高精度单浮子磁悬浮密度测量系统研制

研制了一套高精度的流体压力-密度-温度(p,ρ,T)测量系统,其适用温度、压力和密度范围分别为90—290 K,0—3 MPa,0—2 000 kg/m3。该系统基于阿基米德原理,采用单浮子磁选耦合力传递方法,实现密度的高精度测量。该系统的温度、压力测量标准不确定度分别为5 mK、250 Pa(1.5 MPa量程)/390 Pa(3 MPa量程),密度测量最大相对标准不确定度为0.1%。用新研制的密度测量系统,对190—276 K温度区间和0—3 MPa压力区间的甲烷气体密度进行了测量,实验结果与REFPROP密度值有较好的一致性,验证了该系统的可靠性。     

热真空低温环境实验台研制

为满足低温实验的环境要求,建设了液氮温度级别(80 K)的热真空冷阱低温环境实验台,可进行低温实验中压力与压差、温度与温差、流量与热负荷的测量.该实验台采用附加液氮冷阱的真空多层绝热结构,冷阱温度最低可达80 K,无负载时冷箱真空度可达0.000 03 Pa;在采用外循环工质时,测试压力范围为0-1 MPa、压差范围为...     

Investigation of the Ice–Water Vapor Equilibrium Along the Sublimation Line

An accurate knowledge of the thermodynamic properties of water at low temperature plays an important role in atmospheric processes, chemical physics, and metrological applications. Preliminary investigations of the water vapor?Cice equilibrium along the sublimation line have been carried out at Istituto Nazionale di Ricerca Metrologica (INRIM). The measurements covered the temperature range from ?50?°C to 0?°C, corresponding to a saturation vapor pressure from about 4?Pa to 611?Pa. The measurements were performed using a small gold-plated cell kept in a liquid bath at a constant temperature with millikelvin stability. The sample cell was connected to a manifold where the pressure was measured using two capacitive diaphragm pressure gauges. The paper reports the water sample preparation, measuring method, and measurement corrections. Measurement results are discussed and uncertainty sources estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.038 % at 0?°C to 0.70 % at ?50?°C.     

Experimental study of the influences of degraded vacuum on multilayer insulation blankets

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.     

Absolute measurement of the thermal conductivity of propylene carbonate by the AC transient hot-wire technique

The paper describes a new apparatus for measuring the thermal conductivity of liquids based on a transient hot-wire method. The apparatus has been used to measure the thermal conductivity of propylene carbonate (C₄H₆O₃). The measurements have been carried out in the temperature range 284–313 K and at saturation pressure. The accuracy of the data is within ±1.5%.     

Vapor pressure of difluoromethane (HFC-32)

A slightly modified Burnett apparatus has been used to measure 32 vapor-pressure data for HFC-32 in the temperature range from 273.39 to 347.29 K. The uncertainties of temperature and pressure are estimated to be within ±10 mK and ±500 Pa, respectively. The purity of the sample used in this work is 99.95%. On the basis of our data and of data from the literature, a vapor-pressure equation for HFC-32 is also proposed.     

Realization of the 3He Vapor-Pressure Temperature Scale and Development of a Liquid-He-Free Calibration Apparatus

The ³He vapor-pressure temperature scale was realized using an apparatus based on a continuously operating ³He cryostat at the National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST). The cryostat has two operational modes: a ³He circulation mode and a 1 K pot mode. The ³He circulation mode can be used for ³He vapor-pressure measurements below 1.6 K, and the 1 K pot mode can be used for measurements above 1.3 K. Either mode can be selected for measurements from 1.3 K to 1.6 K. The realization of the ³He vapor-pressure temperature scale in this study fully covers its defined temperature range from 0.65 K to 3.2 K in the International Temperature Scale of 1990. The latest realization results are presented in this article. In addition, a liquid-He-free calibration apparatus was developed. It does not require liquid helium as a cryogen, which usually entails cumbersome handling and periodic refilling. The apparatus was designed for the calibration of capsule-type resistance thermometers from 0.65 K to 24.5561 K (the triple point of neon). The cooling system of the apparatus consists of a commercially available pulse-tube refrigerator and a ³He Joule?CThomson (JT) cooling circuit developed at NMIJ/AIST. The pulse-tube refrigerator is used in a pre-cooling stage and cools the apparatus to approximately 5 K. The ³He JT cooling circuit is used to cool the apparatus from 5 K to below 0.65 K. Since the ³He JT cooling circuit is a closed circuit, the apparatus can run continuously with only simple maintenance required. The basic characteristics of the apparatus are described.     

The thermal conductivity of molten NaNO3 and KNO3

The thermal conductivity data for molten NaNO₃ and KNO₃ have been examined in order to propose recommended data sets for these two popular heat carriers and to establish the reference values above the temperature range covered by toluene and water. It is known that the measurement of the thermal conductivity of molten salts is very difficult, owing mainly to their corrosiveness and high melting temperatures, which introduce complications in apparatus design and significant systematic errors due to radiation and convection. However, some recent measurements seem to manifest more trustworthy values than obtained before. All available data have been collected and critically evaluated. The temperature range covered is 584 to 662 K for molten NaNO₃ and 662 to 712 K for molten KNO₃, with the confidence limits better than ± 5%.     

