Climatic Chamber for Temperatures up to 180\,^{\circ }\mathrm{C} and Pressures up to 0.5 MPa

A new relative-humidity setup was developed for calibrating sensors in the temperature range from \(-40\,^{\circ }\mathrm{C}\) up to \(180\,^{\circ }\mathrm{C}\) and at pressures down to 700 hPa and up to 0.5 MPa. The setup is based on the chamber-in-chamber model: a small additional chamber is positioned inside a climatic chamber. While the climatic chamber is used to generate the air temperature, a pre-conditioned gas from outside the climatic chamber delivers the required humidity in the new pressure chamber. Validation of the setup at atmospheric pressure showed relative-humidity uncertainties of 0.2 %rh at 5 %rh over the whole temperature range and 0.4 %rh at 95 %rh for temperatures above \(0\,^{\circ }\mathrm{C}\) . Below \(0\,^{\circ }\mathrm{C}\) , the maximum uncertainty increases to 0.9 %rh due to the influence of the temperature homogeneity. The temperature uncertainty of the new setup is between \(0.10\,^{\circ }\mathrm{C}\) and \(0.21\,^{\circ }\mathrm{C}\) . Five commercially available relative-humidity sensors, of different type and manufacturer and all suitable for high temperatures, were calibrated in the new setup. The measurements showed deviations outside the stated specifications of the manufacturer and the need of traceable calibration facilities.     

Validation of Primary Water Dew-Point Generator for Methane at Pressures up to 6 MPa

In this paper, the validation of the water dew-point generator with methane as a carrier gas in the temperature range from \(-41\,^{\circ }\hbox {C}\) to \(+15\,^{\circ }\hbox {C}\) and at pressures up to 6 MPa is reported. During the validation, the generator was used with both nitrogen and methane to investigate the effect of methane on the generator and the chilled mirror dew-point meters. The effect of changing the flow rate and the dew-point temperature of the gas entering the generator, on the gas exiting the generator was investigated. As expected, methane at high pressures created hydrates in combination with water and low temperatures, thus limiting the temperature range of the generator to \(+8\,^{\circ }\hbox {C}\) to \(+15\,^{\circ }\hbox {C}\) at its maximum operating pressure of 6 MPa. A lower operating pressure extended the temperature range; for example, at 3 MPa, the temperature range was already extended down to \(-15\,^{\circ }\hbox {C}\) , and at 1 MPa, the range was extended down to \(-41\,^{\circ }\hbox {C}\) . The validation showed that, in its operating range, the generator can achieve with methane the same standard uncertainty of \(0.02\,^{\circ }\hbox {C}\) frost/dew point already demonstrated for nitrogen and air carrier gases.     

Measurement of the (p, \rho,T) Properties for Pure Hydrocarbons at Temperatures up to 600 K and Pressures up to 200 MPa

The data available for the thermodynamic properties of propane, \(n\) -butane, and isobutane at temperatures above 440 K are outdated and show significant discrepancies with each other. The ambiguity associated with these data could be limiting to the development of any understanding related to the effects of mixing of these substances with other materials such as \(\text{ CO}_{2}\) , ammonia, and non-flammable or lower-flammable HFC refrigerants. In this study, the (p, \(\rho \) , T) properties of propane, \(n\) -butane, and isobutane were measured at temperatures ranging from (360 to 600) K and pressures ranging from (50 to 200) MPa. Precise measurements were carried out using a metal-bellows variable volumometer with a thermostatted air bath. The expanded uncertainties \((k = 2)\) in the temperature, pressure, and density measurements were estimated to be \(<\) 5 mK, 0.02 MPa, and 0.88 kg  \(\cdot \)  m \(^{-3}\) ( \(T\le 423\)  K, \(p<100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T\le 423\)  K, \(p\ge 100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p < 100\)  MPa), and 2.94 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p \ge 100\)  MPa), respectively. The data obtained throughout this study were systematically compared with the calculated values derived from the available equations of state. These models agree well with the measured data at higher temperatures up to 600 K, demonstrating their suitability for an effective and precise examination of the mixing effects of potential alternative mixtures.     

