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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 1 (1980), S. 243-284 
    ISSN: 1572-9567
    Keywords: diffusion coefficient ; liquid mixtures ; Taylor dispersion ; liquid diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper presents a complete analysis of the theory of an instrument to measure the diffusion coefficients in liquid mixtures based upon the phenomenon of Taylor dispersion. The analysis demonstrates that it is possible to design an instrument that operates very nearly in accordance with the simplest mathematical description of the dispersion of a solute pulse in a fluid in laminar flow within a straight, circular cross-section tube. The small departures of a practical instrument from the ideal are evaluated as corrections by means of a general perturbation treatment that allows them to be examined one at a time. The corrections considered include the effects of the finite volume of the injection pulse, the finite volume of the concentration monitor, the coiling of the tube, and the nonuniformity and noncircularity of the cross section, as well as the variation of the fluid properties with composition. All the equations necessary for the design of an instrument of this type, and for the evaluation of experimental data free from significant systematic errors, are presented.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 12 (1991), S. 985-997 
    ISSN: 1572-9567
    Keywords: radiative heat transfer ; thermal conductivity ; toluene ; transient hot-wire technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New measurements of the thermal conductivity of liquid toluene between 300 and 550 K have been used to study the importance of radiative heat transfer when using the transient hot-wire technique. The experimental data were used to obtain the radiation correction to the hot-wire temperature rises. Radiationcorrected values of thermal conductivity are reported. This study shows that the transient hot-wire method is much less affected by radiation than steady-state techniques.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 16 (1995), S. 63-78 
    ISSN: 1572-9567
    Keywords: R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The paper contains a status report on an international project coordinated by the Subcommittee on Transport Properties of Commission 1.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the sample. This paper provides an intercomparison of the new experimental results obtained to data in this project for the viscosity and the thermal conductivity in both gaseous and liquid phases. The agreement between the viscosity data from the laboratories contributing to the project was improved with several techniques, now producing consistent results. This suggests that the purity of the samples of R134a used in previous work was at least partly reponsible for the discrepancies observed. For the thermal conductivity in the liquid phase the results of the measurements are also more consistent than before, although not for all experimental techniques. Not all of the previous measurements suffered from significant sample impurities, so the present measurements on a consistent high-purity sample can he used to detect data sets which are outhers, possibly because of impurities. Identification of laboratories and techniques with systematic differences may require the examination of data for several fluids. The implications for future measurements of the transport properties of other refrigerants are significant.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 551-560 
    ISSN: 1572-9567
    Keywords: density ; HCFC 141b ; pressure ; temperature ; Tait equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The density of HCFC 141b has been measured at several temperatures between 260 and 320 K, Mid pressures up to 20 MPa, with a mechanical oscillator densimeter. The densimeter was calibrated with 2,2,4-trimethylpentane, whose density was obtained from a correlating cyuation with 0.3% uncertainty. The density data obtained for HCFC 14H) hits a reproducibility of 0.05% and an uncertainty of 0.3%. The data obtained were fitted to a Tait-type equation. which reproduced the experimental densities within 0.11 % and were compared with the data obtained in other works.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 573-585 
    ISSN: 1572-9567
    Keywords: density ; dielectric constant ; dipole moment ; HFC 134a ; HCFC 142b ; Kirkwood equation ; refrigerant ; Vedam equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper presents measurements of the dielectric constant of HFC 134a and HCFC 1426, as a function of pressure and temperature, in the temperature range from 200 to 300 K and pressures up to 20 M Pa, using a direct capacitance method, The samples used had a stated purity of 99.8 and 99.9%, respectively, The values of the dielectric constant have a precision of 0.01 % and an accuracy of 0.1%, The data obtained were correlated as a function of density and pressure, The theory developed by Vedam et al,, based on the Eulerian strain. and the Kirkwood equation for the variation of modified molar polarization with temperature and density were applied to analyze the data and to obtain the dipole moment of both refrigerants in the liquid state.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 4 (1983), S. 11-33 
    ISSN: 1572-9567
