Isochoric p-rho-T and heat capacity C-v measurements for ternary refrigerant mixtures containing difluoromethane (R32), pentafluoroethane (R125), and1,1,1,2-tetrafluoroethane (R134a) from 200 to 400 K at pressures to 35 MPa

The p p T relationships and constant volume heat capacity C-v were measured for ternary refrigerant mixtures by isochoric methods with gravimetric det erminations of the amount of substance. Temperatures ranged from 200 to 400 K for p p T and from 203 to 345 K for C-v, while Fur both data types press ures extended to 35 MPa. Measurements of p-p-T were carried out on compress ed gas and liquid samples with the following mole fraction compositions: 0. 3337 R32+0.3333 R125+0.3330 R134a and 0.3808 R32+0.1798 R125+0.4394 R134a. Measurements of C-v were carried out on liquid samples for the same tale co mpositions. Published p p-T data are in good agreement with this study for the p p-T apparatus, the uncertainty is 0.03 K for temperature and is 0.01 % for pressure at p > 3 M Pa and 0.05 % at p < 3 M Pa. The principal source of uncertainty is the cell volume ( similar to 28.5 cm(3)), with a standar d uncertainty of 0.003 cm(3). When all components of experimental uncertain ty are considered, the expanded relative uncertainty (with a coverage facto r k=2 and, thus, a two-standard deviation estimate) of the density measurem ents is estimated to be 0.05 %. For the C-v calorimeter, the uncertainty of the temperature rise is 0.002 K and For the change-of-volume work it is 0. 2%; the latter is the principal source of uncertainty. When all components of experimental uncertainty are considered, thr expanded relative uncertain ty of the heat capacity measurements is estimated to be 0.7%.