MOMENTUM • VIRGINIA TECH MECHANICAL ENGINEERING 13 student Daniel Cusumano . What he observed was fascinating . Even when the aluminum was heated above 150 C , the ice did not levitate on vapor as liquid does . Cusumano continued raising the temperature , observing the behavior of the ice as the heat increased . What he found was that the threshold for levitation was dramatically higher : 550 C ( 1022 F ) rather than 150 C . Up until that threshold , the meltwater beneath the ice continued to boil in direct contact with the surface , rather than exhibit the Leidenfrost effect .
What was going on underneath the ice that prolonged the boiling ? The project was picked back up by graduate student Mojtaba Edalatpour a short time later , to solve the mystery . Edalatpour had been working with Boreyko to develop novel methods of heat transfer and put that knowledge to work in approaching this problem . The answer turned out to be the temperature differential in the meltwater layer beneath the ice . The meltwater layer has two different extremes : Its bottom is boiling , which fixes the temperature at about 100 C , but its top is adhered to the remaining ice , which fixes it at about 0 C . Edalatpour ’ s model revealed that the maintenance of this extreme temperature differential consumes most of the surface ’ s heat , explaining why levitation was more difficult for ice .
Boreyko elaborated . “ The temperature differential the ice is uniquely creating across the water layer has changed what happens in the water itself , because now most of the heat from the hot plate has to go across the water to maintain that extreme differential . So only a tiny fraction of the energy can be used to produce vapor anymore .”
The elevated temperature of 550 degrees Celsius for the icy Leidenfrost effect is practically important . Boiling water is optimally transporting heat away from the substrate , which is why you feel ample heat rising from a pot of water that is boiling but not from a pot of water that is merely hot . This means that the difficulty in levitating ice is actually a good thing , as the larger