Speed of Sound in Pure Water at Temperatures between 274 and 394 K and at Pressures up to 90 MPa

A newly designed experimental apparatus has been used to measure the speed of sound u in high-purity water on nine isotherms between 274 and 394 K and at pressures up to 90 MPa. The measurement technique is based on a traditional double-reflector pulse-echo method with a single piezoceramic transducer placed at unequal distances from two stainless steel reflectors. The transit times of an acoustic pulse are measured at a high sampling rate by a digital oscilloscope. The distances between the transducer and the reflectors were obtained at ambient temperature and pressure by direct measurements with a coordinate measuring machine. The speeds of sound are subject to an overall estimated uncertainty of 0.05 %. The acoustic data were combined with available values of density ρ and isobaric heat capacity c_p along one isobar at atmospheric pressure to calculate the same quantities over the whole temperature and pressure range by means of a numerical integration technique. These results were compared with those calculated from the IAPWS-95 formulation with corresponding relative deviations which are within 0.1%. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Thermal Conductivity of Carbon Dioxide–Methane Mixtures at Temperatures Between 300 and 425 K and at Pressures up to 12 MPa

The thermal conductivities of carbon dioxide and three mixtures of carbon dioxide and methane at six nominal temperatures between 300 and 425 K have been measured as a function of pressure up to 12 MPa. The measurements were made with a transient hot-wire apparatus. The relative uncertainty of the reported thermal conductivities at a 95% confidence level is estimated to be ±1.2%. Results of the low-density analysis of the obtained data were used to test expressions for predicting the thermal conductivity of nonpolar mixtures in a dilute-gas limit developed by Schreiber, Vesovic, and Wakeham. The scheme was found to underestimate the experimental thermal conductivity with deviations not exceeding 5%. The dependence of the thermal conductivity on density was used to test the predictive scheme for the thermal conductivity of gas mixtures under pressure suggested by Mason et al. and improved by Vesovic and Wakeham. Comparisons reveal a pronounced critical enhancement on isotherms at 300 and 325 K for mixtures with methane mole fractions of 0.25 and 0.50. For other states, comparisons of the experimental and predicted excess thermal conductivity contributions showed a smaller increase of the experimental data with deviations approaching 3% within the examined range of densities.     

GaAs Schottky Barrier Detectors for Alpha-Particle Spectrometry at Temperatures up to 120°C

Technical Physics Letters - GaAs Schottky barrier detectors for α particle spectrometry have been tested. Detectors had an input window area of 80 mm2 and a working barrier layer thickness of...     

A standard capacitor for frequencies up to 200–300 Mc

Summary The accuracy of determining the effective capacitance of coaxial cylindrical capacitors depends to a great extent on the construction of the connecting device of the instrument to which the capacitor has to be joined. The best junction device is the one which reproduces the construction of the coaxial capacitor. In this instance the error due to an edge field will be minimal and there will be no error at all due to the nonuniformity of the field.     

Viscosity and Thermal Conductivity of 1-Hexyl-3-methylimidazolium Tetrafluoroborate and 1-Octyl-3-methylimidazolium Tetrafluoroborate at Pressures up to 20?MPa

Viscosity and thermal conductivity values are reported for a series of 1-alkyl-3-methylimidazolium tetrafluoroborate compounds with hexyl (1-hexyl-3-methylimidazolium tetrafluoroborate) and octyl (1-octyl-3-methylimidazolium tetrafluoroborate) groups. The viscosity was measured with a rolling-ball viscometer at 293.15 K to 353.15 K and pressures up to 20.0?MPa. The experimental values were correlated with a hybrid VFT–Tait equation. The thermal conductivity was measured using the transient short hot-wire method at 294 K to 335 K and pressures up to 20.0?MPa. The experimental values at 293.15 K and 0.1?MPa agreed with the predicted values proposed by Fr?ba et?al.     

Thermal stability up to 800?°C of a Ni–4?wt% Al nanocomposite

Abstract  

The thermal stability up to 800 °C of a nanocrystalline (NC) Ni (mean grain size ~25 nm) with ~4 wt% Al dispersed in the form of ~160-nm-sized particles, which was fabricated by co-electrodeposition from a nickel sulfate bath, has been investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that microstructural evolution of the composite is temperature dependent, i.e., normal grain growth of the NC Ni, ~0.6 wt% Al solution into the Ni matrix and direct reaction between Al and Ni to form Ni₃Al precipitates occurred at ~290, ~325 and ~575 °C, respectively. The distribution of Al in Ni matrix with temperature is fully discussed.     

