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为满足某飞秒激光实验需要,研制了一套低温系统,该系统由真空腔体和制冷系统组成,制冷系统冷源为液氮或液氦。在实验晶体样品的周围使用4个并联电阻加热片提供加热功率,通过PID控制策略,可以将晶体温度控制在5—300 K范围内的任何点。除此之外,该低温系统引入了柔性的输液和排气管路,能够保证晶体在二维移动平台控制下实现一定范围内的移动和转动。介绍了整个真空低温系统的组成,并对系统漏热和晶体温度分布进行了数值模拟,完成了温度测量与控制实验。实验结果表明,通过采用冷气体调节与PID组合的控制策略,当在5—80 K内使用液氦作为冷源时,晶体温度的波动小于0.9 K,当在80—300 K内使用液氮作为冷源时,晶体温度波动小于1.3 K。 相似文献
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一、设计理由 在科研与生产中经常需要将低温液体如液氮从杜瓦瓶等低温容器中输入到低温设备 (如冷阱)中,此项工作在许多单位仍处在手工操作阶段,这样不但不经济,而且易产生危险。为了克服以上存在的问题,达到自动输送液氮的目的,我们设计TS—1型液氮输送器。 二、技术指标 1.液氮流量:0—100升/小时(可调); 2.气源压力:l—2公斤/厘米2; 3.表头压力:0.3—0.6公斤/厘米2。 三、工作原理 利用气源的气体压力作用在低温容器内液氮的液面上。在压差的作用下将液氮压入出液管,再由输液管送往冷阱或其他需用液氮的容器内。 四、结构 S—1型液氮… 相似文献
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真空冷却技术具有降温速度快、运行能耗低等优点,在食品冷链中得到了应用并迅速发展。本文以蒸煮肉制品为研究对象,开展蒸煮肉制品真空冷却效果实验,分析不同冷阱温度对冷却速率、质量变化和真空室内压力对冷却效果的影响。结果表明:不同的冷阱温度对蒸煮肉制品冷却速率、冷却前后的质量变化,以及对冷却过程中真空室内的压力产生不同的影响。另外,并非冷阱温度越低冷却效果越好,实验对比了冷阱温度为-15℃、-25℃和-35℃下的真空冷却过程,冷阱温度的最佳值为-25℃,冷却时间最少为320s。 相似文献
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本文介绍了超高真空校准装置用的液氦低温冷凝泵的性能。 该泵的特点是泵体的双层外壁用液氮冷却作为液氮屏蔽,而未采用泵内的液氮屏蔽挡板。极限真空度高,抽速大,满足了校准装置的要求。 液氮低温冷凝泵在4.2K时测得极限真空为1.2 ×10~-12托,抽速为6500升/秒(对干燥氮气)。减压降温接近2K时,极限真空为 10~-13托,对氢气抽速为11000升/秒。 一、引言 低温冷凝泵是利用致冷剂将固体表面冷到极低温度,使气体碰在冷凝表面上被凝结,从而产生抽气作用的。这种抽气过程基本上是一种物理吸附过程。它的抽速仅与低温表面或低温板的面积、几何形… 相似文献
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由简单可靠的铝片密封垫圈引导出几个新的技术。这种密封垫圈的使用温度允许由液氮温度到450℃这样宽的范围。铝片密封垫圈用在一十50升铝制容器上之去气特性已被研究过了。容器烘烤至240℃。气体之成份及发生率是在有液氮冷阱的系统中,附带或不带钼收集器情况下测定的。冷阱,收集器及阀分别烘烤至400℃,以扩散泵抽气的典型真空系统在10-10乇数量级内压强完全没有波动,这是因为采用了特殊的沸石托转泵,此泵在低真空抽气时,还兼作阱之用,从而避免了机械泵的污染。 相似文献
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中子慢化器低温及真空性能测试系统,用于验证中国散裂中子源氢慢化器的低温性能和真空密封性。此套系统由供液系统、气体加热系统、流量控制系统、温度与压力监测系统组成,采用液氮替代液氢作为测试介质,通过加热器对液氮直接加热的方式获得低温氮气。每根输液管道都是独立的真空单元,配有真空抽口,采用双层不锈钢管道,管道之间做绝热处理。通过控制加热器与内管的装配精度来保证气体换热效率。使用Lakeshore Model 336温控仪和TELEDYNE HASTINGS流量控制器进行气体温度和流量调节。该系统气体输出温度精度达到±5 K,气体输出流量约500 L/min±10%。此套系统不仅为大型低温系统提供安全可靠的低温测试工作介质,同时节约了实验成本,将来在航空航天领域能得以应用推广。 相似文献
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中子慢化器低温及真空性能测试系统,用于验证中国散裂中子源氢慢化器的低温性能和真空密封性。此套系统由供液系统、气体加热系统、流量控制系统、温度与压力监测系统组成,采用液氮替代液氢作为测试介质,通过加热器对液氮直接加热的方式获得低温氮气。每根输液管道都是独立的真空单元,配有真空抽口,采用双层不锈钢管道,管道之间做绝热处理。通过控制加热器与内管的装配精度来保证气体换热效率。使用Lakeshore Model 336温控仪和TELEDYNE HASTINGS流量控制器进行气体温度和流量调节。该系统气体输出温度精度达到±5 K,气体输出流量约500 L/min±10%。此套系统不仅为大型低温系统提供安全可靠的低温测试工作介质,同时节约了实验成本,将来在航空航天领域能得以应用推广。 相似文献
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为了减小现场环境与校准环境的差异对真空漏孔校准的影响,通过理论研究,设计了现场真空漏孔校准装置,可实现对真空漏孔的现场校准。考虑到现场真空漏孔校准装置需便于携带及搬运,装置的设计采用了分体式结构。现场真空漏孔校准装置由抽气系统、校准室系统、真空漏孔连接系统、流量输出系统、充气系统、定容室与压力测量系统及烘烤系统等7个部分组成,复合了定容法及固定流导法两种校准方法,预计真空漏孔校准范围为5×10-10~5×10-5 Pa?m3/s,合成标准不确定度为10%。 相似文献
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Bugnon P Laurenczy G Ducommun Y Sauvageat PY Merbach AE Ith R Tschanz R Doludda M Bergbauer R Grell E 《Analytical chemistry》1996,68(17):3045-3049
