Measurement and Prediction of the Viscosity of Refrigerant-Lubricant Mixtures

The viscosity of dense fluid mixtures is important in numerous applications, including the design of refrigeration equipment in which mixtures of light refrigerant molecules with heavy lubricant molecules are encountered. There is presently no well-founded theoretical approach able to predict this important property in such cases where the molecules differ greatly in size. In this project, we will develop a new kinetic theory for the viscosity of an important class of model fluids: mixtures comprising chains of hard spherical segments. Next, we will develop a methodology whereby this new theory can be used to predict the viscosity of a real fluid mixture provided that the viscosities of the constituent pure fluids are known. In parallel with this, we will make measurements of the viscosity of refrigerant-lubricant mixtures against which to validate the new methodology.The theoretical aspects of this project are ambitious and will result in significant advances in what is a difficult field. The results will have applications not only in refrigeration technology, as highlighted in the proposal, but far beyond and they will reduce the present reliance upon empirical models.