Observations of initiation stage of spontaneous vapor explosions for droplet scale

Abstract

In this study, the initiation stage of spontaneous vapor explosions generated by single droplets of molten tin submerged in water was investigated using a highspeed video camera operated with a reflected light system. Photographs of the formation process of vapor film, the process of vapor film disturbance, and the initiation process of the vapor explosions for different masses of molten tin and different nozzle diameters were obtained. The results demonstrate that partial thermal interaction between tin and water does not cause a vapor explosion with fragmentation. The vapor film disappears locally during the formation of the vapor film around the hot liquid droplet. Direct contact between the hot molten tin surface and water is thereby generated. However, the local disappearance of the vapor film does not progress and the vapor film is reconstructed. A vapor explosion occurs when the vapor film collapses at the local area of the bottom or edge of the disk-shaped droplet.