Determination of Second Virial Coefficients and Virial Equations of R-32 (Difluoromethane) and R-125 (Pentafluoroethane) Based on Speed-of-Sound Measurements
Source: International Journal of Thermophysics, Volume 20, Number 6, November 1999 , pp. 1677-1688(12)
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 PT data measured by deVries and Tillner-Roth within ±0.01 and ±0.1%, respectively.
Document Type: Research Article
Affiliations: 1: Department of Mechanical Engineering and Science, Faculty of Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan 2: Department of System Design Engineering, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan
Publication date: November 1999