An acoustic velocity sensor was constructed for the measurement of oil cortcentration in the liquid line of a refrigeration system. The sensor 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 acoustic velocity sensor can be used to measure the flowing oil concentration with an uncertainty of ±1 weight-percent or less for nearly all of the test conditions.

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