Thermophysical Properties of a Refrigerant Mixture of R365mfc (1,1,1,3,3-Pentafluorobutane) and Galden® HT 55 (Perfluoropolyether)

This work presents a comprehensive experimental study of various thermophysical properties of an azeotropic refrigerant mixture of 65 mass% R365mfc (1,1,1,3,3-pentafluorobutane) and 35 mass% Galden HT 55 (perfluoropolyether). Light scattering from bulk fluids has been applied for measuring both the thermal diffusivity and the speed of sound in the liquid and vapor phases under saturation conditions, between 293K and the liquid–vapor critical point at 450.7K. Furthermore, the speed of sound has been measured for the superheated-vapor phase along nine isotherms, between 393 and 523K and up to a maximum pressure of about 2.5MPa. For temperatures between 253 and 413 K, light scattering by surface waves on a horizontal liquid–vapor iInterface has been used for simultaneous determination of the surface tension and kinematic viscosity of the liquid phase. With light scattering techniques, uncertainties of less than ±2.0%, ±0.5%, ±1.5%, and ±1.5% have been achieved for the thermal diffusivity, sound speed, kinematic viscosity, and surface tension, respectively. In addition to vapor-pressure measurements between 304 and 448 K, the density was measured between 273 and 443K using a vibrating-tube method. Here, measurements have been performed in the compressed- and saturated-liquid phases with uncertainties of ±0.3% and ±0.1%, respectively, as well as for the superheated vapor up to a maximum pressure of about 3MPa with an uncertainty between ±0.3% and ±3%. Critical- point parameters were derived by combining the data obtained by different techniques.