Comprehensive Thermodynamic Approach to Modeling Refrigerant-Lubricating Oil Mixtures

Abstract

A comprehensive thermodynamic approach for modeling mixtures of refrigerants and lubricating oils is presented. The new approach includes generalized methods for predicting the following thermodynamic properties of refrigerant-oil mixtures: bubble point temperatures, local oil concentrations, liquid specific heats and enthalpy changes during evaporation. Using this comprehensive method, heat release (enthalpy) curves are easily generated and also the effect of oil on the LMTD (log mean temperature difference) of evaporators can be modeled. Importantly, the definition of the boiling heat-transfer coefficient based on the bubble point temperature is included in the method. This new approach provides the basis for advances to be made in two-phase refrigeration heat-transfer research and design.