The Nature-inspired fluids and interfaces lab at Virginia Tech has a research project on boiling ice.
If you put a few drops of water on a hot skillet, they'll levitate, sliding around the pan with wild abandon. Physicists at Virginia Tech have discovered that a thin, flat disk of ice can be placed on a heated aluminum surface. Before the ice disk will levitate, there must be a much higher critical temperature achieved.
In 1756, a German scientist named Johann Gottlobfrost reported his observation of the unusual phenomenon. He noted that water splashes onto a hot pan sizzles and leaves a trail. gleaming drops resembling quicksilver will form if the pan's temperature is above water's boiling point. The "Leidenfrost effect" is in his honor.
Physicists came up with a viable explanation for why this happens. If the surface is above the boiling point of water, the steam and water will form underneath them, keeping them levitated. The temperature at which the Leidenfrost effect will manifest will be different.
Physicists discovered that the drops aren't just riding along on a cushion of steam; as long as they are not too big, they also propel themselves. The fluid flow inside the Leidenfrost drops, acting like a small internal motor. The large drops showed a balanced flow, but as the drops evaporated, they became smaller and more spherical. The downward tilt in the same direction the fluid in the droplet flowed helped to cause the drops to roll like a wheel. The French physicists called their discovery a "Leidenfrost wheel".
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The source of the cracking sound was finally identified by an international team of scientists. It depends on the size of the droplets. Smaller drops will skitter off the surface and evaporate, while larger drops explode with that telltale crack. As the droplets shrink, the concentration of contaminants will increase. The particles form a kind of shell around the droplet as they end up with a high concentration. When it hits the surface, that shell causes the drop to explode.
MIT scientists determined last year that the droplets are propelled across a heated oily surface 100 times faster than on bare metal. A thin coating formed outside each droplet, like a cloak, under the right conditions. As the oil got hotter, tiny bubbles of water vapor formed between the oil and the droplet. Subsequent bubbles formed near the same spots, forming a single vapor trail that pushed the droplet in a preferred direction.
Is it possible to achieve the Leidenfrost effect with ice? The Virginia Tech team wanted to ask the question about levitating ice. It was a project of curiosity. The question of whether or not it was possible to have a three-phase Leidenfrost effect with solid, liquid, and vapor was what drove our research.