Performance of low-friction coatings in helium environments

The aim of this research work was to investigate the possibility of replacing soft PTFE‐based coatings on components operating in helium atmosphere. Focus was on maintaining low friction and improving surface wear resistance. Therefore two commercial DLC coatings (a-C:H and Me-C:H), CrN coating and reference PTFE‐based Rulon and Xylan coatings were included in this investigation. Coatings were deposited on hardened 100Cr6‐bearing steel discs and tested against uncoated steel balls in pin-on-disc contact configuration under dry reciprocating and unidirectional sliding in helium atmosphere. Investigation was concentrated on the effect of running-in, contact pressure, sliding speed and counter-material type and surface treatment on the tribological behaviour of hydrogenated DLC coatings when running‐in in helium.     

An identification study of vermiculites and micas: Adsorption of metal ions in aqueous solution

This study deals with the identification of vermiculite in the presence of mica. Three natural silicates were first subjected to expansion by rapid heat treated at 400 °C. Then, the starting silicates and their derived heat-treated products were analyzed by X-ray diffraction, FT-IR spectroscopy, N₂ adsorption at − 196 °C, and helium density measurement. The adsorption of cadmium, chromium, and lead was also carried out. Two of the silicates are composed of mainly biotite and the other of biotite and vermiculite. In general, the results of X-ray diffraction, FT-IR spectroscopy, and helium density measurements are well in agreement. The heat treatment at 400 °C has little effect on the chemical composition, structure, and texture of the silicates. The development of microporosity is small in the silicates. Surprisingly, the adsorption capacity toward chromium and lead is larger for the biotite silicate than for the vermiculite containing silicate.     

锆复合板换热器制造工艺技术

介绍了锆复合板换热器制造特点和技术难点,在实际制造中,通过详细的试验对比,制定了合理的加工技术参数,为下一步大型锆复合板容器的制造提供了依据。     

冰箱制冷系统检漏方法探讨

总结了冰箱制冷系统检漏经验,并参考了国外先进的检漏方法,提出在冰箱制造过程中,除制冷系统注入F_(12)后的管路焊口用卤素仪检漏外,系统的其他零部件和连接管路焊口都应当采用氮质谱仪检漏。本文介绍了冰箱制冷系统的几种检漏方法及其比较,还介绍了国外目前生产的以氦质谱仪为核心的几种检漏设备。     

钚材料的α能谱以及氦气累积的蒙特卡罗计算

本文根据钚材料的元素成分和放射性核素的级联衰变规律,编程计算了共涉及11种核素杂质以及氦气的生成。采用蒙特卡罗方法计算,得到了自辐照α粒子能谱及其演化规律。在编制的计算程序中设计了独立的随机数发生器,并利用Fortran95的MODULE功能进行模块化封装。这一以封装模块为主体的程序具有良好的通用性和扩展性,可方便地作为一个功能实现部分嵌入钚材料老化研究的其他程序之中。     

用WIP电子枪的小型高重复频率电子束加速器

本文叙述了所研制的一台小型高重复频率电子束加速器装置。该装置的设计指标为:输出电子束能量:120--150keV;电子束流强:5--50A;脉宽:1s;重复频率:100Hz;电子束截面积:550cm2。本加速器的主体是具有独特优点的WIP电子枪。本文着重分析了这种电子枪的工作原理和物理过程,并给出初步实验结果。     

Critical concentration of helium making hydrogen–oxygen with various fractions nonflammable

The objective of this study is to determine the critical concentrations of helium making hydrogen–oxygen nonflammable under various volume fraction ratios of hydrogen and oxygen. Tests were conducted for three volume fraction ratios of hydrogen and oxygen 2:1, 1:1 and 1:2, at the initial pressures of 0.1, 0.2, 0.3 and 0.4 MPa and the initial temperatures of 21, 40, 60, 75 and 90 °C. The flammability limits of mixtures with the lower volume fraction ratios between hydrogen and oxygen are much different from the lower flammability limits of hydrogen in oxygen or air. Compared with the lower flammability limits of hydrogen in oxygen or air, the critical concentrations of helium determined in this study are significant for process safety of the mixtures with various volume fraction ratios between hydrogen and oxygen. For the mixtures at 21 °C, the critical concentrations of helium making hydrogen–oxygen nonflammable increase with the volume fraction ratios of hydrogen and oxygen in the range from 0.5 to 2. The variation of the critical concentrations of helium with the initial pressure depends on the initial temperature. For the mixtures at the initial temperature of 60 °C and the initial pressure of 0.3 MPa, the critical concentration of helium reaches to its limit of 95% in the case of volume fraction ratio of hydrogen and oxygen 2:1. The limit values of the critical concentration of helium are 93% for 1:1 volume fraction ratio of hydrogen and oxygen and 89% for 1:2 volume fraction ratio of hydrogen and oxygen ratio, respectively.     

Dimensional analysis for Gorter-Mellink counter flow convection in pressurized superfluid helium

Dimensional analysis of the heat transport through ducts filled with saturated He II is extended to pressurized conditions up to 20 bar. Simplified models are also presented for the ease of first order estimation of the GM-transport heat flux density, the temperature gradient and the limiting heat flux densities by relating calculations to reduced thermo physical properties, with respect to the properties at the lambda point. The data available show good support for the dimensionless GM-equation in pressurized He II within data scatter and thermo physical property uncertainty.     

Helium dispersion following release in a 1/4-scale two-car residential garage

A series of experiments are described in which helium was released at a constant rate into a 1.5 m × 1.5 m × 0.75 m enclosure designed as a 1/4-scale model of a two-car garage. The purpose was to provide reference datasets for testing and validating computational fluid dynamics (CFD) models and to experimentally characterize the effects of a number of variables on the mixing behavior within an enclosure and the exchange of helium with the outside surroundings. Helium was used as a surrogate for hydrogen, and the total volume released was scaled as the amount that would be released by a typical hydrogen-fueled automobile with a full tank. Temporal profiles of helium were measured at seven vertical locations within the enclosure during and following 1-h and 4-h releases. Idealized vents in one wall sized to provide air exchange rates typical of actual garages were used. The effects of vent size, number, and location were investigated using three different vent combinations. The dependence on leak location was considered by releasing helium at three different points within the enclosure.