Study on Vapor Explosion Mechanism Related to Vapor Condensation

In order to clear the mechanism of the vapor explosion, two kinds of experiments were performed. In the experiment 1, an upper side-open transparent vessel filled with molten metal (solder, tin, lead and zinc) was immersed in the water tank. It was found that vapor cavities were generated in the metal and the vapor bubble connected with a cavity collapsed just before the occurrence of a vapor explosion. In the experiment 2, the apparatus consists of a water tank and a heated vessel with a cavity. Subcooled water in the water tank flows into the vapor cavity, immediately after the pressure in cavity is abruptly reduced because of the vapor condensation. Then the pressure rises rapidly by the vaporization of water in the cavity. A chain of phenomena, the generation of vapor cavities, the pressure descent due to vapor collapse, the water inflow into the cavity, and the rapid pressure rise, can be a part of the process of vapor explosion. The relation between the metal temperature just before the occurrence of a vapor burst and the minimum film boiling temperature criterion of Dhir and Purohit was investigated.