A Dance of Ice and Fire: Compound Leidenfrost Films

The Leidenfrost effect is when an evaporating liquid, or a sublimating solid such as dry ice, levitates on its own vapor. Here, we demonstrate that a disk of frozen water placed on a sufficiently hot surface exhibits a compound Leidenfrost state, where both liquid and vapor films emanate from underneath the levitating ice. As the surface superheat temperature was increased, deposited ice exhibited four regimes: suppressed boiling, nucleate boiling, transition boiling, and the compound Leidenfrost state. The thicknesses of the compound Leidenfrost films were calculated by comparing their conductive heat transfer to their radial flow rates governed by Poiseuille’s law. The theoretical lifetime of melting Leidenfrost ice, assuming vapor/liquid layers of uniform thickness, was several times longer than that observed experimentally. We attribute this to the buoyancy of the vapor layer, which served to thin the overlying liquid film to enhance conductive heat transfer to the ice.