HIGH-PRESSURE OPTICAL MEASUREMENTS OF SIZES, VELOCITIES AND LONGITUDINAL POSITIONS OF BUBBLES

This paper presents an optical system for taking shadow photographs of bubbles in a high-pressure evaporator tube. With this system and inte rpretation principles, not only the size and velocity of a bubble can be calculated from its shadow images on photos, but also its longitudi nal position on the optical axis may be estimated from the size of a ' 'bright spot'' in its shadow image. A simple relation based on geometr ical optics is applied. Performance of the new system and validity of the interpretation principles were examined through three series of ca libration tests. Relative deviations of estimations to actual values o f sizes and longitudinal positions of bubbles are within 1 and 5% resp ectively. Application at high-pressure was successful. Due to the gene ral nature of the system and the interpretation principles, results ma y be extended to more dispersed two-phase flow situations.