RP-761 -- Real Time Determination of Lubricant Concentrations Dissolved in Alternative Refrigerants PDF

A methodology has been developed and used to measure polyolester lubricant concentrations in solution with R-134a and R-407C and mineral oils in solution with R-123. This method is transparent to pressure, temperature, refrigerant type and lubricant type changes.

The concentration of dissolved lubricant was measured in three alternative refrigerants with two different synthetic polyolesters and two different mineral oils over a temperature range of 68°F (20°C) to 140°F (60°C) and a concentration range of 0 to 6% w/w. The evaluation methods included density, viscosity and high pressure liquid chromatography (HPLC). Measurements of viscosity and density were performed on an oscillating bob viscometer. Lubricant concentrations determined by HPLC compared favorably with the ASHRAE 41.1 method (1984). Determinations of circulating lubricant, miscible and immiscible, in R-407C using identical operating systems were also made to demonstrate the practical application of the test method.