Measurements of the viscosity of n-heptane + n-undecane mixtures at pressures up to 75 MPa

New absolute measurements of the viscosity of binary mixtures of n-heptane and n-undecane are presented. The measurements, performed in a vibrating-wire instrument, cover the temperature range 295–335 K and pressures up to 75 MPa. The concentrations studied were 40 and 70%, by weight, of n-heptane. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to predict successfully both the thermal conductivity and the viscosity of these mixtures, as a function of composition, temperature, and pressure.     

Thermal Conductivity and Viscosity of Aqueous K<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript>SO<Subscript><Emphasis Type="Bold">4</Emphasis></Subscript> Solutions at Temperatures from 298 to 575 K and at Pressures up to 30 MPa

The thermal conductivity of three (0.239, 0.499, and 0.782 mol·kg⁻¹) and the viscosity of four (0.0658, 0.2055, 0.3050, and 0.4070 mol·kg⁻¹) binary aqueous K₂SO₄ solutions have been measured with coaxial-cylinder (steady-state) and capillary-flow techniques, respectively. Measurements were made at pressures up to 30 MPa, and the range of temperature was 298–575 K. The total uncertainties of the thermal conductivity, viscosity, pressure, temperature, and composition measurements were estimated to be less than 2%, 1.6%, 0.05%, 30 mK, and 0.02%, respectively. The measured values of the thermal conductivity and viscosity of K₂SO₄ (aq) were compared with data and correlations reported in the literature. The reliability and accuracy of the experimental method was confirmed with measurements on pure water with well known (IAPWS standards) thermal conductivity and viscosity values (deviations, AAD, within 0.31 % and 0.52 %, respectively). The values of the viscosity A-, B-, and D-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η₀) of aqueous K₂SO₄ solutions as a function of temperature were studied. The maximum of the B-coefficient near 340 K has been found. The derived values of the viscosity A- and B-coefficients were compared with results predicted by the Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data. The behavior of the concentration dependence of the relative viscosity of aqueous K₂SO₄ solutions is discussed in terms of the modern theory of transport phenomena in electrolyte solutions.     

Magnetic field orientation dependence of critical current in industrial Nb3Sn strands

In usual superconducting devices such as magnets for NMR, the magnetic field is perpendicular to the superconducting strand axis. But in some special devices, such as magnets for the toroidal field system of fusion machines, the strands can experience any field orientation. For NbTi strands, the pinning force is dependent on the field orientation because of the drawing process (Takacs, S., Polak, M. and Krempasky, L., Critical currents of NbTi tapes with differently oriented anisotropic defects, Cryogenics, 1983, 23, 153–159). In the case of Nb₃Sn strands, the draw and react process suggests that the pinning force is isotropic. In fact, preliminary experiments have shown the contrary, which is why the magnetic field orientation dependence of the critical current for two types of industrial Nb₃Sn strands has been measured. These measurements have been performed for seven field orientations at field strengths up to 20 T. A clear anisotropic effect has been observed, which cannot be explained by Kramer's pinning law. The results are in very good agreement with an empirical law proposed in a recent study by Takayasu et al. (Takayasu, M., Montgomery, D.B. and Minervini, J.V., Effect of magnetic field direction on the critical current of twisted multifilamentary superconducting wires, Inst. of Phys. Conf. Ser., 1997, 158, 917–920). The parameters to be used in this law could be specific to the manufacturing process.     

Viscosity of diallyl ether within the temperature range 291.7–626.6 K and within the pressure range 0.101–58.86 MPa

Results of an experimental investigation of the dynamic viscosity of liquid diallyl ether within the temperature range 291.7–525.6 K and pressure range 0.101–58.86 MPa are presented along with equations describing the relationship between the dynamic viscosity and the density of the substance at various temperatures and pressures.K. Dzhuraev State Pedagogical University, Dushanbe, Tadjikistan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 619–621, July–August 1995.     

Temperature dependence of dynamic Young's modulus and internal friction in LPPS NiCrAlY

The piezoelectric ultrasonic composite oscillator technique (PUCOT), operating near 80 kHz, was used to measure the temperature dependence, in the range 23–1000 °C, of dynamic Young's modulus,E, and internal friction,Q ^–1 in three compositions of low-pressure plasma-sprayed NiCrAlY: Ni-15.6Cr-5.2Al-0.20Y (16-5), Ni-17.2Cr-11.6Al-0.98Y (17–12), and Ni-33Cr-6.2 Al-0.95 Y (33–6). Ambient temperature (23 °C) dynamic Young's moduli for the three alloys were 205.0, 199.8, and 231.0 GPa, respectively. In each case, dE/dT was found to be — 0.06 GPa °C^–1 over temperature ranges 23–800, 23–400 and 600–900, and 23–700 °C, respectively. Internal friction was essentially independent of temperature to about 600 °C (700 °C for the 16–5 alloy), at which point a temperature dependence of the formQ ^–1 =A exp (C/RT) was observed. The constantA for the three alloys was determined to be 62.7, 555, and 2.01 × 10⁶, respectively. The constantC for the three alloys was determined to be 82.8, 111, and 170 kJ/mol^–1, respectively. While the physical mechanism is not fully understood, both the pre-exponential constantA and the activation energyC correlate with durability in thermal barrier coatings (TBCs) wherein these alloys are used as bond coats.     

