Determination of Second Virial Coefficients and Virial Equations of R-32 (Difluoromethane) and R-125 (Pentafluoroethane) Based on Speed-of-Sound Measurements
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.
- Publication:
-
International Journal of Thermophysics
- Pub Date:
- November 1999
- DOI:
- 10.1023/A:1022601811779
- Bibcode:
- 1999IJT....20.1677H
- Keywords:
-
- alternative refrigerant;
- equation of state;
- hydrofluorocarbon;
- R-32;
- R-125;
- second virial coefficient;
- speed of sound