Photographic Observations of Bubble Formation in Flashing Nozzle Flow

Abstract

Visual observations have been made of bubble growth in the nucleation region of flashing flow of initially subcooled water in a converging-diverging nozzle. Experiments performed under various flow rates, saturation temperatures, turbulence levels, noncondensable gas content, and artificial nucleation sites failed to produce isolated spherical bubbles of the size or density predicted by common bubble nucleation and growth models. Heterogeneous nucleation in the bulk flow was never observed and it is concluded from bubble growth rates that the role of convection in the heat and mass transfer environment of the bubbles is an important consideration in the physics of flashing flows near the nucleation region.