Reference Correlation for the Viscosity of Liquid Toluene from 213 to 373 K at Pressures to 250 MPa

A correlation in terms of temperature and molar volume is recommended for the viscosity of liquid toluene as a reference for high-pressure viscosity measurements. The temperature range covered is from 213 to 373 K, and the pressure range from atmospheric up to 250 MPa. The standard deviation of the proposed correlation is 1.36%, and, within a 95% confidence limit, the error is 2.7%. It is estimated that for densities up to 920 kg·m^–3the uncertainty of the viscosity values generated by this correlation is about ±2%.     

Viscosity and Density of Methane+cis-Decalin from 323 to 423 K at Pressures to 140 MPa

Dynamic viscosity () and density () data are reported for methane+cis-decahydronaphthaline (decalin) binary mixtures of 25, 50, and 75 mass% (74, 90, and 96 mol%) methane at three temperatures (323, 373, and 423 K) from saturation pressure to 140 MPa. A capillary tube viscometer was used for measuring the dynamic viscosity, with the density being calculated from measurements of sample mass and volume. The overall uncertainties in the reported data are 1.0 and 0.5% for the viscosity and density measurements, respectively.     

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.     

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.     

Measurements of the viscosity of toluene + mesitylene mixtures at pressures up to 55 MPa

New absolute measurements of the viscosity of mesitylene and binary mixtures of toluene + mesitylene are presented. The measurements were performed in a vibrating-wire instrument and cover a temperature range of 295–330 K and pressures up to 55 MPa. The concentrations studied were 40 and 70%, by weight, of toluene. The overall uncertainty in the reported data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the viscosity of mixtures from the pure components is used to predict successfully the viscosity of these mixtures, as a function of composition, temperature, and pressure.     

Peak and recovery heat flux densities in bath of subcooled superfluid helium

This paper describes the measurement of the peak and recovery heat flux densities (q_P, q_R) in a bath of subcooled superfluid helium. A RhFe wire (d = 51 μm, L = 34.8 mm) was horizontally immersed in a He Ilp cryostat, which served as the sample, the heater and the temperature sensor. For the steady state measurement a programmed voltage method with a triangular waveform of 20 s was applied. The measured q_P and q_R values cover the temperature range 1.81–2.1K at a pressure of 0.1 MPa. On the basis of the heat and mass transfer through phase interfaces, theoretical relations (without geometrical parameters) of q_P and q_R are derived, which have very wide application range due to the relative critical heat flux density method used for the calculations. The theoretical results fit the experimental results well for both q_P and q_R.     

Thermal properties of superheated potassium vapor at temperatures up to 2150 k and pressures up to 10 MPa

Based on experimental data on thermalproperties, we have constructed tables of thermodynamic fonctions for superheated potassium vapor, and these include the values of the specific volume v, enthalpy h, entropy s, isobaric C _p and isochronous C _v heat capacities, speed of sound A, coefficient of compressibility Z, and they encompass areas of parameters related to pressure P=0.1–10.0 MPa and temperature T=1075–2150 K.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 3, pp. 467–473, March, 1991.     

Thermal conductivity of gaseous fluorocarbon refrigerants R 12, R 13, R 22, and R 23, under pressure

The thermal conductivity of four gaseous fluorocarbon refrigerants has been measured by a vertical coaxial cylinder apparatus on a relative basis. The fluorocarbon refrigerants used and the ranges of temperature and pressure covered are as follows: R 12 (Dichlorodifluoromethane CCl₂F₂): 298.15–393.15 K, 0.1–4.28 MPa R 13 (Chlorotrifluoromethane CClF₃): 283.15–373.15 K, 0.1–6.96 MPa R 22 (Chlorodifluoromethane CHClF₂): 298.15–393.15 K, 0.1–5.76 MPa R 23 (Trifluoromethane CHF₃): 283.15–373.15 K, 0.1–6.96 MPaThe apparatus was calibrated using Ar, N₂, and CO₂ as the standard gases. The uncertainty of the experimental data is estimated to be within 2%, except in the critical region. The behavior of the thermal conductivity for these fluorocarbons is quite similar; thermal conductivity increases with increasing pressure. The temperature coefficient of thermal conductivity at constant pressure, (/T) _p , is positive at low pressures and becomes negative at high pressures. Therefore, the thermal conductivity isotherms of each refrigerant intersect each other in a specific range of pressure. A steep enhancement of thermal conductivity is observed near the critical point. The experimental results are statistically analyzed and the thermal conductivities are expressed as functions of temperature and pressure and of temperature and density.     

