Design and development of a helium injection system to improve external leakage detection during liquid nitrogen immersion tests

The testing of assemblies for use in cryogenic systems commonly includes evaluation at or near operating (therefore cryogenic) temperature. Typical assemblies include valves and pumps for use in liquid oxygen-liquid hydrogen rocket engines. One frequently specified method of cryogenic external leakage testing requires the assembly, pressurized with gaseous helium (GHe), be immersed in a bath of liquid nitrogen (LN₂) and allowed to thermally stabilize. Component interfaces are then visually inspected for leakage (bubbles). Unfortunately the liquid nitrogen will be boiling under normal, bench-top, test conditions. This boiling tends to mask even significant leakage.One little known and perhaps under-utilized property of helium is the seemingly counter-intuitive thermodynamic property that when ambient temperature helium is bubbled through boiling LN₂ at a temperature of −195.8 °C, the temperature of the liquid nitrogen will reduce.This paper reports on the design and testing of a novel proof-of-concept helium injection control system confirming that it is possible to reduce the temperature of an LN₂ bath below boiling point through the controlled injection of ambient temperature gaseous helium and then to efficiently maintain a reduced helium flow rate to maintain a stabilized liquid temperature, enabling clear visual observation of components immersed within the LN₂. Helium saturation testing is performed and injection system sizing is discussed.     

Combined heat and mass transfer in natural convection between vertical parallel plates

Abstract

This study is to examine the effects of latent heat transfer associated with liquid film vaporization on heat transfer in the natural convection flows driven by the simultaneous presence of combined buoyancy forces of thermal and mass diffusion. Results are especially presented for an air‐water system under various conditions. The influences of channel length and system temperatures on the momentum, heat and mass transfer in the flow are investigated in great detail. The important role of transport of latent heat of vaporization under the situations of buoyancy‐aiding and opposing flows is clearly demonstrated.     

手持蓄压式液氮冷冻治疗器

本文介绍了一种新型的手持蓄压式液氮冷冻治疗器,它以不锈钢真空绝热瓶做主体,在瓶盖上安装有拉杆柱塞式喷射阀和安全阀等,拉下拉杆,液氮以较大的射流喷出,还能通过各号冷喷冷喷针喷出力度大的细束液氮液,操作便捷,使用安全,治疗效果好,可用于美容,皮肤科,五官科,口腔科,妇科,肿瘤等的冷冻治疗。     

Analysis of mixed-mode interlaminar fracture and damage behavior of GFRP woven laminates at cryogenic temperatures

The objective of this work is to investigate the interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates loaded in a mixed-mode bending (MMB) apparatus at cryogenic temperatures. The finite element analysis (FEA) is used to determine the mixed-mode interlaminar fracture toughness of MMB specimen at room temperature (RT), liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). A FEA coupled with damage is also employed to study the damage distributions within the MMB specimen and to examine the effect of damage on the mixed-mode energy release rate. The technique presented can be efficiently used for characterization of mixed-mode interlaminar fracture and damage behavior of woven laminate specimens at cryogenic temperatures.     

低温液体泵主轴材料的性能试验研究

通过对试验用钢与对比用钢的性能试验,探讨了在规定的热处理状态下马氏体沉淀硬化不锈钢OCr17Ni4Cu4Nb的室温和低温力学性能;指出对0Cr17Ni4Cu4Nb进行固溶和双时效处理是获得最佳低温性能的有效途径;得出了低温液体泵主轴选材应优先选用0Cr17Ni4Cu4Nb钢的结论     

The thermal conductivity of liquid argon for temperatures between 110 and 140 K with pressures to 70 MPa

The paper presents new experimental measurements of the thermal conductivity of liquid argon for four temperatures between 110 and 140 K with pressures to 70 MPa and densities between 23 and 36 mol · L ^–1. The measurements were made with a transient hot-wire apparatus. A curve fit of each isotherm allows comparison of the present results to those of others and to correlations. The results are sufficiently detailed to illustrate several features of the liquid thermal conductivity surface, for example, the dependence of its curvature on density and temperature. If these details are taken into account, the comparisons show the accuracy of the present results to be 1 %. The present results, along with several other sets of data, are recommended for selection as standard thermal conductivity data along the saturated liquid line of argon, extending the standards into the cryogenic temperature range. The results cover a fairly wide range of densities, and we find that a hard-sphere model cannot represent the data within the estimated experimental accuracy.     

