Numerical Study of Spherical Vapor Layer Growth Due to Contact of a Hot Object and Water

Vapor film formation and growth due to contact of a hot body and other liquids arise in some industrial applications including nuclear fuel rods, foundry and production of paper. The possibility of a steam explosion remains in most of these cases which could result in injuries and financial damage. Due to the importance of such phenomenon, this study deals with vapor layer forming, growth, and its internal pressure. A mathematical model of a molten spherical droplet immersed in water has been developed, and the results of the numerical solution are discussed. The effects of changing various characteristics (e.g. hot body size, temperature, and hydrostatic effects, as well as the temperature of bulk fluid) were investigated. These parameters affect the vapor layer size, vapor internal pressure, and the saturated temperature at the interface between vapor and liquid phases. Finally, conclusions indicate that the internal vapor pressure jumps, being up to several times larger than that of the initial condition. These pressure pulses and related vapor layer thickness variations could cause thermal fragmentation of the droplet which in turn results in strong pressure shock build-up due to small pieces of the droplet in contact with the water, which could then escalate to become a propagating large-scale vapor explosion. The vapor explosions could be hazardous and threaten the system safety.