Dynamic viscosity of aqueous solutions of hydrazine with high state parameters

We report the results of measurements of the dynamic viscosity of aqueous solutions of hydrazine with a molar concentration of water ranging from 10 to 90%, in the temperature interval 293–558.4 K and the pressure interval 0.101–58.86 MPa.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 43–45, September, 1994.     

Electrical resistivity and thermoelectric power of polycrystalline and amorphous Se-Te-Cu system

The dark electrical resistivity and thermoelectric power have been measured for the bulk ternary alloy Se-Te-Cu. The samples were both polycrystalline and amorphous in structure. The measurements were carried out below room temperature. Depending on Cu addition, crystallographic structure, and amorphous or polycrystalline state, the samples manifested semiconducting or metallic behaviour. The maximum difference in electrical resistivity magnitude was of 14 orders. The activation energy ΔE of charge carriers determined for all semiconducting samples ranged from 0.07 to 0.25 eV. An increase in thermoelectric power resulting from the electron–phonon mass enhancement was estimated.     

Kapitza resistance and thermal conductivity of Kapton in superfluid helium

We have determined simultaneously the Kapitza resistance, R_K, and the thermal conductivity, κ, of Kapton HN sheets at superfluid helium temperature in the range of 1.4–2.0 K. Five sheets of Kapton with varying thickness from 14 to 130 μm, have been tested. Steady-state measurement of the temperature difference across each sheet as a function of heat flux is achieved. For small temperature difference (10–30 mK) and heat flux density smaller than 30 W m⁻², the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. Our method determines with good accuracy the Kapitza resistance, R_K=(10540±444)T⁻³×10⁻⁶ K m² W⁻¹, and the thermal conductivity, κ=[(2.28±0.54)+(2.40±0.32)×T]×10⁻³ W m⁻¹ K⁻¹. Result obtained for the thermal conductivity is in good agreement with data found in literature and the Kapitza resistance’s evolution with temperature follows the theoretical cubic law.     

The thermal conductivity and viscosity of benzene

New absolute measurements of the thermal conductivity of liquid benzene are reported. The measurements have been carried out in the temperature range 295–340 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 conjunction with other high-pressure measurements of thermal conductivity and viscosity, to develop a consistent theoretically based correlation for the prediction of these properties. The proposed scheme permits the density dependence of the thermal conductivity and viscosity of benzene, for temperatures between 295 and 375 K and pressures up to 400 MPa, to be represented successfully by two equations containing just two parameters characteristic of the fluid at each temperature.     

High-Pressure Viscosity and Density Behavior of Ternary Mixtures: 1-Methylnaphthalene+n-Tridecane+2,2,4,4,6,8,8-Heptamethylnonane

The dynamic viscosity and the density of the ternary system, n-tridecane+1-methylnaphthalene+2,2,4,4,6,8,8-heptamethylnonane, were measured as a function of temperature from 293.15 to 353.15 K in 10 K increments at pressures up to 100 MPa. A falling body viscometer was used for measuring the dynamic viscosity above 0.1 MPa, while at 0.1 MPa the viscosity was obtained with an Ubbelohde viscometer. The overall uncertainty in the reported data is less than 1 kg·m^–3 for densities and 2% for viscosities, except at 0.1 MPa where the uncertainty is less than 1%. The experimental results correspond to 882 values of viscosity. With reference to the 126 values published previously for the pure compounds and 882 values for the three associated binaries, the system is globally described by 1890 experimental values as a function of pressure, temperature, and composition. The results for the viscosity are discussed in terms of mixing laws and the excess activation energy of viscous flow.     

Shear viscosity coefficients of compressed gaseous and liquid carbon dioxide at temperatures between 220 and 320 K and at pressures to 30 MPa

The shear viscosity coefficients of compressed gaseous and liquid carbon dioxide hav been measured with the torsional piezoelectric crystal method at temperatures between 220 and 320 K and at pressures to 30 MPa. The dependencies of the viscosity on pressure, density, and temperature and the dependencies of the fluidity (inverse viscosity) on molar volume and temperature have been examined. The measurements on the compressed liquid were correlated with a modified Hildebrand equation.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.