Measurement of the compressibility and sound velocity of neon up to 1 GPa

The density of neon has been determined at 298.15 K as a function of pressure from 80 MPa to 1 GPa. The precision of the measurements is 0.03%, while the estimated absolute accuracy is between 0.05 and 0.09%. The sound velocity has been measured between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.06%. The adiabatic compressibility and the ratio of the specific heats are calculated by combining pVT with velocity-of-sound data at 298 K. Several equations of state are fitted to the density data at 298.15 K.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Measurement of the compressibility and sound velocity of helium up to 1 GPa

By using a gas expansion technique, the density of helium has been determined at 298.15 K as a function of pressure from 100 MPa to 1 GPa. The precision of the measurements is 0.02%, while the estimated absolute accuracy is about 0.08%. The sound velocity has been measured by a phase-comparison pulseecho technique between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.04%. By combining pVT with velocity-of-sound data at 298 K, the adiabatic compressibility and the ratio of the specific heats are calculated. The experimental sound velocities are compared with the values, predicted from an equation of state as proposed by Hansen.     

Compressibility and sound velocity measurements on N2 up to 1 GPa

A gas expansion technique has been used to determine the pVT properties of N₂ up to 1 GPa at 298.15 K, with an accuracy of 0.08% in density, 1 mK in temperature, and 0.05%+0.2 MPa in pressure. The sound velocity has been measured by a phase-comparison pulse-echo technique between 123 and 298 K at intervals of 25 K and at pressures up to 1 GPa, with an accuracy of better than 0.02% in sound velocity, 10 mK in temperature, and 0.05%+0.2 MPa in pressure. An equation of state is presented that correlates the density data over the wide pressure range of 36–1000 MPa with maximum deviations between the calculated and the experimental densities of less than 0.05%.     

An absolute vibrating-wire viscometer for liquids at high pressures

The design and operation of a new vibrating-wire viscometer for the measurement of the viscosity of liquids at pressures up to 100 MPa are described. The design of the instrument is based on a complete theory so that it is possible to make absolute measurements with an associated error of only a few parts in one thousand. Absolute measurements of the viscosity of n-hexane are reported at 298.15 K at pressures up to 80 MPa. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%, an estimate confirmed by the comparison of values of viscosity of slightly inferior accuracy.     

The thermal conductivity of xylene isomers in the temperature range 290–360 K

New absolute measurements of the thermal conductivity of the three xylene isomers are reported. The measurements have been carried out in the temperature range 290–360 K, at atmospheric pressure, in a transient hot-wire instrument. The accuracy of the measurements is estimated to be ±0.5%. The measurements presented in this paper have been used in conjuction with our earlier reported measurements of liquid benzene and toluene, at atmospheric pressure, to develop a consistent theoretically based predictive scheme for the thermal conductivity of these five aromatic hydrocarbons. The proposed scheme, containing just one parameter characteristic of each fluid, permits the prediction of the thermal conductivity of the five aromatic hydrocarbons in the temperature range 290–360 K and at pressures up to 350 MPa, with an accuracy of ±2.5%.     

The Viscosity and Density of <Emphasis Type="Italic">n</Emphasis>-Dodecane and <Emphasis Type="Italic">n</Emphasis>-Octadecane at Pressures up to 200 MPa and Temperatures up to 473 K

A vibrating-wire instrument for simultaneous measurement of the density and viscosity of liquids under conditions of high pressure is described. The instrument is capable of operation at temperatures between 298.15 and 473.15 K at pressures up to 200 MPa. Calibration was performed by means of measurements in vacuum, air, and toluene at 298.15 K. For n-dodecane measurements were made along eight isotherms between 298.15 and 473.15 K at pressures up to 200 MPa while for n-octadecane measurements were measured along seven isotherms between 323.15 and 473.15 K at pressures up to 90 MPa. The estimated uncertainty of the results is 2% in viscosity and 0.2% in density. Comparisons with literature data are presented.     

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.     

Volume ratios for n-pentane in the temperature range 278–338 K and at pressures up to 280 MPa

Volume ratios (V _P/V _0.1), and isothermal compressibilities calculated from them, are reported for n-pentane for seven temperatures in the range 278 to 338 K for pressures up to 280 MPa. The isobaric measurements were made with a bellows volumometer for which a novel technique had to be devised to enable measurements to be made above the normal boiling point (309.3 K). The accuracy of the volume ratios is estimated to be ±0.05 to 0.1% up to 303.15 K and ±0.1 to 0.2% from 313.15 to 338.15 K. The volume ratios are in good agreement with those calculated from recent literature data up to the maximum pressure of the latter, viz., 60 MPa.     

