大型低温液体贮存站贮罐设计选型论证(续)

运用热力学第一定律对低温液体在贮存、运输转注过程中的热力学特性进行了分析,定量分析、计算了低温液体节流过程的节流汽化率值,提出了减少节流过程所形成的汽化率的有效途径;论证了在大型低温液体贮存站贮罐设计选型时,应根据不同的低温液体液源、液体品质和操作工况等条件进行设计选型;论证了除合理地选择正确的低温液体贮罐结构形式外,还应高度重视低温液体贮罐的安全泄放设计,以确保低温液体贮存站的安全性能、使用性能和技术经济性能均处于最佳状态。     

车用LNG气瓶副安全阀泄放口设置的思考

车用LNG气瓶安全阀是气瓶在异常状态下超压泄放装置,对车用LNG气瓶安全使用起到了重要的保护作用。该文通过标准分析和超压瞬时能量计算,对市场流通的2类车用LNG气瓶副安全阀泄放口的设置进行思考和讨论,分析得出这2类产品副安全阀泄放口的设备不符合标准要求,同时副安全超压泄放时会导致橡胶塞弹射,存在安全隐患,最后提出副安全阀泄放口的3种结构优化思路,为更安全、更规范的车用LNG气瓶副安全阀泄放口的设置提供借鉴和支持。     

蒸汽安全阀的选择计算及其管道设计的注意事项

随着《中华人民共和国特种设备安全法》的公布并施行,加强特种设备安全工作,预防特种设备事故,已上升到国家法律层面。作为锅炉、压力容器、压力管道等特种设备的安全泄放装置,安全阀的选型与设置尤为重要。本文仅对蒸汽安全阀的选择计算及其管道设计中的几个重要问题进行了详细的探讨,并提出了蒸汽安全阀管道设计参数的确定方法,以便其能够更有效地发挥安全泄放作用。     

蒸汽安全阀的选择计算及其管道设计的注意事项

随着《中华人民共和国特种设备安全法》的公布并施行,加强特种设备安全工作,预防特种设备事故,已上升到国家法律层面。作为锅炉、压力容器、压力管道等特种设备的安全泄放装置,安全阀的选型与设置尤为重要。本文仅对蒸汽安全阀的选择计算及其管道设计中的几个重要问题进行了详细的探讨,并提出了蒸汽安全阀管道设计参数的确定方法,以便其能够更有效地发挥安全泄放作用。     

某液氯储罐爆破片选型计算

爆破片是压力容器中重要的安全泄放装置,文章首先介绍了爆破片的原理及结构分类,在此基础上选取检验工作中常见的液氯储罐,计算了在火灾工况下其安全泄放量及使用爆破片时的最小泄放面积,并且简要介绍了爆破片与安全阀联合使用的相关内容.     

大型低温液体贮罐设计制造

介绍了大型低温液体贮罐的结构特点,以及结构尺寸、内罐、外罐、保温和基础等设计要点,阐述了大型低温液体贮罐抗震设计、施工安装、清洗和试验等有关问题。     

低温绝热储运容器的储运低压安全泄放设计

根据低温绝热储运容器在使用过程中存在的经济性和安全性问题，通过讨论密闭容器内低温液体气液两相的温度、压力、密度的平衡关系，提高了设定储运压力和相应的低压安全泄放装置的设计方案，使低温绝热储运容器的设计更趋合理。     

低温流体安全处理现行规范澳大利亚标准 AS 1894-1976

本规范叙述了低温液体或气体在使用中可能出现的各种危险、预防措施、贮罐和辅助设备使用时的注意事项、操作程序,以及氧气、液化空气、氮、氩、氖、氪、氦、氢、液化天然气的有关安全事项。并附录了各种事故过程的处理、医疗处理、距大型液氧贮罐的最小间距等。为配合贯彻国际标准或国外先进标准,下面译载澳大利亚1976年颁布的一个现行规范。该规范是参考英国低温学会1970年出版的《低温安全手册》,在安全标准局指导下由低温液体安全处理联合委员会制订的。     

