EQUATION OF STATE AND IDEAL-GAS HEAT-CAPACITY OF A GASEOUS MIXTURE OF1,1,1,2-TETRAFLUOROETHANE, PENTAFLUOROETHANE, AND DIFLUOROMETHANE

We present the gas-phase equation of state and ideal-gas heat capacity of a ternary mixture (nominal molar concentration) of 1,1,1,2-tetrafl uoroethane (35%), pentafluoroethane (30%), and difluoromethane (35%) f or temperatures between 260 and 453 K and pressures between 0.05 and 7 .7 MPa. These results were based on two very different measurement tec hniques. The first technique measured the gas density of the mixture i n a Burnett apparatus from 313 to 453 K and From 0.2 to 7.7 MPa. The s econd technique deduced the gas density and ideal-gas heat capacity fr om high-accuracy speed-of-sound measurements in the mixture at tempera tures between 260 and 400 K and at pressures between 0.05 and 1.0 MPa, The data from the two techniques were analyzed together to obtain an equation of state that reproduced the densities From the Burnett techn ique with a fractional RMS deviation of 0.038%, and it also reproduced the sound speeds with a Fractional RMS deviation of 0.003%. Finally, the results are compared Co a predictive model based on the properties of the pure fluids.