The development of a stopped-flow instrument that operates over a temperature range of -40 to +100 °C and up to 200 MPa is described. The system has been designed so that measurements can be performed in absorbance and fluorescence modes simultaneously, without dismantling the unit. It can easily be combined with an optical system of a conventional ambient pressure setup by using light guides. Optimum optical performance and a wide operating wavelength range (220-850 nm) are achieved as the light is not passing through the pressurizing fluid. A special design for the pistons has been developed; thus, the apparatus has proven to be leak-free, even under extreme conditions (high pressure, low temperature, various solvents). The dead time of the system is found to be less than 2 ms at 298 K and is pressure independent up to 200 MPa. We examined the kinetics for the formation of the Mg(2+)-8-hydroxyquinoline chelate in aqueous solutions at pH 8.0 in order to develop a convenient alternative test method for high-pressure stopped-flow spectrometers with absorption and fluorescence detection. 相似文献
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电子激励脱附(ESD)效应和软X射线效应是影响电离真空计测量下限的两大重要因素。基于能量分析器研制了电离真空规,在极高真空校准装置上对其开展性能研究,包括不同压力或不同阴极发射电流下的离子流、ESD效应和软X射线影响。结果表明,系统压力介于10-8Pa和10-6 Pa之间,当气体发生电离,能量分析器电压在低于阳极电压约25 V时收集极能得到最大的气相离子流。系统压力在10-7~10-8 Pa量级,采用2.5 mA的发射电流可得到比1 mA更大的气相离子流值。分离气相离子与ESD离子的能量筒电压差约为30 V,规管栅极除气后可降低ESD效应至除气前的37.5%。电离规的软X射线带来的本底干扰对应等效压力约为9×10-11 Pa。 相似文献
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Stephanie L. Outcalt Byung-Chul Lee 《Journal of research of the National Institute of Standards and Technology》2004,109(6):525-531
An apparatus has been designed and constructed for the measurement of vapor-liquid equilibrium properties. The main components of the apparatus consist of an equilibrium cell and a vapor circulation pump. The cell and all of the system valves are housed inside a temperature controlled, insulated aluminum block. The temperature range of the apparatus is 260 K to 380 K to pressures of 6 MPa. The uncertainty of the temperature measurement is 0.03 K, and the uncertainty in the pressure measurement is 9.8 × 10−4 MPa. An automated data acquisition system is used to measure temperature and pressure at equilibrium. The apparatus has been performance tested by measuring the vapor pressures of propane, butane, and a standard mixture of propane + butane. 相似文献
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T. Kugler B. Jäger E. Bich M. H. Rausch A. P. Fröba 《International Journal of Thermophysics》2013,34(1):47-63
