Experimental investigation on heat transfer of a single droplet during collision with a heated wall above Leidenfrost temperature

The correlation was derived based on the mechanistic model of Baumeister4 for film boiling heat transfer coefficient of a Leidenfrost droplet floated on a heated surface. The model was formulated only with the physical parameters of the stationary droplet while the droplet collision heat transfer phenomenon is very dynamic. Therefore, it is needed to improve the existing prediction correlation for droplet-wall collision heat transfer by incorporating dynamic characteristics of collision droplets into heat transfer coefficient model. In this study, effects of droplet velocity on collision dynamics and heat transfer characteristics during droplet-wall collision beyond the Leidenfrost point were examined using the integrated high-speed visible and infrared (IR) imaging technique. The experimental results obtained from the synchronized HSV and IR measurement could provide a better understanding than the previous existing results because various physical parameters associated with droplet-wall collision dynamics and heat transfer phenomena can be simultaneously obtained and the relation between collision dynamics and local heat transfer characteristics can be examined. This study experimentally investigated the dynamic behavior and heat transfer characteristics of droplet. The tests were conducted using a water droplet with diameter of 2 mm at atmospheric pressure. Droplet with velocity in the range from 0.2 to 1.5 collided with heated wall