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  • Computational Chemistry and Molecular Modeling  (31)
  • thermal conductivity  (23)
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  • 1
    Electronic Resource
    Electronic Resource
    Status of the round robin on the transport properties of R134a (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 63-78 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01438958
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  • 2
    Electronic Resource
    Electronic Resource
    Radiative heat transfer in transient hot-wire measurements of thermal conductivity (1991)
    Springer
    International journal of thermophysics 12 (1991), S. 985-997 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00503514
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal conductivity surface of argon: A fresh analysis (1991)
    Springer
    International journal of thermophysics 12 (1991), S. 965-984 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00503513
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  • 4
    Electronic Resource
    Electronic Resource
    The thermal conductivity of 1-chloro-1,1-difluoroethane (HCFC-142b) (1992)
    Springer
    International journal of thermophysics 13 (1992), S. 383-399 
    Details
    ISSN: 1572-9567
    Keywords: concentric cylinder apparatus ; 1-chloro-1,1-difluoroethane ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of 1-chloro-1,1-difluoroethane (HCFC-142b) has been measured in the temperature range 290 to 504 K and pressures up to 20 MPa with a concentric-cylinder apparatus operating in a steady-state mode. These temperature and pressure ranges cover all fluid states. The estimated accuracy of the method is about 2%. The density dependence of the thermal conductivity has been studied in the liquid region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503878
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal Conductivity of 1,1-Difluoroethane (HFC-152a) (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 63-72 
    Details
    ISSN: 1572-9567
    Keywords: 1,1-difluoroethane ; HFC 152a ; liquid ; modified van der Waals model ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thermal conductivity measurements were performed on 1,1-difluoroethane (HFC-152a) using the polarized transient hot-wire technique in the temperature range of 214 to 294 K and at pressures up to 19 MPa. This technique was used previously for measurements on other halocarbons along the saturation line and in the compressed liquid phase. No dependence of the polarization voltage was found for the thermal conductivity values, demonstrating that the technique was used with success. Also, no influence of heat transfer by radiation or convection was detected, in all the range of densities studied. The samples were supplied with stated purities greater than 99.9%. The reproducibility of the experiments was found to be 0.03%, while the total uncertainty is estimated to be 0.5%. The experimental data were compared with data from other sources. Values for the thermal conductivity along the saturation line for several temperatures were achieved by extrapolating the high-pressure data to the saturation density for each isotherm. The data obtained were also correlated using a modification of the van der Waals model (smooth hard spheres) with an uncertainty of 1.1%, at a 95% confidence level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021422012447
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  • 6
    Electronic Resource
    Electronic Resource
    A computer-controlled instrument for the measurement of the thermal conductivity of liquids (1987)
    Springer
    International journal of thermophysics 8 (1987), S. 511-519 
    Details
    ISSN: 1572-9567
    Keywords: liquids ; measurement technique ; thermal conductivity ; toluene ; transient hot-wire method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new instrument for the measurement of the thermal conductivity of liquids by the transient hot-wire method is described. The instrument has features in common with earlier versions but employs a novel technique for the determination of the transient temperature rise of the hot wire during the course of a measurement. New determinations of the thermal conductivity of toluene confirm the accuracy of the instrument to be better than 0.5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503639
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal diffusivity measurement by the transient hot-wire technique: A reappraisal (1988)
    Springer
    International journal of thermophysics 9 (1988), S. 293-316 
    Details
    ISSN: 1572-9567
    Keywords: argon ; thermal conductivity ; thermal diffusivity ; toluene ; transient hot-wire technique ; m-xylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The theory of the transient hot-wire technique for thermal conductivity measurements is reassessed in the special context of thermal diffusivity measurements. A careful examination of the working equation and an error analysis are employed to identify the principal sources of error. Notwithstanding earlier claims to the contrary, the best precision that can be attained in thermal diffusivity measurements is of the order of ±3%, while the accuracy is inevitably poorer. Experimental evidence is adduced from two different instruments that supports the analysis given here. Although the technique cannot yield values of the thermal diffusivity, k, as accurate as can be achieved by the use of the best possible individual values of λ,ρ, and C p in the relation k=λ/ρC p, the simplicity of the technique makes it attractive for many purposes. It is even possible to derive values of the isobaric heat capacity C p for many fluids not available from other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00513073
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  • 8
    Electronic Resource
    Electronic Resource
    The thermal conductivity of benzene and toluene (1989)
    Springer
    International journal of thermophysics 10 (1989), S. 1005-1011 
    Details
    ISSN: 1572-9567
    Keywords: benzene ; thermal conductivity ; toluene ; transient hot-wire method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of liquid toluene and benzene was measured in the temperature range 298 to 370 K, near the saturation line, using an absolute transient hot-wire technique. The measurements were made in a modified version of an existing instrument, equipped with a new automatic Wheatstone bridge, computer controlled. The bridge measures the time that the resistance of a 7-μm-diameter platinum wire takes to reach predetermined values, programmed by the computer. The computer can generate up to 1024 analog voltages, via a 12-bit D/A converter. The accuracy of the measurements with this new arrangement was assessed by measuring the thermal conductivity of a primary standard, toluene, at several temperatures and was found to be of the order of 0.3%. Benzene was chosen because it is under study as a possible secondary standard for liquid thermal conductivity by the Subcommittee on Transport Properties of IUPAC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503169
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  • 9
    Electronic Resource
    Electronic Resource
    The thermal conductivity of liquid argon for temperatures between 110 and 140 K with pressures to 70 MPa (1987)
    Springer
    International journal of thermophysics 8 (1987), S. 521-540 
    Details
    ISSN: 1572-9567
    Keywords: argon (liquid) ; high pressures ; low temperatures ; thermal conductivity ; transient hot-wire method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503640
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal conductivity of argon in the temperature range 107 to 423 K (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 259-272 
    Details
    ISSN: 1572-9567
    Keywords: argon ; 0hard-sphere theory ; modified Enskog theory ; thermal conductivity ; transient hot-wire technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of argon between 107 and 425 K has been measured in a transient hot-wire instrument. The results in the limit zero density have been employed to assess the accuracy of the instrument using exact kinetic theory expressions and has been found to be better than ±0.5%. The data at elevated densities are employed to examine the applicability of the modified Enskog theory in the gaseous phase and the hard-sphere theory in the liquid phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500153
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