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  • second virial coefficient  (5)
  • PHYSICS, SOLID-STATE  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 587-595 
    ISSN: 1572-9567
    Keywords: alternative refrigerant ; HFC-125 ideal-gas specific heat ; second acoustic-virial coefficient ; second virial coefficient ; sound velocity ; spherical resonator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The sound velocity in gaseous pentafluoroethane (HFC-125, CF3CHF2) has been measured by means of a spherical acoustic resonator, Seventy-two sound-velocity values were measured with an uncertainty of ±0.01% at temperatures from 273 to 343 K and pressures from 101 to 250 kPa. The ideal-gas specific heats and the second acoustic-virial coefficients have been determined on the basis of the Sound-velocity measurements. The second virial coefficients calculated from the present sound-velocity measurements agree with literature values which were determined fromPVT measurements by means of a Burnett method.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 1269-1280 
    ISSN: 1572-9567
    Keywords: alternative refrigerants ; collision integrals ; second virial coefficient ; spherically averaged potential ; viscosite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The second virial coefficients of refrigerants HFC-32 (CH2F2), HFC-23 (CHF3), and HCFC-22 (CHC1F2) have been correlated on the bisis of site site model potential and have been compared with experimental results. The molecular interactions consisted of repulsion dispersion and electrostatic parts. From the site site potentials adjusted to the experimental second virial coefficients, spherically averaged potentials have been determined and a subsequent calculation of gaseous viscosity has been carried out. Agreement between measured and calculated values of second virial coellicients and gaseous viscosity is satisfactory. Calculated values of second virial coefficients and gaseous viscosity beyond available experimental data, therefore. can be assumed as a reliable extrapolation to lower and higher temperatures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 14 (1993), S. 739-762 
    ISSN: 1572-9567
    Keywords: ideal-gas specific heat ; HFC-134a ; HFC-152a ; second acoustic virial coefficient ; second virial coefficient ; spherical resonator ; sound velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A spherical acoustic resonator was developed for measuring sound velocities in the gaseous phase and ideal-gas specific heats for new refrigerants. The radius of the spherical resonator, being about 5 cm, was determined by measuring sound velocities in gaseous argon at temperatures from 273 to 348 K and pressures up to 240 kPa. The measurements of 23 sound velocities in gaseous HFC-134a (1,1,1,2-tetrafluoroethane) at temperatures of 273 and 298 K and pressures from 10 to 250 kPa agree well with the measurements of Goodwin and Moldover. In addition, 92 sound velocities in gaseous HFC-152a (1,1-difluoroethane) with an accuracy of ±0.01% were measured at temperatures from 273 to 348 K and pressures up to 250 kPa. The ideal-gas specific heats as well as the second acoustic virial coefficients have been obtained for both these important alternative refrigerants. The second virial coefficients for HFC-152a derived from the present sound velocity measurements agree extremely well with the reported second virial coefficient values obtained with a Burnett apparatus.
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  • 4
    ISSN: 1572-9567
    Keywords: alternative refrigerant ; equation of state ; hydrofluorocarbon ; R-32 ; R-125 ; second virial coefficient ; speed of sound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The second virial coefficients, B, for difluoromethane (R-32, CH2F2) and pentafluoroethane (R-125, CF3CHF2) are derived from speed-of-sound data measured at temperatures from 273 to 343 K with an experimental uncertainty of ±0.0072%. Equations for the second virial coefficients were established, which are valid in the extensive temperature ranges from 200 to 400 K and from 240 to 440 K for R-32 and R-125, respectively. The equations were compared with theoretically derived second virial coefficient values by Yokozeki. A truncated virial equation of state was developed using the determined equation for the virial coefficients. The virial equation of state represents our speed-of-sound data and most of the vapor PρT data measured by deVries and Tillner-Roth within ±0.01 and ±0.1%, respectively.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 8 (1987), S. 217-229 
    ISSN: 1572-9567
    Keywords: bromotrifluoromethane ; compression factor ; second virial coefficient ; vapor pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The compression factors and vapor pressures have been measured on bromotrifluoromethane using a Burnett apparatus. The results on the compression factor cover the range of temperatures 263 to 393 K and of pressures 0.14 to 11.6 MPa, corresponding to a density variation from 7 to 1367 kg· m−3. The experimental uncertainty of these 176 measurements of compression factor was estimated to be 0.2%. Thirty measurements of vapor pressure were made for temperatures 245 to 339 K, with an experimental uncertainty of 0.1%. Based on these results, the second virial coefficients were determined for temperatures 293 to 393 K.
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  • 6
    Publication Date: 2019-05-29
    Description: Intensity measurements in vacuum ultraviolet - photoelectric yields of untreated metals and semiconductors measured by calibrated thermocouple
    Keywords: PHYSICS, SOLID-STATE
    Type: NASA-CR-58429
    Format: application/pdf
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  • 7
    Publication Date: 2019-05-29
    Description: Electron emission, conductivity, and luminescence of selected solids under ultraviolet radiation
    Keywords: PHYSICS, SOLID-STATE
    Type: NASA-CR-75109
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  • 8
    Publication Date: 2019-06-27
    Description: Photoelectric emission measurements of excited electrons attenuation length in metal films as function of film thickness
    Keywords: PHYSICS, SOLID-STATE
    Type: NASA-CR-90062
    Format: text
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