Density and speed of sound in refrigerant vapor R-125 (31 wt. %) + R-134A (69 wt. %)

Using a constant volume piezometer and ultrasonic interferometer methods, the density and speed of sound in gaseous mixture R-125 (31 wt. %) + R-134a (69 wt. %) were measured within the temperature range from 293 to 393 K and at pressure from 0.18…0.47 to 2.5 MPa. The errors in the measuring temperature, pressure, density and speed of sound were ±20 mK, ±4 kPa, ± (0.15–0.3) %, ± (0.1–0.2) %, respectively. It was shown that the speed of sound values increase with temperature and decrease with pressure. The obtained results were compared with the calculations using the REFPROP software.