Dynamic effects of droplet impingement on nanotextured surface for high efficient spray cooling

This study proposes the hydrodynamic characteristics of droplet impingement on heated surfaces and compares the effect of surface temperature when using water on a plane and nanotextured surface. Three samples are used: plane oxidized silicon, vertical CNTs and curved CNTs. Various surface temperatures, including single-phase (non-boiling) and two-phase (boiling) conditions, are included. Droplet impact velocity, transient spreading diameter and rebounding temperature are measured. Results show that the nanotextured surface enhances the heat transfer for evaporative cooling at lower surface temperatures, which is indicated by a shorter evaporation time. In the evaporative zone, the heat flux range of 30~40 W/cm², the mean heat transfer coefficient of the curved CNTs surface was approximately 140% higher than of the plane surface.