Isochoric Heat Capacities of Propane + Isobutane Mixtures at Temperatures from 280 to 420 K and at Pressures to 30 MPa

The isochoric heat capacity (c_v) and pressure–volume–temperature-composition (pvTx) properties were measured for propane + isobutane mixtures in the liquid phase and in the supercritical region. The expanded uncertainty (k = 2) of temperature measurements is estimated to be ±13 mK, and that of pressure measurements is ±8 kPa. The expanded relative uncertainty for c_v is ±3.2% for the liquid phase, increasing to ±4.8% for near-critical densities. The expanded uncertainty for density is estimated to be ±0.16%. The present measurements for {xC₃H₈ +(1−x)i-C₄H₁₀} with x = 0.0, 0.498, 0.756, and 1.0, were obtained at 659 state points at temperatures from 270 to 420 K and at pressures up to 30 MPa. The experimental data were compared with a published equation of state. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Measurements of Vapor Pressures from 280 to 369 K and (p, ρ, T) Properties from 340 to 400 K at Pressures to 200 MPa for Propane

Measurements of (p, ρ, T) properties for compressed liquid propane have been obtained by means of a metal-bellows variable volumometer at temperatures from 340 to 400 K at pressures up to 200 MPa. The volume- fraction purity of the propane sample was 0.9999. The expanded uncertainties (k = 2) of temperature, pressure, and density measurements have been estimated to be less than 3 mK; 1.5 kPa ( MPa), 0.06% (7 MPa MPa), 0.1% (50 MPa MPa) , and 0.2% (p>150 MPa); and 0.11%, respectively. Four (p, ρ, T) measurements at the same temperatures and pressures as literature values have been conducted for comparisons. In addition, vapor pressures were measured at temperatures from 280 to 369 K. Furthermore, comparisons of available equations of state with the present measurements are reported.Paper presented at the 17th European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Density and Viscosity of the 1-Methylnaphthalene+2,2,4,4,6,8,8-Heptamethylnonane System from 293.15 to 353.15 K at Pressures up to 100 MPa

The dynamic viscosity of the binary mixture 1-methylnaphthalene+2,2,4,4,6,8,8-heptamethylnonane was measured in the temperature range 293.15 to 353.15K (in progressive 10K steps) at pressures of 0.1, 20, 40, 60, 80, and 100MPa. The composition of the system is described by nine molar fractions (0 to 1 in 0.125 progressive steps). The density was measured at pressures from 0.1 to 60MPa in progressive 5 MPa steps. The measurements of are used to determine the excess viscosity ^E and the excess activation energy of flow G ^E as a function of pressure, temperature, and composition. Some models have been used to represent the viscosity of this binary mixture.     

Experimental Study of the Velocity of Sound in Liquid n‐Tetradecane at Temperatures from 303.15 to 433.15 K and Pressures to 100 MPa

The velocity of sound in liquid ntetradecane has been studied experimentally in the interval of temperatures from 303 to 433 K and pressures to 100 MPa. The maximum measurement error amounts to 0.1%. Experimental data on the velocity of sound in liquid ntetradecane in the region of the state variables p = 50–100 MPa and T > 373 K have been obtained for the first time. It has been shown that the new data demonstrate the reliability of the structure–property quantitative correlation proposed earlier for the acoustic quantity in the series of nalkanes.     

Burnett PVT Measurements of Hydrogen and the Development of a Virial Equation of State at Pressures up to 100 MPa

PVT properties were measured for hydrogen by the Burnett method in the temperature range from 353 K to 473 K and at pressures up to 100 MPa. In the present Burnett method, the pressure measurement was simplified by using an absolute pressure transducer instead of a differential pressure transducer, which is traditionally used. The experimental procedures become easier, but the absolute pressure transducer is set outside the constant temperature bath because of the difficulty of its use in the bath, and the data acquisition procedure is revised by taking into account the effects of the dead space in the absolute pressure transducer. The measurement uncertainties in temperature, pressure, and density are 20 mK, 28 kPa, and 0.07 % to 0.24 % (k = 2), respectively. Based on the present data and other experimental data at low temperatures, a virial equation of state (EOS) from 220 K to 473 K and up to 100 MPa was developed for hydrogen with uncertainties in density of 0.15 % (k = 2) at P ≤ 15 MPa, 0.20 % at 15 MPa < P ≤ 40 MPa, and 0.24 % at P > 40 MPa, and this EOS shows physically reasonable behavior of the second and third virial coefficients. Isochoric heat capacities were also calculated from the virial EOS and were compared with the latest EOS of hydrogen. The calculated isochoric heat capacities agree well with the latest EOS within 0.5 % above 300 K and up to 100 MPa, while at lower temperatures, as the pressure increases, the deviations become larger (up to 1.5 %).     

Burnett Method with Absolute Pressure Transducer and Measurements for PVT Properties of Nitrogen and Hydrogen up to 473 K and 100?MPa

A measurement method for PVT properties of high-temperature and high-pressure gases was developed by simplifying the Burnett method and revising the data acquisition procedure. Instead of a differential pressure transducer, which is traditionally used, an absolute pressure transducer is used in the present method, and the measurement of pressure becomes easier. However, the absolute pressure transducer is placed outside the constant temperature bath because of the difficulty of its use in high-temperature surroundings, and some parts with different temperatures from the sample vessels exist as dead space. The present method takes into account the effect of the dead space in the data acquisition procedure. Nitrogen was measured in the temperature range from 353 K to 473 K and at pressures up to 100 MPa to determine the apparatus constants, and then, hydrogen was measured at 473 K and up to 100 MPa. The determined densities are in agreement within uncertainties of 0.07% to 0.24% (k = 2), both with the latest equation of state and existing measured data.     

