Drop collision with a hot, dry solid substrate: Heat transfer during nucleate boiling

Outcomes from an isothermal drop impact onto a surface (rebound, deposition, or splash) are determined by the impact parameters, liquid material properties, substrate morphology, and wettability. Drop impact onto a hot surface can be accompanied by Marangoni effects, nucleate or film boiling, and evaporation. The main focus of this experimental study is the characterization of the hydrodynamic outcome of a single-drop impact onto a hot surface. Drop impact phenomena have been observed and characterized using a high-speed video system. The impact parameters of the drop and the surface temperature have been varied. The observations lead to a classification of impact outcomes into several regimes: evaporation, nucleate boiling, foaming, transitional boiling, and film boiling. The contact time of the impinging droplet on the surface has been measured, and a model for this time and for the heat flux from the substrate to the drop has been proposed for the nucleate boiling regime. Comparison of model predictions to existing literature data is good.