Speed of Sound in Gaseous 1,1-Difluoroethene (R1132a) at Temperatures Between 193 K and 383 K at Pressures up to 3 MPa

Abstract

The speed of sound in gaseous 1,1-difluoroethene (refrigerant R1132a) was measured at temperatures between 193 K and 383 K at pressures up to the lesser of approximately 85 % of the vapour pressure and 3 MPa. The measurements were carried out using a bespoke cylindrical acoustic resonator. The acoustic path length of the resonator was calibrated as a function of temperature by measuring resonance frequencies of the cavity filled with nitrogen gas. The measurements on nitrogen also served to validate the measurement system. The expanded relative uncertainty of the speed of sound in 1,1-difluoroethene at 95% probability was estimated to be 0.021 %. Comparing the results with a preliminary equation of state for 1,1-difluoroethene shows deviations within ± 0.3 %.