Experimental measurements and molecular simulations for pvTz properties of carbon dioxide (CO2) + 1,1-difluoroethylene (R1132a) binary system in the two-phase and superheated vapor regions

This study provides 23 two-phase and 133 vapor-phase pressure-specific volume-temperature-composition ( pvTz ) measurements for the mixture containing carbon dioxide (CO 2 ) and 1,1-difluoroethylene (R1132a), considered a potentially low global warming potential (GWP) alternative for ultralow temperature refrigeration systems. Vapor-liquid equilibrium (VLE) and vapor-phase pvTz properties predicted through molecular dynamics (MD) simulations are also presented. An isochoric apparatus was used to measure the properties for ten CO 2 mole fractions along ten isochores with specific volumes equal to (0.016846, 0.018521, 0.028775, 0.029922, 0.029931, 0.032358, 0.037241, 0.039089, 0.052176, 0.083492) m 3 kg −1 in the temperature and pressure ranges from (228.15 to 303.15) K and from (404.5 to 2519.9) kPa, respectively. The two-phase measurements were used to assess the VLE of the binary system by the flash method with the Peng-Robinson (PR) and PC-SAFT equations of state (EoSs), yielding average absolute relative deviations (AARDs) between experimental and calculated pressures of 0.20% and 0.19%, respectively. The values calculated with the PR and PC-SAFT EoSs showed qualitative agreement with the VLE properties from MD simulations, yielding AARD( p ) of 3.44 % and 3.32 %, respectively. The measurements carried out in the superheated vapor region were compared with calculations from the PR and PC-SAFT EoSs, obtaining low deviations (AARD( p ) of 0.38 % for the PR EoS and 0.33 % for the PC-SAFT EoS). Finally, a qualitatively good agreement between the MD simulations and the EoS calculations was also observed in the superheated vapor region (AARD( p ) of 1.02 % for the PR EoS and 1.00 % for the PC-SAFT EoS).