大型低温液体贮罐管路应力分析

针对使用传统的经验设计方法难以对大型低温液体贮罐管路所受载荷进行分析评定的情况,采用有限元分析方法,实现了对低温贮罐管路系统的温差、压力、重力以及基座沉降、管口等载荷的应力分析.详细分析了管路载荷分布情况和工况,特别针对-196℃/65℃设计范围的液氧贮罐管路,利用I-deas软件建立空间模型和壳单元网格,分析得到不锈钢材料管路系统温差、压力等载荷产生的应力分布情况,并得出温差应力是大型低温液体贮罐管路系统影响最大的载荷应力,同时得出管路弯头部位应力最大的结论,与实际情况完全吻合.     

关于压力容器用安全阀问题的分析

安全阀是一种由进口静压开启的自动泄压防护装置，它是压力容器最为重要的安全附件之一，它的功能是：当容器内压力超过某一定值时，依靠介质自身的压力自动开启阀门，迅速排出一定数量的介质。当容器内的压力降到允许值时，阀又自动关闭，使容器内压力始终低于允许压力的上限，自动防止因超压而可能出现的事故，所以安全阀又被称为压力容器的最终保护装置。安全阀作为一种安全泄放装置，在压力容器上已被广泛应用：     

大型常压低温液体贮槽的设计及发展

从工艺流程、结构设计、力学计算、技术要领等方面阐明了大型常压低温液体贮槽设计、制造的诸多问题 ,特别是就如何保证大型常压低温液体贮槽的可靠性、先进性的关键问题作了一些分析。并简述了发展前景     

Development of No-Vent™ liquid hydrogen storage system for space applications

A number of technological advances required to store and maintain normal-boiling-point and densified cryogenic liquids, including liquid hydrogen, under zero boil-off conditions in-space, for long periods of time, have been developed. These technologies include (1) thermally optimized compact cryogen storage systems that reduce environmental heat leak to the lowest-temperature cryogen, which minimizes cryocooler size and input power, and (2) actively-cooled shields that surround the storage systems and intercept heat leak. The processes and tools used to develop these technologies are discussed. A zero boil-off liquid hydrogen storage system technology demonstrator for validating the actively-cooled shield technology is presented.     

Three-dimensional analysis for liquid hydrogen in a cryogenic storage tank with heat pipe–pump system

This paper presents a study on fluid flow and heat transfer of liquid hydrogen in a zero boil-off cryogenic storage tank in a microgravity environment. The storage tank is equipped with an active cooling system consisting of a heat pipe and a pump–nozzle unit. The pump collects cryogen at its inlet and discharges it through its nozzle onto the evaporator section of the heat pipe in order to prevent the cryogen from boiling off due to the heat leaking through the tank wall from the surroundings. A three-dimensional (3-D) finite element model is employed in a set of numerical simulations to solve for velocity and temperature fields of liquid hydrogen in steady state. Complex structures of 3-D velocity and temperature distributions determined from the model are presented. Simulations with an axisymmetric model were also performed for comparison. Parametric study results from both models predict that as the speed of the cryogenic fluid discharged from the nozzle increases, the mean or bulk cryogenic fluid speed increases linearly and the maximum temperature within the cryogenic fluid decreases.     

A novel cooling scheme for superconducting power cables

Long distance transmission of electrical power with superconducting cables is likely necessary for energy conservation and effective utilization of renewable energy sources. The performance and cost of such superconducting lines is as significantly influenced by cryogenic issues as by superconductor performance. One significant cryogenic issue is that in the usual method of cooling using sub-cooled cryogen flow there is a limited cable length before the cryogen needs to be re-cooled. This adds complexity and cost to the cable system. Here we address this problem by utilizing the latent heat of the cryogen without the complication of multi-phase flow. The cryogen is distributed to the superconducting components by spraying it through small holes in a pressurized line. The pressurized liquid exiting the holes turns into mixed liquid and vapor with a temperature near the boiling point of the cryogen at the pressure of the space surrounding the superconducting components. The pressure in the space surrounding the superconducting components is then kept near atmospheric by maintaining short distances to a vent. The sprayed liquid accumulates but rapidly vaporizes in response to the heat load, providing even cooling power at a fixed temperature for the entire length of the line. Our work indicates that it may be possible to implement a cooling system with much simplified cryogenic stations at the cable ends and allowing cable lengths of up to 100 km with no intermediate cooling stations.     

