Postponement of dynamic Leidenfrost phenomenon during droplet impact of surfactant solutions

In this article, a novel method of increasing the dynamic Leidenfrost temperature T DL is proposed by adding both anionic (SDS) and cationic (CTAB) surfactants to water droplets. We focus on understanding the hydrodynamics and thermal aspects of droplet impact Leidenfrost behavior of surfactant solutions and aim to delay the onset of the Leidenfrost regime. The effects of Weber number ( We ), Ohnesorge number ( Oh ), and surfactant concentration on dynamic Leidenfrost temperature ( T DL ) were experimentally studied in detail, covering a wide gamut of governing parameters. At a fixed impact velocity, T DL was increased with increase of surfactant concentration. T DL decreased with the increase of impact velocity for all solutions of surfactant droplets at a fixed surfactant concentration. We proposed a scaling relationship for T DL in terms of We and Oh. At temperatures (∼ 400 °C) considerably higher than T DL , droplets exhibit trampoline-like dynamics or central jet formation, associated with fragmentation, depending upon the impact velocity. Finally, a regime map of the different boiling regimes such as transition boiling, Leidenfrost effect, trampolining, and explosive behavior was presented as a function of impact We and substrate temperature ( T S ). The findings may hold substantial implications in thermal management systems operating at high temperatures.