The design and construction of a refrigerant flow loop for the evaluation and calibration of oil concentration sensors is presented. Capabilities of the flow loop are demonstrated with the results of an initial series of experiments using mixtures of R-22 and a naphthenic mineral oil. These experiments provided preliminary data on the performance of two potential oil concentration sensors: a vibrating U-tube densimeter and an ultrasonic acoustic velocity sensor. Experimentally determined values of specific gravity and acoustic velocity in the flowing oil-refrigerant mixtures are included°

Units: Dual