Dynamic Behavior of Liquid Droplet Impacting on Heated Surfaces

The study of a single droplet impact and spread on a heated surface is motivated by its strong relevance to spray cooling technology. The generic view on the study of the spray cooling process exhibits the synthesis of fluid mechanics, heat transfer and surface thermodynamics. Due to the complex phenomena involved, no comprehensive theoretical models are available. The few works that appeared in the literature so far have been largely empirical; the applicability of several correlations proposed is limited. This book chapter reports an experimental study of fundamental aspects of the dynamic characteristics of a single droplet impacting on a heated surface. In this experiment, the entire dynamic process of a droplet from the moment of collision with the substrate surface including the rebound was visualized and analyzed using a high-speed CCD camera. The experimental study focused mainly on the spread of a liquid droplet under the influences of substrate temperature varying from 26°C to 240°C, the inclination angle of substrates at 0°, 30°, and 60°, the wettability of substrates with contact angles from 30° to 90°, the viscosity of liquids ranging from 0.00089 up to 0.9161 kg/m.s, and surfactants of different concentrations.

Keywords: Droplet spreading, sessile droplet heat transfer, spray cooling.