4310 (RP-761) -- Real-Time Determination of Lubricant Concentrations Dissolved in Alternative Refrigerants PDF

A methodology was developed and used to measure both polyolester lubricant concentrations in solution with R-134a and R-407C and mineral oils in solution with R-123. This method is unaffected by changes in pressure, temperature, refrigerant type, and lubricant type. 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 body viscometer. Lubricant concentrations determined by HPLC compared favorably with the ASHRAE Standard 41.1 method (ASHRAE 1984). Circulating lubricant, miscible and immiscible, concentration in identical R-407C operating systems was also measured to demonstrate the practical application of the test method.

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