UHV sample holder for fast heating and cooling cycles

We describe a UHV sample holder that allows fast heating and cooling cycles between 77 K and 1300 K. The system allows us to perform thermal treatment of a sample. The samples are heated by electron bombardment and the cooldown is achieved by liquid nitrogen (LN₂). The sample holder is designed to be assembled in a multitechnique surface analysis apparatus that performs AES, SIMS, TDS and XPS analysis.     

用于HEPS-TF低温波荡器的过冷液氮循环系统

在高能同步辐射光源验证装置(HEPS-TF)的插入件系统中,将要研制一台基于镨铁硼永磁铁的低温波荡器(CPMU)。低温波荡器要求磁铁磁极阵列工作温度要在85 K以下,同时整个大梁轴向的温度梯度不超过1.5 K/m。经过理论计算,低温波荡器在有束流情况下的热负荷约660 W@80 K。为冷却低温波荡器大梁磁结构,设计了一套过冷液氮闭循环迫流冷却系统。为了确保磁铁有更好的低温效果和温度均匀性,低温波荡器内大梁采用了双通道冷却设计。最后,根据低温流程设计了可行的机械结构,称其为液氮过冷器冷箱。     

Capacitance-based liquid holdup measurement of cryogenic two-phase flow in a nearly-horizontal tube

Liquid holdup measurement of cryogenic fluids is an area of considerable significance because of its inevitable occurrence in LNG transportation, rocket propellant delivery and superconducting equipment cooling, etc. To measure the liquid holdup of cryogenic two-phase flow, a capacitance sensor was carefully designed, which consists of a pair of optimized concave-electrode form with the electric circuit for the small capacitance detection. Four flow patterns were realized to evaluate the performance of the sensor in visualization experiments with liquid nitrogen and vaporous nitrogen. An image method was employed to calibrate the capacitance sensor, which led to a mathematical relationship between the capacitance and the liquid holdup. The results indicated that the obtained correlation between liquid holdup and capacitance satisfactorily coincided with the measured data.     

Cryogenic delamination growth in woven glass/epoxy composite laminates under mixed-mode I/II fatigue loading

This paper investigates the fatigue delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates under mixed-mode I/II conditions at cryogenic temperatures. Fatigue delamination tests were performed with the mixed-mode bending (MMB) test apparatus at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K), in order to obtain the delamination growth rate as a function of the range of the energy release rate, and the dependence of the delamination growth behavior on the temperature and the mixed-mode ratio of mode I and mode II was examined. The energy release rate was evaluated using three-dimensional finite element analysis. The fractographic examinations by scanning electron microscopy (SEM) were also carried out to assess the mixed-mode fatigue delamination growth mechanisms in the woven GFRP laminates at cryogenic temperatures.     

爆炸金属复合材料在低温领域的应用

低温技术的发展推动着爆炸金属复合材料制造技术的进步,从爆炸复合技术原理出发,着重对爆炸金属复合材料在LNG气化器、空气分离设备、液氮生物容器及极地船舶等低温领域应用情况进行了描述,并对未来的市场前景进行了展望。      

液氮浴中不锈钢板动态冷却过程试验及模拟分析

以液氮为介质,通过测量不锈钢平板试件在液氮浴中的动态温度分布,在实测降温曲线同根据经验公式模拟得到的降温曲线进行对比的基础上,对低温沸腾换热过程中临界热流密度和最小膜态沸腾热流密度所对应的温差进行了修正,为更准确地模拟深冷处理中的降温过程提供了指导。利用修正参数对不锈钢平板进行了模拟分析。     

有效导热系数对低温容器日蒸发率的影响

低温容器是气体液化分离加工工业中的重要设备，绝热设计是低温容器设计的重要组成部分，它直接影响低温容器的日蒸发率。在不同的绝热材料和一定漏热温差的条件下，给出了普通绝热和真空粉末绝热型低温容器的日蒸发率与热材料的有效导热系数以及绝热层厚度之间的关系曲线。为简化设计和比较低温容器的特性提供方法和依据。     

移动式充氧(氮)槽车研制的技术关键

00L/h移动式充氧 (氮 )槽车是首台国产气液两用高压充氧设备 ,技术要求高 ,研制难度大。介绍了该车研制项目组在降低蒸发率、低温液体泵的选用、设备的安全性、维修性等方面的技术关键及解决措施。     

Influence of cryogenic thermal treatment on mechanical properties of an Al–Cu–Mg alloy

In this study, a cryogenic thermal treatment is developed and its effects on mechanical properties and precipitates are investigated. Water-quenched samples were immersed in liquid nitrogen and reheated in hot oil at 180°C or boiling water for 5?min. Finally, the samples were artificially aged at 190°C for 12?h. The results indicated a notable increase of about 75?MPa in the ultimate tensile strength in comparison to T6 heat-treated alloy. TEM observations revealed that the S(S′) precipitates were fine and uniformly distributed in the microstructure due to reheating in hot oil and subsequent aging treatment.     

