Hysteresis and Hydrodynamic Collapse in Leidenfrost Vapor Layers

During the Leidenfrost effect, a thin insulating vapor layer separates an evaporating liquid from a hot solid. Here we show that Leidenfrost vapor layers can be sustained at much lower temperatures than those required for formation. We use an electrical technique with microsecond resolution to measure the thickness of the vapor and find that explosive failure occurs at temperatures and thicknesses that do not depend on material and fluid properties, such as thermal conductivity or salinity, for smooth, metallic surfaces. Numerical simulations confirm that the hydrodynamic flow of the vapor determines the lowest possible temperature for maintaining stable Leidenfrost films.