A New High-Pressure Viscometer for Oil/Refrigerant Solutions and Preliminary Results

The reliability and efficiency of refrigeration compressors is dependent on the lubricating effectiveness of the refrigeration oil, which is necessarily a solution of oil and refrigerant. In this article, the development of a high-pressure viscometer that can operate at elastohydrodynamic lubrication (EHL) inlet pressures for oil/refrigerant solutions is explained in detail. New viscosity measurements are presented for two compressor oils to 1.2GPa. Preliminary results are given for a polyol ester with two concentrations of R134a refrigerant to 0.35GPa. These are the first measurements of oil/refrigerant solutions to such high pressure. Temperature-pressure-viscosity correlations are applied to all materials for use in modeling. Correlations are provided for the temperature and pressure dependencies of the viscosity of the oils, refrigerant, and mixtures. The definition of pressure-viscosity coefficient is a pressing problem for elastohydrodynamics.