Delay of Leidenfrost point during drop impact of surfactant solutions

TL;DR

This study investigates how adding surfactants to water droplets influences the Leidenfrost temperature during impact, revealing that surfactant concentration and impact velocity significantly affect the boiling regimes and delaying the Leidenfrost point.

Contribution

It introduces a novel method of delaying the Leidenfrost point using surfactants and provides a detailed experimental analysis of the effects of impact parameters and surfactant concentration.

Findings

Surfactant addition increases the dynamic Leidenfrost temperature.

Impact velocity decreases the Leidenfrost temperature at fixed surfactant concentration.

A regime map of boiling behaviors as a function of impact conditions and temperature is developed.

Abstract

In this article, a novel method of increasing the dynamic Leidenfrost temperature is proposed through the addition of both anionic (SDS) and cationic (CTAB) surfactants to water droplets. We focus on understanding the hydrodynamics and thermal aspects of droplet impact Leidenfrost behaviour 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 were experimentally studied in details, covering a wide gamut of governing parameters. At a fixed impact velocity, increased with the increase of surfactant concentration. decreased with increase of impact velocity for all solutions of surfactant droplets at a fixed surfactant concentration. We proposed a scaling relationship for in terms of We and Oh. At temperatures (~ 400oC) considerably higher than , 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 behaviour is presented as function of impact We and substrate temperature (Ts). The findings may hold strong implications in thermal management systems operating at high temperatures