An automated volumometer: Thermodynamic properties of 1,1-dichloro-2,2,2-trifluoroethane (R123) for temperatures of 278.15 to 338.15 K and pressures of 0.1 to 380 MPa

An automated bellows volumometer is described which is capable of obtaining p-V-T data in the form of volume ratios for pressures up to 380 MPa. Volume ratios for 1,1-dichloro-2,2,2-trifluoroethane (R123) have been measured for six temperatures in the range of 278.15 to 338.15 K in the liquid phase. The accuracy of the volume ratios is estimated to be ±0.05 to 0.1% for the experimental temperatures up to 298.15 K and better than ±0.15% for temperatures above the normal boiling point of R123 (300.15 K). They agree with the literature data (which do not extend beyond 4 MPa) within the experimental uncertainty of those results. Isothermal compressibilities, isobaric expansivities, internal pressures, and isobaric molar heat capacities have been evaluated from the volumetric data. The pressure dependence of isobaric molar heat capacities obtained from the data generally agree with the pressure dependence of experimentally measured literature values within the latter's accuracy of ±0.4%.     

Measurement of Young’s modulus of oxides at high temperature related to the oxidation study

Abstract

α-Al₂O₃, Cr₂O₃, and α-Fe₂O₃ specimens were prepared by a sintering process. A 400 – 1000-Hz sine wave was applied to the specimen at 290 – 1273 K. The applied and respond waves were monitored by using force and acceleration sensors. The intensity ratio and phase shift between the applied and respond waves were analysed, and the anti-resonance frequency was obtained. Young’s moduli of α-Al₂O₃, Cr₂O₃, and α-Fe₂O₃ are estimated to be 386, 286, and 220 GPa at 298 K, respectively. The temperature dependence values of these oxides are estimated to be 54.3, 46.9, and 42.0 MPa K^-1, respectively. The temperature dependence of Young’s modulus can be classified on the basis of the crystal structure of solids. The estimation of Young’s modulus at 1273K is possible with an error range of 10 – 30 GPa for a crystalline solid if the crystal structure of the solid is known. It is found that the temperature dependence of Young’s modulus depends on the density of the oxides, and an experiment in which well-characterized crystalline solids are used must be conducted to minimize the error range.     

Thermal conductivity of water and 2-n-butoxyethanol and their mixtures in the temperature range 305–350 K at pressures up to 150 MPa

The thermal conductivity of binary liquid mixtures of water and 2-n-butoxyethanol has been measured within the temperature range 305–350 K at pressures up to 150 MPa. The measurements have been carried out with a transient hotwire instrument suitable for electrically conducting liquids and have an estimated accuracy of ±0.3%. The liquid mixture has a closed-loop solubility and reveals a lower critical solution temperature for a mole fraction of 2-n-butoxyethanol of 0.0478 at a temperature of 322.25 K. The results of the measurements reveal a small, but discernible, enhancement of the thermal conductivity of the solution at the critical composition.Paper presented at the Twelfth Symposium on Thermophysical Properties. June 19–24, 1994, Boulder, Colorado, U.S.A.     

Thermal conductivity and thermal diffusivity of xylene isomers in the temperature range 308–360 K at pressures up to 0.38 GPa

New, absolute measurements of the thermal conductivity of the three xylene isomers within the temperature range 308–360 K for pressures up to 0.38 GPa are reported. In addition, for two of the isomers, m-xylene and p-xylene, it has been possible to measure the thermal diffusivity simultaneously within the same range of conditions. The accuracy of the thermal conductivity data reported is one of ±0.3%, whereas for the thermal diffusivity the estimated accuracy is ±6%. It is found that the density dependence of the thermal conductivity for all of the xylenes can be well represented by one equation based on a rigid-sphere model in the same way that has proved successful for normal alkanes. The thermal diffusivity data have been employed to derive heat capacities for the xylenes over a range of pressures.     

Viscosity Measurements on Gaseous Argon, Krypton, and Propane1

A new vibrating-wire viscometer was designed to perform quasi-absolute measurements of very high precision on gases. It was applied to determine the viscosity of argon at temperatures of 298.15, 348.15, and 423.15 K and pressures up to 20 MPa, and the viscosity of krypton at 298.15 and 348.15 ,K and pressures up to 16 MPa. Furthermore, several isothermal series of viscosity measurements on gaseous propane were carried out. The subcritical isotherms at 298.15, 323.15, 348.15, and 366.15 K were restricted to 95% of the saturated vapor pressure, the supercritical isotherms at 373.15, 398.15, and 423.15 K to 20 MPa. In general, the measurements are characterized by a reproducibility of ±0.05% and an accuracy of ±0.2%. However, close to the critical point an accuracy of ±3% has to be accepted, mainly due to the uncertainty of the density. In this context the influence of the equation of state used for propane is discussed.     