Magnetic levitation technology and its applications in exploration projects

An energy efficient cryogenic transfer line with magnetic suspension has been prototyped and cryogenically tested. The prototype transfer line exhibits cryogen saving potential of 30–35% in its suspension state as compared to its solid support state. Key technologies developed include novel magnetic levitation using multiple-pole high temperature superconductor (HTS) and rare earth permanent-magnet (PM) elements and a smart cryogenic actuator as the warm support structure. These technologies have vast applications in extremely low thermal leak cryogenic storage/delivery containers, superconducting magnetic bearings, smart thermal switches, etc. This paper reviews the development work and discusses future applications of established technologies.     

关于在用低温液体贮运容器夹层真空度的探讨

简述了我国低温贮运容器真空度判定标准的基本情况。根据《在用压力容器检验规程》中“合于使用”的原则 ,对合理地确定定期检验中夹层真空度的合格标准以及保证低温容器安全使用做了分析和探讨。指出 :以制造标准给定的封结真空度作为定检时的合格标准 ,不合理 ;每台低温容器的真空度降低速率不同 ,导致了真空度的判定标准不同。     

Development of mechanical cryocoolers for the Japanese IR space telescope SPICA

The next Japanese infrared space telescope SPICA features a large 3.5-m-diameter primary mirror and an optical bench cooled to 4.5 K with advanced mechanical cryocoolers and effective radiant cooling instead of using a massive and short-lived cryogen system. To obtain a sufficient thermal design margin for the cryogenic system, cryocoolers for 20 K, 4 K, and 1 K have been modified for higher reliability and higher cooling power. The latest results show that all mechanical cryocoolers achieve sufficient cooling capacity for the cooling requirement of the telescope and detectors on the optical bench at the beginning of life. Consequently, the feasibility of the SPICA cryogenic system concept was validated, while attempts to achieve higher reliability, higher cooling capacity and less vibration have continued for stable operations at the end of life.     

Study on effect of liquid level on the heat leak into vertical cryogenic vessels

The diminishing of heat leak into cryogenic vessels can prolong the storage time of cryogenic liquid. With the storage of cryogenic liquid reducing, the heat leak decreases, while the actual storage time increases. Compared with the theoretical analysis, the numerical simulation can more accurately calculate the heat transfer and temperature distribution in the vessel with complex structure. In this paper the steady state heat leak into cryogenic vessels with different liquid level height is analyzed using a finite element model. And liquid nitrogen boil-off method was adopted in experiments to validate the result of numerical simulation. Experimental results indicate favorable agreement with numerical simulation by ANSYS software. The effect of liquid level on heat leak into the cryogenic vessel can be considered in calculation of storage time and structure design.     

Cryogenic Mass Gauging in a Free-Falling Storage Tank

The most efficient shuttle would be an all-cryogenic propellant vehicle. One problem with on-board cryogenic storage is mass gauging. Even though, in principle, one can determine the amount of cryogen in a tank by its history of use, this is not practical. In free-fall, the exact configuration of the liquid and vapor in the tank is not known. Depending on the recent motion of the craft, the liquid could be in small, dispersed drops, a single glob, or some combination of these configurations. The configuration is known only when the vehicle is under significant acceleration, when a standard level meter may be used to detect the single liquid/vapor meniscus. Currently, the shuttle must be accelerated for 15 sec to make an accurate measurement of propellant volume remaining. We have considered various methods for determining the mass of liquid directly, and have pursued a technique that takes advantage of the large difference in specific heat capacity of liquid and gaseous hydrogen, both of which are nearly independent of the vehicle's motion and position with respect to any gravitational field. Small thermometers and heaters have been utilized that are rapidly responding and possess the necessary sensitivity to make a measurement in a 2,500 liter tank. System design criteria, with sensor construction, are discussed. Data on sensor sensitivity is presented.