Levitation Time Measurement of Water Drops on the Surface of Liquid Nitrogen

Abstract

The levitation of water drops on the surface of liquid nitrogen is studied. The water drop evaporates the liquid nitrogen, which makes a nitrogen vapor film between the water drop and the surface of the liquid nitrogen. The temperature of the drop falls from the initial temperature of the drop to the melting temperature and then eventually reaches the Leidenfrost temperature at which an ice sphere falls into the liquid nitrogen. The floating time of the water drop on the surface of liquid nitrogen corresponds to how long the temperature of the water drop takes to go from the initial temperature to the Leidenfrost temperature. We measured the floating time of the water drop on the surface of the liquid nitrogen as a function of the size of the drop and the initial temperature of the drop. The floating time increases linearly with increasing drop size and increases linearly with increasing initial temperature of drop, which can be explained reasonably well by assuming uniform cooling of the drop by heat conduction.