Saturated Liquid Viscosity and Surface Tension of Alternative Refrigerants

Light scattering by thermally excited capillary waves on liquid surfaces or iInter- faces can be used for the investigation of viscoelastic properties of fluids. In this work, we carried out the simultaneous determination of the surface tension and the liquid kinematic viscosity of some alternative refrigerants by surface light scattering (SLS) on a gas liquid iInterface. The experiments are based on a hetero- dyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). R23 (trifluoromethane), R32 (difluoromethane), R125 (pentafluoro- ethane), R143a (1,1,1-trifluoroethane), R134a (1,1,1,2-tetrafluoroethane), R152a (1,1-difluoroethane), and R123 (2,2-dichloro-1,1,1-trifluoroethane) were investi- gated under saturation conditions over a wide temperature range, from 233 K up to the critical point. It is estimated that the uncertainty of the present surface tension data for the whole temperature range is less than \0.2 mN } m&1. For temperatures up to about 0.95Tc , the kinematic viscosity of the liquid phase could be obtained with an absolute accuracy of better than 20. For the highest temperatures studied in this work, measurements for the kinematic viscosity exhibit a maximum uncertainty of about \40. Viscosity and surface tension data are represeInted by a polynomial function of temperature and by a van der Waals-type surface tension equation, respectively. The results are discussed in detail with comparison to literature data.