Modeling of Fragmentation of Melt Droplets Triggered by Boiling Effect

The thermal fragmentation process of melt droplets in an energetic fuel coolant interaction is investigated. Boling effect is considered to be the triggering event, during the transition of heat transfer mode from film boiling to nucleate boiling and coolant periodically contacting with the droplet surface. The vapor bubble around droplet becomes unstable and collapses toward the surface of the droplet which induces the fragmentation of melt droplets. The vapor bubble collapse is modeled by writing a momentum equation for vapor bubble dynamics, an energy equation for each region of the droplet, coolant vapor and liquid and linking each region by the appropriate boundary conditions. And then a thermal fragmentation model triggered by boiling effect is developed and verified. By using the developed model, the fragmented mass of the droplet triggered by boiling effect is calculated. The result shows that the fragmentation rate is larger than that given by hydrodynamic model.