Thermodynamic and transport properties of 1, 2-dichloroethane

(p, V, T) data for dichloroethane (DCE) have been obtained at 278.15, 288.15, 298.15, 313.15, 323.15, and 338.15 K for pressures either slightly below the freezing pressure or up to a maximum of 280 M Pa, together with densities at 0.1 MPa. A high-pressure self-centering falling-body viscometer method has been used to measure shear viscosities at 278.15, 288.15, 298.15, 313.15, and 323.15 K for pressures either slightly below the freezing pressure or up to a maximum of 330 MPa. Self-diffusion coefficients for DCE are reported at 278.15, 288.15, 298.15, and 313.15 K for maximum pressures up to 300 MPa. Isothermal compressibilities, isobaric expansivities, and internal pressures have been evaluated from the volumetric data. The shear viscosities and self-diffusion coefficients have been interpreted in terms of a modified rough hard-spheres theory. The anomalous behavior observed for p-V-T, shear viscosities, and self diffusion at higher temperatures and pressures is suspected to be the result of temperature and pressure altering the population ratio of the two molecular conformers, trans and gauche.     

Speed-of-Sound Measurements in n-Nonane at Temperatures between 293.15 and 393.15 K and at Pressures up to 100 MPa

Speed-of-sound measurements in liquid phase n-nonane (C₉H₂₀) are reported along six isotherms between 293.15 and 393.15 K and at pressures up to 100 MPa. The experimental technique is based on a double reflector pulse-echo method. The acoustic path lengths were obtained by comparison with measurements carried out at atmospheric pressure and ambient temperature in pure water. The values of the speed of sound are characterized by an overall estimated uncertainty of less than 0.2 %. These results were compared with literature values and with predictions of a dedicated equation of state.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

The viscosity of five liquid hydrocarbons at pressures up to 250 MPa

This paper reports new measurements of the viscosity of toluene, n-pentane, n-hexane, n-octane, and n-decane at pressures up to 250 MPa in the temperature range 303 to 348 K. The measurements were performed with a vibrating-wire viscometer and with a relative method of evaluation. Calibration of the instrument was carried out with respect to reference values of the viscosity of the same liquids at their saturation vapour pressure. The viscosity measurements have a precision of ±0.1% but the accuracy is limited by that of the calibration data to be ±0.5%. The experimental data have been represented by polynomial functions of pressure for the purposes of interpolation. The data are also used as the most precise test yet applied to a representation of the viscosity of liquids based upon hard-sphere theory.     

Viscosity and thermal conductivity of binary n-heptane + n-alkane mixtures

New absolute measurements of the viscosity of binary mixtures of n-heptane with n-hexane and n-nonane are presented. The measurements, performed in a vibrating-wire instrument, cover a temperature range 290–335 K and pressures up to 75 MPa. The concentrations studied are 40 and 70% by weight of n-heptane. The accuracy of the reported viscosity data is estimated to be ±0.5%. The present measurements, together with other n-heptane + n-alkane viscosity and thermal-conductivity measurements, are used to develop a consistent semiempirical scheme for the correlation and prediction of these mixture properties from those of the pure components.     

CO2 + R23 Binary System: Virial Coefficients Derived from Burnett Measurements

Burnett PVT measurements were performed on trifluoromethane (R23) and mixtures of R23 with carbon dioxide (CO₂). The Burnett apparatus was calibrated using helium. Fourteen expansions were performed for 5 isotherms and in a pressure range from 130 kPa to 6 MPa for R23. Second and third virial coefficients were derived from the collected data and compared with literature values; good agreement was found between them. PVTx measurements for the binary CO₂+R23 system were carried out for five isotherms (303, 313, 323, 333, and 343 K). In all, 18 runs were performed in a pressure range from 150 kPa to 5.9 MPa. The composition of the mixtures was measured with a gas chromatograph after it had been calibrated using samples prepared gravimetrically. Second and third virial coefficients for the system were derived, together with the second and third cross virial coefficients, from experimental results using virial coefficients for CO₂ from previous measurements (for the same sample as used in the present study). Samples for composition measurements were collected during the first Burnett expansion. Second virial coefficients for the system showed positive deviations from ideal values, while the third virials were negative. No previous experimental results were found for the PVTx properties of this binary system.     

Volumetric measurements under pressure for 2,2,4-trimethylpentane at temperatures up to 353.15 K and for benzene and three of their mixtures at temperatures up to 348.15 K

(p, V, T) data have been obtained in the form of volume ratios relative to 0.1 MPa for benzene (298.15 to 348.15 K), 2,2,4-trimethylpentane (TMP) (313.15 to 353.15 K), and their mixtures near 0.25, 0.5, and 0.75 mole fraction of benzene (313.15 to 348.15 K) for pressures up to near the freezing pressures for benzene and the mixtures, and up to 400 MPa for TMP. Isothermal compressibilitiesκ _T, isobaric expansivitie α, changes in heat capacity at constant pressureΔC _p, and excess molar volumesV ^E have been determined from the data. Literature data at atmospheric pressure have been used to convert theΔC _p toC _p at several temperatures. The isobars for α over the temperature range 278.15 to 353.15 K for TMP intersect near 47 MPa and reverse their order in temperature when plotted against pressure; normalization of the α's by dividing the values at each temperature by the α at 0.1 MPa prevents both the intersection and the reversal of the order. TheV ^E are positive and have an unusual dependence on pressure: they increase with temperature and pressure so that the order of the curves for 0.1, 50, and 100 MPa changes in going from 313.15 to 348.15 K.