An apparatus for accurate determinations of vapour-liquid equilibrium properties and gas PVT properties

A precision apparatus for the experimental determination of vapour-liquid equilibrium properties and PVT properties of gas mixtures has been constructed and thoroughly tested. The apparatus used in the phase equilibrium determinations is of the vapour recirculation type, and that used in the PVT measurements is a Burnett apparatus.The experiments may be performed in the temperature range ?180 to +25°C, the temperature being controlled to the nearest ±0.01°C. The temperature can be measured to the nearest 0.01 K using a high precision ac bridge and a calibrated resistance thermometer. The pressure range is from 3 to 350 atm (1 atm = 101.3 kN m^?2) on the vapour recirculation apparatus and up to 700 atm on the Burnett apparatus; the pressure is determined with a dead weight piston gauge, which has an accuracy of 0.01% of the reading or 0.005 lb in^?2, whichever is the greatest. The composition of the gas and liquid phases is determined using a carefully calibrated gas chromotograph. Both the gas and the liquid samples are injected directly into the carrier gas of the gas chromatograph.     

X-ray technique for observation of ice lens growth in partially frozen,saturated soil

This paper reports observations on ice lens growth in partially frozen, saturated soil, and applications for the measurement of hydraulic conductivity in the frozen zone. The authors developed an experimental apparatus using an X-ray technique to observe the ice lens growth and measure the amount of dilatation due to the ice segregation in the sample (Yoneyama et al., 1983). The water flow rate was determined with the displacement of the lead spheres embedded in the sample under several overburden pressures and temperature gradients. The hydraulic conductivity in the frozen zone of the sample was calculated from the water flow rates in the frozen zone under the assumptions that (1) the water flow in the frozen zone could be described by the Darcy flow equation, (2) the generalized Clapeyron equation could be used to describe temperature-pressure relations and (3) ice pressure was equal to the overburden pressure behind the final ice lens. With decreases within a wider range of lower temperatures (?1 to ?10°C) than has ever been reported, the calculated hydraulic conductivities were found to decrease rapidly from 10^?11 to 10^?13 cm/s. It was also observed that the hydraulic conductivity did not depend greatly on the applied load.     

Development of a Laser Interferometric Dilatometer for Measurements of Thermal Expansion of Solids in the Temperature Range 300 to 1300 K

A laser interferometric dilatometer has been developed for measuring linear thermal expansion coefficients of reference materials for thermal expansion in the temperature range 300 to 1300 K. The dilatometer is based on an optical heterodyne interferometer capable of measuring length change with an uncertainty of 0.6 nm. Linear thermal expansion coefficients of silicon were measured in the temperature range 700 to 1100 K. The performance of the present dilatometer was tested by a comparison between the present data and the data measured with the previous version of the present dilatometer and the data recommended by the Committee on Data for Science and Technology (CODATA). The present data agree well with the recommended values over all the temperature range measured. On the other hand, the present values at lower temperatures are in poor agreement with the previous experimental data. The combined standard uncertainty in the present value at 900 K is estimated to be 1.1×10^–8 K^–1.     

Solid-solid transition temperatures in SrCl2 from differential thermal analyses to 0.6 GPa

The reversible phase transition between the high-temperature, cubic C1 and the low-temperature, orthorhombic C23 polymorphs of SrCl₂ has been investigated by differential thermal analysis under hydrostatic pressure to 0.63 GPa. The C23→C1 transition temperature varies linearly with pressure at the rate of 0.42₄ μK(Pa)^?1 from the highest pressures down to ca. 0.34 GPa, and also linearly with slope 1.73 μK(Pa)^?1 at pressures ?0.26 GPa; the reverse, C1→C23 transition is not observed or deduced ?0.21 GPa. The observed curvature for the C1–C23 phase boundary over the range ?0.26–0.34 GPa, 1000–1050 K can be attributed to intersection with the “diffuse” transition in C1; the latter transition, however, could not be observed unambiguously. Linear extrapolation to 0.1 MPa places the C23→C1 transition near 553 K, which implies that C23 - not C1 - is the stable low-temperature polymorph. The recently-investigated transitions in PbF₂ closely parallel these in in SrCl₂.     

