Dynamic behavior and micro-explosion characteristics of impinging droplets on a high-temperature surface

The dynamic behavior and micro-explosion characteristics of impinging droplets on a hot surface were examined experimentally. A 2.3 mm sized, de-ionized water droplet was made through a 31G injection needle. A sapphire plate was heated up to 300 degrees C on a hotplate. Two high-speed cameras at a frame rate of 4,000 fps were used for visualization. The Weber number was changed from 5 to 117 by changing the initial height of the droplet from 10 to 210 mm. The hydrophobic characteristics were observed when the temperature of hot surface was over the Leidenfrost point. Dynamic behavior was strongly dependent on the Weber number, and a splashing phenomenon occurred when the Weber number was higher than 50. A micro-explosion was observed at high Weber number under Leidenfrost conditions before splash. From the PIV measurement, the micro-droplets after the explosion jetted at a considerably high speed compared to the impinging velocity.