速度能转变为压力能获得高压流体的重要部件,对离心泵的稳定输出特性有较大的影响。其中,转子(包括转轴和叶轮)是连动部件,也属于低温泵结构性传热部件。对应用于储运系统的某小流量高压头的离心式液氢泵的叶轮和转轴部件,进行功能分区,利用CFD内嵌模块对其进行数值计算。根据运行系统中输送载荷,对低温条件下的转子部件进行热-结构耦合瞬态应力应变分析,获得其动力特性;采用流固耦合方法,对叶轮区的流体域进行数值计算,分析不同流体载荷下叶轮表面应力分布;对低温离心泵轴-叶轮的传热区进行设计,分析低温-室温隔热效果,为离心式液氢泵的设计研发、结构优化和性能改进提供理论依据和参考。     

小功率真空贮能式即热热水器的研究

文中主要介绍了小功率真空贮能式即热热水器的主要结构、研究机理及技术特点。这种热水器只需1kW以内的小功率电热元件,结合真空保温技术即可达到即热的目的,充分体现节能的优势。     

Cryogenic apparatus for study of near-field heat transfer

For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10(0) to 10(3) μm. The heat transferred from the hot (10 - 100 K) to the cold sample (～5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within ～2 nW∕cm(2) and ～30 μW∕cm(2) is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.     

一种高灵敏度超导接收前端的结构设计与仿真

空间用超导接收前端必须经受热真空和振动、冲击等环境适应性测试的考验,需要可靠的集成设计来控制制冷机冷指的变形量,而可靠的结构设计是关键。文中介绍了一种空间用高灵敏度超导接收前端的小型化、低漏热和高可靠性的结构设计方案。该接收前端采用自制的分置式斯特林制冷机(2.8 W@77 K)。采用特殊结构设计的铝板底座有效地将制冷机产生的热量传送到安装平台,满足了热真空指标。采用冷焊制成的异种形状的柔性导热带大大减小了制冷机冷指受应力冲击所造成的变形。采用隔热支撑结构连接超导滤波器和低温放大器等器件,既满足了机械强度要求,又有效地减小了漏热。对关键部件进行了实物测试,并采用Pro/E和ANSYS对整机进行仿真,验证了这种结构设计的可行性。     

低温绝热气瓶绝热性能检测时间优化分析

蒸发率是用来检测低温绝热气瓶绝热性能是否合格的一个重要指标,但是目前仍存在检测时间较长的不足。依据一维传热模型,提出了一种基于一定检测时长的优化检测方法。该方法以少于24 h的实际检测数据作为样本来获取传热系数等部分参数,并利用获取的参数预测剩余时间的蒸发流量,最终实现缩短检测时间的目的。为了验证优化方法的有效性,搭建了恒温箱实验台并进行了相关试验测试。对比结果表明,计算结果与试验值符合良好,误差在5%以内,验证了模型的可靠性与实用性。