Thermal conductivity of hydrogen for temperatures between 78 and 310 K with pressures to 70 MPa

The paper presents new experimental measurements of the thermal conductivity of hydrogen. The ortho-para compositions covered are normal, near normal, para, and para-rich. The measurements were made with a transient hot wire apparatus. The temperatures covered the range from 78 to 310 K with pressures to 70 MPa and densities from 0 to a maximum of 40 mol · L^–1. For compositions normal and near normal, the isotherms cover the entire range of pressure, and the temperatures are 78, 100, 125, 150, 175, 200, 225, 250, 275, 294, 300, and 310K. The para measurements include eight isotherms at temperatures from 100 to 275 K with intervals of 25 K, pressures to 12 MPa, and densities from 0 to 12 mol · L^–1. Three additional isotherms at 150, 250, and 275 K cover para-rich compositions with para percentages varying from 85 to 72%. For these three isotherms the pressures reach 70 MPa and the density a maximum of 30 mol · L^–1. The data for all compositions are represented by a single thermal conductivity surface. The data are compared with the experimental measurements of others through the new correlation. The precision (2) of the hydrogen measurements is between 0.5 and 0.8% for wire temperature transients of 4 to 5 K, while the accuracy is estimated to be 1.5%.     

Wide-range equation of state for water and steam: Method of construction

A wide-range equation of state for water and steam in analytical form is developed. The equation is valid for moderate and high pressures up to 4 × 10¹² Pa, in particular, explosive and static compression in a wide range of densities. An equation is derived which enables one to calculate the Grueneisen coefficient dependent on specific volume and temperature. A method is suggested which enables one to use the experimental data for the dependences of heat capacity and of isochoric coefficient of temperature pressure increase on specific volume and temperature for calculating the Grueneisen coefficient and internal heat energy.     

A Small-Volume Apparatus for the Measurement of Phase Equilibria

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.     

Spectroscopic measurement of the vapour pressure of ice

We present a laser absorption technique to measure the saturation vapour pressure of hexagonal ice. This method is referenced to the triple-point state of water and uses frequency-stabilized cavity ring-down spectroscopy to probe four rotation-vibration transitions of at wavenumbers near 7180?cm(-1). Laser measurements are made at the output of a temperature-regulated standard humidity generator, which contains ice. The dynamic range of the technique is extended by measuring the relative intensities of three weak/strong transition pairs at fixed ice temperature and humidity concentration. Our results agree with a widely used thermodynamically derived ice vapour pressure correlation over the temperature range 0°C to -70°C to within 0.35 per cent.     

Measurements of the relative permittivity of liquid water at frequencies in the range of 0.1 to 10 kHz and at temperatures between 273.1 and 373.2 K at ambient pressure

The static relative permittivity (dielectric constant) of water has been determined from capacitance measurements at frequencies between 0.1 and 10 kHz, in the temperature range from 273.2 to 373.2 K at ambient pressure. The capacitor used for these measurements was formed from sapphire-insulated concentric cylinders. The specific conductance of the water used was maintained within 20% of the lowest value ever observed, which is better than in all previous experiments in this range. The new data shed some light on a discrepancy between sets of literature data in liquid water between the triple and boiling points.     

Kalibrierdruckerzeugung durch statische Gasexpansion

The method of generating well known calibration pressures by means of static expansion of gases is described and the required mathematical equations are derived in general form for real gases. Temperature effects caused by the expansion process are estimated and compared with experimental data obtained at an expansion apparatus. Thereafter, the experimental measurement of the expansion ratio and the generation of calibration pressures over a wide pressure range are discussed for a specific apparatus. Controlling the temperature by immersing the apparatus in a circulated water bath, the uncertainty contribution due to temperature effects was substantially reduced as compared to conventional apparatuses. The uncertainty budget reveals that this apparatus allows the generation of a pressure of, e.g., 0.1 mbar for various gases with a small relative uncertainty (2σ) of 1 . 10^‐3.     

Absolute measurements of the thermal conductivity of alcohols by the transient hot-wire technique

New absolute measurements of the thermal conductivity of methanol, ethanol, propanol, butanol, pentanol, and hexanol at atmospheric pressure and in the temperature range 290–350 K are reported. The overall uncertainty in the reported thermal conductivity data is estimated to be better than ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. The measurements presented in this paper have been used to develop a consistent theoretically based correlation for the prediction of the thermal conductivity of alcohols. The proposed scheme, based on an extention of the rigid-sphere model, permits the density dependence of the thermal conductivity of alcohols, for temperatures between 290 and 350 K and atmospheric pressure, to be represented successfully by an equation containing just one parameter characteristic of the fluid at each temperature.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

An Investigation of the Thermal Conductivity of Zr–2.5%Nb Reactor Alloy

Experimental data are obtained for the thermal conductivity coefficient of zirconium containing 2.5% niobium. The investigated temperature range of 400 to 1600 K covers the range of existence of hexagonal (alpha-phase) and cubic (beta-phase) structural modifications of the alloy. The low-temperature and high-temperature structures differ by the value of the temperature derivative of the thermal conductivity coefficient. The thermal cycling of sample under vacuum of 10^?3 Pa leads to a gradual decrease in thermal conductivity, which is especially pronounced at low temperatures. The available data on electrical resistance for the alpha-phase region are used to estimate the Lorentz function. The obtained values of Lorentz number are indicative of the predominating part played by the electron mechanism of thermal conductivity in the alloy. The values of thermal conductivity measured for the beta-phase are used to determine the electrical conductivity of the alloy.