Theoretical study and experimental verification of the viscosities of azeotropic refrigerant R515B

One essential aspect of the studies on the refrigeration and heat pump technology is to search for new alternative working fluids. Meanwhile, the azeotropic mixtures of hydrofluorocarbons (HFCs)/hydrofluoroolefins (HFOs) have attracted researchers not only in fundamentals research field but also in the industry fields due to its good performance and applicability. Therefore, to promote application research, this study is focused on the characteristics of viscosity for azeotrope R515B, which is widely recognized and studied from the thermodynamic aspect. Hence, the high-pressure density and viscosity in liquid phase of R515B were measured with a vibrating-wire viscosimeter within the temperature range in 253 K to 363 K when pressure changes from 1 MPa to 12 MPa. The combined expended uncertainties with a confidence level of 0.95 (k = 2) of density and viscosity are 0.2 % and 2 %, respectively. In addition, a modified viscosity model is proposed with combining the parameterization method of thermodynamic equation of state (EoS) in previous work and the modified entropy variable as well as reduced viscosity reference term of residual entropy scaling (RES) theory. Furthermore, the systematical comparison results among this model and three benchmark viscosity models available illustrate that the RES model proposed in this research is robust and precise in a wide range of operation condition.