Solubility, density and viscosity of mixtures of isobutane (R-600a) and a linear alkylbenzene lubricant oil

Isobutane (R-600a) is a well established environmentally friendly substitute for hydrofluorocarbon and chlorofluorocarbon refrigerants in vapor compression refrigeration applications. In order to improve the performance and reliability of compressors and refrigerators, the behavior of the thermophysical properties of refrigerant–lubricant mixtures must be well understood, as the choice of lubricant oil plays an important role in determining the system equalizing pressure and in minimizing the friction losses in the compressor. Solubility, density and viscosity data for a system (i.e., several mixtures of the same components) of R-600a and a linear alkylbenzene lubricant oil (LAB ISO 5) were obtained experimentally at temperatures between 23 and 80 °C. The solubility and density data were correlated with the Peng–Robinson equation of state with a single interaction parameter. The dynamic viscosity data were predicted with an Eyring-type model in which the excess activation energy for viscous flow was modeled in terms of the excess Gibbs free energy derived from the Peng–Robinson equation of state.