Geometrical parametric study of drop impingement onto heated surface with micro-pillar arrays

ABSTRACT In this study, the effects of wall temperature, micro-pillar array size, and micro-pillar height on the outcomes of the impingement of a single water drop impingement onto a heated surface with micro-pillar arrays were investigated. The micro-pillar arrays were designed with four different diameters and spacing (D, S: 5, 10, 15, and 20 μm) and three different heights (H: 20, 30, and 40 μm). For each type of surface, we classified the outcomes of drop impingement regimes into contact boiling, explosive lift-off, transition rebound, and Leidenfrost rebound by high-speed visualization. Micro-pillar arrays can result in the explosive lift-off behavior and increase the Leidenfrost temperature. The explosive lift-off occurs when the liquid-vapor interface is pushed up by vapor pressure. Based on the force balance analysis, the behaviors of the liquid–vapor interface were analyzed based on the competing wetting (capillary pressure) and non-wetting (vapor pressure) pressures to understand the explosive lift-off triggering mechanism.