The paper reports on experimental binary diffusion coefficient data of neon–argon gas mixtures. Measurements were performed in the temperature range between 293.15 K and 333.15 K and for pressures between 1 bar and 10 bar over almost the whole composition range using a Loschmidt diffusion cell combined with holographic interferometry. The thermostated Loschmidt cell is divided into two half-cells, which can be separated and connected by a sliding plate. Prior to the measurements, two different pure gases are filled into the two half-cells. After starting the diffusion process, the temporal change of the partial molar densities, or rather of the refractive index of the gases, is detected in both half-cells using two holographic interferometers. With this apparatus, the temperature, pressure, and concentration dependence of the binary diffusion coefficient can be determined. The relative uncertainty of a diffusion measurement is between 0.4 % and 1.4 % depending on the pressure. The experimental data are compared with data from the literature and with new theoretical data based on quantum-mechanical ab initio calculations combined with the kinetic theory of gases. Due to a systematic error, the concentration dependence determined in the upper half-cell shows deviations from the theoretical values and from most of the literature data. The concentration, temperature, and pressure dependence obtained from the data from the lower half-cell, however, are in very good agreement with available data. The product of the binary gas diffusion coefficient and the molar density of the gas mixture shows no significant dependence on pressure for the studied neon–argon noble gas system. 相似文献
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The paper presented experimental investigation on the heat transfer of MLI with different rarefied gases at different pressures. The investigations were carried out using an innovative static liquid nitrogen boil-off rate measurement system in the case of the small temperature perturbations of cold and warm boundaries. The heat fluxes for a number of inert and some polyatomic gases have been analyzed at different heat transfer conditions ranging from molecular to continuum regime, apparent thermal conductivities of the multilayer insulation were measured over a wide range of temperature (77 K–300 K) and pressure (10−3–105 Pa) using the apparatus. The experimental results indicated that under degraded vacuum condition, the influences of rarefied gas on the MLI thermal performance very depend on the gas rarefaction degree which impacted by the MLI vacuum degree. Under the condition of molecular regime heat transfer, the MLI thermal performance was greatly influenced by gas energy accommodation coefficients (EAC), when under the continuum regime, the performances depend on the thermal conductivity of rarefied gas itself. Compared to the results of N2, Ar, CO2, Air and He as interstitial gases in the MLI, Ar was the better selection as space gas because of its low EAC and thermal conductivity characteristics on the different vacuum condition ranging from high pressure to vacuum. So different residual gases can be utilized according to the vacuum level and gas energy accommodation coefficient, in order to improve the insulation performance of low vacuum MLI. 相似文献