An 18-coefficient, modified Benedict-Webb-Rubin equation of state for R134a (1,1,1,2-tetrafluoroethane) has been developed. New correlations of vapour pressure and saturated liquid density are presented. The temperature scale is given in the new International Temperature Scale of 1990 (ITS-90). This equation of state has been developed based on the experimental data of PVT properties, saturation properties, and isochoric heat capacities by using a least-squares fitting. The experimental data of isobaric heat capacities, speed of sound, and second virial coefficients were also taken into consideration as secondary data. This equation of state is effective both in the super-heated gaseous phase and the compressed liquid phase at pressures up to 70 Mpa, densities to 1,600 kg/m3, and temperatures from 180 K to 500 K.

KEYWORDS: refrigerants, R134a, vapour pressure, liquids, density, temperature, thermodynamics, properties