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 mu m) and three different heights (H: 20, 30, and 40 mu m). 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-offbehavior 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. (C) 2020 Elsevier Ltd. All rights reserved.