Dynamic behavior with rapid evaporation of an inkjet water droplet upon collision with a high-temperature solid above the limit of liquid superheat

The dynamic behavior of the rapid evaporation of an inkjet droplet of water upon collision with a high-temperature silicon substrate has been investigated experimentally. The colliding droplet spreads into a thin disk-shaped liquid film and then splashes away. The splashing behavior depends on the solid temperature, which varies significantly due to nucleation and evaporation while spreading along the solid surface. Even when the temperature of the contact interface of the substrate, as estimated by transient heat conduction, significantly exceeds the kinetic limit of liquid superheat, numerous fine bubbles are simultaneously generated, presumably by spontaneous nucleation, beneath the liquid film and break up the film, which is dispersed into fine droplets. The surface temperature at the collision point is measured using a small platinum film sensor and exhibits a significant decrease compared to the heat conduction to the liquid for this peculiar nucleation. (C) 2017 Elsevier Ltd. All rights reserved.