3180 (RP-356) -- Measuring the Concentration of a Flowing Oil-Refrigerant Mixture with a Bypass Viscometer PDF

A recently introduced bypass viscometer was evaluated as a sensor for measuring the concentration of oil in the liquid line of a refrigeration system. The viscometer was tested under simulated liquid-line conditions with R-12/naphthenic oil, R-22/naphthenic oil, and R-502/alkylbenzene oil mixtures in concentrations of 0 to 30 weight-percent. All of the oils used were of the 150 SUS viscosity classification. Test temperatures in the simulated liquid line ranged from 70 to 120 F (21.1 to 46.1°C) at pressures corresponding to approximately 3 F (1.7°C) subcooling. Statistical analysis of the data showed that the viscometer can be used measure the flowing oil concentration in R-12/naphthenic oil mixtures with an uncertainty of ±1 weight-percent or less for all of the test conditions. For the R-22/naphthenic oil and R-502/alkylbenzene oil mixtures, the measurement uncertainty increased to ±2 weight-percent at the higher test temperatures for oil concentrations below approximately 10 weight-percent.

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