Cooling effect of droplet impacting on heated solid surface

This paper presents the outcomes and mechanisms of single droplet impacting on a heated solid surface with changing temperature. Two noncontact measurement techniques including a Thermal Infrared Imager and a High-speed Digital Recording Camera were adopted in the experiments to explore the cooling effect of the droplet on the heated surface with varying temperatures and to record the typical phenomena, respectively. Four typical impact regimes including flattening, bubble, transition from bubble to atomization and atomization during the droplet impact were observed and a comprehensive map based on non-dimensional analysis was built to describe the relationships among the typical regimes. For quantitative analysis, the empirical correlations were acquired to predict the non-dimensional maximum spreading diameter based on non-dimensional analysis. The non-dimensional droplet resident time decreases linearly with the increase of T w T s a t log 10 Re . The heat flux of average droplet was calculated and the result showed that it increases with the non-dimensional parameter T w T s a t log 10 Re .The transient temperature of the heated surface was measured to quantify the effectiveness of cooling.