Experimental study and modelling of density and viscosity of near-Azeotropic mixture refrigerant R454B

The near-azeotropic mixture refrigerant R454B, composed of 68.9 % difluoromethane (R32) and 31.1 % 2,3,3,3-Tetrafluoropropene (R1234yf) by mass, has been promoted as an alternative to R410A and has gained wide applications. Thermophysical properties such as density (ρ) and viscosity (η) play crucial roles in heat and mass transfer processes. In this study, a vibrating-wire viscometer-densimeter (VWVD) was used to measure the ρ and η of R32, R1234yf, and R454B within a temperature range of 254 to 362 K and pressures up to 12.3 MPa. The obtained ρ and η values for R32 and R1234yf were compared with the reference equations implemented in REFPROP 10.0, with deviations mostly within the combined uncertainty. A Tait equation was applied to represent the ρ of R454B, with deviations mostly within 0.2%. A Vogel-Fulcher-Tammann (VFT) equation was used to correlate the η of R454B, where discrepancies were mostly within 3%. To extend the temperature, pressure, and composition range of the R32 + R1234yf mixtures, an extended hard sphere (EHS) model was developed using the experimental η data from this study and literature. Several mixing rules for the model were analyzed, but no significant improvement was found with an additional parameter. The performance of the EHS model without a binary parameter was compared with the extended corresponding states (ECS) model. The results showed that the EHS model had advantages in the high-density region. The EHS model developed in this study can reproduce the η of the R32 + R1234yf mixture mostly within 6% in the high-density region.