Cryogenic cooling system of HTS transformers by natural convection of subcooled liquid nitrogen

Heat transfer analysis on a newly proposed cryogenic cooling system is performed for HTS transformers to be operated at 63–66 K. In the proposed system, HTS pancake windings are immersed in a liquid nitrogen bath where the liquid is cooled simply by colder copper sheets vertically extended from the coldhead of a cryocooler. Liquid nitrogen in the gap between the windings and the copper sheets develops a circulating flow by buoyancy force in subcooled state. The heat transfer coefficient for natural convection is estimated from the existing engineering correlations, and then the axial temperature distributions are calculated analytically and numerically with taking into account the distributed AC loss in the windings and the thermal radiation on the walls of liquid-vessel. The calculation results show that the warm end of the HTS windings can be maintained at only 2–3 K above the freezing temperature of nitrogen, with acceptable values for the height of HTS windings and the thickness of copper sheets. It is concluded that the cooling by natural convection of subcooled liquid nitrogen can be an excellent option for compactness, efficiency, and reliability of HTS transformers.     

Mixed-mode interlaminar fracture and damage characterization in woven fabric-reinforced glass/epoxy composite laminates at cryogenic temperatures using the finite element and improved test methods

The present research examines experimentally and analytically the mixed-mode interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. The mixed-mode bending (MMB) tests were performed with the improved test apparatus, at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). The energy release rates at the onset of delamination crack propagation were evaluated for the woven GFRP specimens using both beam theory and finite element analysis. The fracture surfaces were also examined to verify the fracture mechanisms. In addition, the initiation and growth of damage in the specimens were predicted by a damage analysis, and the damage effect on the mixed-mode interlaminar fracture properties at cryogenic temperatures was explored.     

Cryogenic turning of the Ti–6Al–4V alloy with modified cutting tool inserts

Productivity in the machining of titanium alloys is adversely affected by rapid tool wear as a consequence of high cutting zone temperature. Conventional cutting fluids are ineffective in controlling the cutting temperature in the cutting zone. In this research work, an attempt has been made to investigate the effect of liquid nitrogen when it is applied to the rake surface, and the main and auxiliary flank surfaces through holes made in the cutting tool insert during the turning of the Ti–6Al–4V alloy. The cryogenic results of the cutting temperature, cutting forces, surface roughness and tool wear of the modified cutting tool insert have been compared with those of wet machining. It has been observed that in the cryogenic cooling method, the cutting temperature was reduced by 61–66% and the surface roughness was reduced to a maximum of 36% over wet machining. The cutting force was decreased by 35–42% and the flank wear was reduced by 27–39% in cryogenic cooling over that of wet machining. Cryogenic cooling enabled a substantial reduction in the geometry of tool wear through the control of the tool wear mechanisms. The application of liquid nitrogen to the heat generation zones through holes made in the cutting tool insert was considered to be more effective over conventional machining.     

Argon Triple Point for Long-Stem SPRTs: Thermal Behavior

A new device for an ITS-90 triple-point-of-argon realization has been designed at LNE-CNAM. It follows the widely used principle of the cryogenic Dewar filled with pressurized liquid nitrogen, but the new construction achieves better temperature stability at the level of the argon cell. A new pressure regulation, controlled directly by a nitrogen temperature measurement, solves the problem of the influence of atmospheric-pressure variations. The paper presents the new device and the thermal tests conducted in order to optimize the pressure regulation.     

用于低温设备的液氮分配系统

液氮分配系统中包括强制循环系统和重力输送自循环（自然循环）系统,重点介绍重力输送自循环（自然循环）液氮系统的性能和特点,分析出自然循环液氮系统是稳定、可靠、低液氮消耗和较高效率的系统。分配系统降低了工作温度,可以不用液氮泵,减少了系统中的阀门。设计自然循环系统前,要进行系统的热和液压分析,在自然循环系统设计中,系统的分析和预测是非常重要的,因为通过分析和验证才能保证系统内任何地方蒸发率都不超过10％,这可以明显减少设计风险。自然循环液氮系统已在多种低温设备中得到应用。