    Keywords: butane ; corresponding states ; critical region ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of n-butane has been measured by a coaxial-cylinder method over a pressure range from 0.1 MPa up to 70 MPa and a temperature range from room temperature to 600 K, covering all fluid states. The estimated accuracy of the method is about 2%. Special emphasis has been given to the behavior of the thermal conductivity near the critical point, and the critical enhancement has been studied for 3.6 K〈δT〈176 K. The effect of inelastic collisions upon transport properties of the dilute gas has been discussed. The results obtained for the reduced critical enhancement as a function of the reduced critical temperature confirm the universality of the critical exponent, for the n-alkanes, whereas the reduced excess thermal conductivity outside the critical region is a function of the reduced density and of the n-alkane.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 9 (1988), S. 351-363 
    ISSN: 1572-9567
    Keywords: correlation ; n-alkanes ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of liquids has been shown in the past to be difficult to predict with a reasonable accuracy, due to the lack of accurate experimental data and reliable prediction schemes. However, data of a high accuracy, and covering wide density ranges, obtained recently in laboratories in Boulder, Lisbon, and London with the transient hot-wire technique, can be used to revise an existing correlation scheme and to develop a new universal predictive technique for the thermal conductivity of liquid normal alkanes. The proposed correlation scheme is constructed on a theoretically based treatment of the van der Waals model of a liquid, which permits the prediction of the density dependence and the thermal conductivity of liquid n-alkanes, methane to tridecane, for temperatures between 110 and 370 K and pressures up to 0.6 MPa, i.e., for 0.3⩽T/T c⩽0.7 and 2.4⩽P/P c⩽3.7, with an accuracy of ±1%, given a known value of the thermal conductivity of the fluid at the desired temperature. A generalization of the hard-core volumes obtained, as a function of the number of carbon atoms, showed that it was possible to predict the thermal conductivity of pentane to tetradecane±2%, without the necessity of available experimental measurements.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 12 (1991), S. 965-984 
    ISSN: 1572-9567
    Keywords: argon ; liquid ; supercritical ; surface fit ; thermal conductivity ; transient hot wire technique ; vapor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper presents a fresh analysis of the thermal conductivity surface of argon at temperatures between 100 and 325 K with pressures up to 70 MPa. The new analysis is justified for several reasons. First, we discovered an error in the compression-work correction, which is applied when calculating thermal conductivity and thermal diffusivity obtained with the transient hot-wire technique. The effect of the error is limited to low densities, i.e., for argon below 5 mol·L−1. The error in question centers on the volume of fluid exposed to compression work. Once corrected, the low-density data agree very well with the available theory for both dilute-gas thermal conductivity and the first density coefficient of thermal conductivity. Further, the corrected low-density data, if used in conjunction with our previously reported data for the liquid and supercritical dense-gas phases, allow us to represent the thermal conductivity in the critical region with a recently developed mode-coupling theory. Thus the new surface incorporates theoretically based expressions for the dilute-gas thermal conductivity, the first density coefficient, and the critical enhancement. The new surface exhibits a significant reduction in overall error compared to our previous surface which was entirely empirical. The uncertainty in the new thermal conductivity surface is ±2.2% at the 95% confidence level.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 21 (2000), S. 415-427 
    ISSN: 1572-9567
    Keywords: azeotropic mixture ; density ; dielectric constant ; Kirkwood equation ; pressure ; R410A ; relative permittivity ; Vedam equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The purpose of this paper is to present dielectric constant measurements of R410A, a chlorine-free refrigerant, which is a 50/50 (mass %) mixture of R32/125. The measurements on R410A were performed as a function of pressure and temperature ranging from 2 to 16 MPa and from 217 to 304 K, respectively, by using a direct capacitance method. The values of dielectric constant have an estimated repeatability of ±0.01% and an accuracy of ±0.1%. The data were correlated as a function of density and pressure. The theory developed by Vedam et al., and adapted by Diguet, and the Kirkwood modification of the Onsager equation for the variation of the modified molar polarization with temperature and density were applied to analyze the data and to obtain the dipole moment of R410A in the liquid state. This was found to be 3.31 Debye.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 21 (2000), S. 639-650 
    ISSN: 1572-9567
    Keywords: empirical correlation ; n-alkane ; propane ; thermal conductivity ; transport properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New experimental data on the thermal conductivity of propane have been reported since the wide-range correlations proposed by Holland et al. and by Younglove and Ely. These new experimental data, covering a temperature range of 110 to 700 K and a pressure range of 0.1 to 70 MPa, are used together with the previously available data to develop an improved empirical equation for the thermal conductivity of gaseous and liquid propane. The quality of the new data is such that the thermal-conductivity correlation for propane is estimated to have an uncertainty of about ±5% at a 95% confidence level, with the exception of state points near the critical point, where the uncertainty of the correlation increases to ±10%.
    Type of Medium: Electronic Resource
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