Measurement and correlation of the vapour pressures of 1,1,1,2-tetrafluoroethane (R 134a) and of 1,1-difluoroethane (R 152a)

Abstract

The vapour pressures of the environmentally safe refrigerants 1,1,1,2-tetrafluoroethane (R 134a) and 1,1-difluoroethane (R 152a) were measured. For R 134a, 37 values were obtained for temperatures between 303 K and the critical temperature Tc = 374.18 K. For R 152a, 55 vapour pressures were measured between 301 K and the critical temperature Tc = 386.41 K. The uncertainities of temperature and pressure measurements are estimated to be 5 nK and 0.0001·p, respectively, resulting in a final uncertainty of 0.0002·pσ or less for the vapour pressure pσ. Wagner-type vapour-pressure equations were fitted to the new results and to values from other research groups.