(179g) Speed of Sound Measurements of Mixtures of R-1132(E) with R-32 and R-1234yf

Speed of sound measurements performed using a dual-path pulse-echo instrument were preformed up to 8 MPa and temperatures of 344 K. The standard uncertainties in temperature and pressure were 10 mK and 0.014 MPa, respectively. The combined expanded uncertainty in the speed of sound ranged from 0.04% to 0.1% of the measured speed of sound value. Weaker echo signals were encountered as they system approached the critical region resulting in a decreased signal to noise ratio. To maintain a low uncertainty in the speed of sound measurement the number of echoes averaged was increased from a minimum value of 256 to 4096. Upon completion of the measurements the data were compared to the latest empirical mixture models available in REFPROP for both blends. Collectively, the current mixture models deviated from the data as much as 10% at the lowest temperatures and pressures. The data were also compared to the SAFT-VR Mie equation of state, a semi-empirical modeling approach, to quantify the performance of a more predictive method.