Thermal-Conductivity Measurements of Aqueous Orthophosphoric Acid Solutions in the Temperature Range from (293 to 400) K and at Pressures up to 15 MPa

A new improved guarded parallel-plate thermal-conductivity cell for absolute measurements of corrosive (chemically aggressive) fluids under pressure has been developed. Using the new modified guarded parallel-plate apparatus the thermal conductivity of aqueous orthophosphoric acid solutions was measured over the temperature range from (293 to 400) K and pressures up to 15 MPa. Measurements were made for three compositions of \(\text {H}_{3}\text {PO}_{4}\) (8 mass%, 15 mass%, and 50 mass%) along three isobars of (0.101, 5, and 15) MPa. The combined expanded uncertainty of the thermal-conductivity \((\lambda )\) measurements at the 95 % confidence level with a coverage factor of \(k=2\) is estimated to be 2 %. The uncertainties of the temperature, pressure, and concentration measurements were 15 mK, 0.05 %, and 0.01 %, respectively. The temperature, concentration, and pressure dependences of the thermal conductivity of the solution were studied. The measured values of thermal conductivity were compared with the available reported data and the values calculated from various correlation and prediction models. A new wide-range correlation model (extended Jones–Dole type equation with pressure-dependent coefficients) for the \(\text {H}_{3}\text {PO}_{4}\) (aq) solution was developed using the present experimental data.     

Vapor–Liquid Equilibrium Data for the Sulfur Dioxide (SO<Subscript>2</Subscript>) + Difluoromethane (R32) System at Temperatures from 288.07 to 403.16 K and at Pressures up to 7.31 MPa

Isothermal vapor–liquid equilibrium data have been measured for the binary system R32 (difluoromethane) + SO₂ at eight temperatures between 288.07 and 403.16 K, and at pressures in the range 0.417–7.31 MPa. The experimental method used in this work is of the static–analytic type, taking advantage of two pneumatic capillary samplers (Rolsi^TM, Armines patent) developed in the CENERG/TEP laboratory. The data were measured with uncertainties within ±0.02 K and ±0.0015 MPa, respectively, for temperatures and pressures and ±1% for molar compositions as a result of careful calibrations. The isothermal P, x, y data are well represented with the Peng–Robinson equation of state using the Mathias–Copeman alpha function and the Wong–Sandler mixing rules involving the NRTL model.     

Establishment of High Pressure Pneumatic Standard up to 40?MPa at NPLI

The current paper describes the successful establishment of high pressure pneumatic secondary standard for the realization of national pneumatic pressure scale up to 40?MPa from the previously existing 12?MPa. The traceability as well as the uncertainty in measurement was established through a continuous chain of measurements from very low pressures starting with the ultrasonic interferometer manometer and successive extension in overlapping pressure ranges. For this purpose a piston cylinder assembly designated as NPLI-40, with a pressure range of 0.2?C40?MPa was coupled to a mechanical gas booster through a high gas pressure controller. We have experimentally estimated the zero pressure effective area of piston as well as the distortion coefficient which is traceable to the international system of unit SI. The CMC for the same is now on the BIPM website. The results obtained are discussed in detail.     

Thermo-mechanical properties of Penly reactor envelope at temperatures up to 200°C

This paper reports on an experimental investigation conducted to study the effects of high temperatures of up to 200°C on the phase composition, pore structure development and physico-mechanical properties of concrete at the PENLY nuclear power plant (France). The concrete specimens were manufactured under laboratory conditions from identical materials used at the construction site in PENLY, and then stored at 20°C/100% R.H. for 28 days and exposed to temperatures of 40°C, 60°C, 100°C, 200°C, and 20°C/60%R.H., respectively. Test results revealed that an intense structural integrity degradation of PENLY concrete occurs between 100°C and 200°C due both to a loss of water bound in hydrated cement minerals and to subsequent air void formation. This phenomenon is related to an increase in the median pore radius and total porosity values, as well as to a decrease in the dynamic and static moduli of PENLY concrete. The reduction in volume of the hydrate phase is believed to be the reason behind the rapid expansion, over a short time interval, due to a time-limited moistening of the specimen by released water with a sudden rise in temperature, followed by a stabilised period of shrinkage and creep.