Experimental quantification of partial melting in a single frozen drop

The visualization and quantification of the melting process of a single frozen droplet was conducted. Luminescent dye and high-speed camera visualization were used to monitor the partial melting state of an ultrasonically levitated frozen drop exposed to warm environments. Rhodamine B was dissolved (0.01% mass fraction) in the water used to create a droplet. The Droplet was placed at the node of the wave created by the acoustic levitator and frozen via convective cooling. When the cold air flow was turned off, the partial melting of the droplet began. Water droplets with a diameter ranging approximately between 300μm to 1800μm were tested. Four environmental melting temperatures were tested: 5°C, 15°C, 25°C and 35°C. A laser beam was pointed at the partially melted drop to enhance the luminesce behavior of the Rhodamine B molecules in the water. The luminescence of the ink in the melted water allowed for the discretization between frozen ice and melted water. The variation of percentage of partial melting of the drop with time was recorded. The correlation between the rate of melting, environmental temperature, and diameter of the frozen droplets is reported and discussed in this paper. It is confirmed that the time rate of melting is inversely proportional to the diameter of the ice crystals and directly proportional to the environmental temperature. An empirical fit to predict the percentage of partial melting with respect to temperature and droplet diameter was experimentally acquired.