Condensing Phenomena of Single Vapor Bubble into Subcooled Water : 1st Report, Flow Visualization

Abstract

Experiments have been carried out to investigate direct contact condensation of saturated vapor bubbles introduced into a quiescent subcooled water environment. The experiments were performed for a range of pressures from atmospheric to 1 MPa, for subcooling from 10 to 70°C, and for initial bubble diameters of about 10 mm. Flow visualization by high speed motion pictures was based on a frame by frame analysis. The photographs showed that the successive shapes of the bubbles during their collapse histories proceeded from a sphere to a hemisphere, to an ellipsoid, to a sphere, and finally to collapse. Two-dimensional photographs showed that the cavities of the bubbles during their collapse histories proceeded from the bottom to the top. The time to collapse increased with increasing pressure and with decreasing temperature difference. The rising velocities of the bubbles were essentially constant, with an overall range of 20∼25 cm/s.