Augmenting the Leidenfrost Temperature of Droplets via Nanobubble Dispersion

Abstract

Droplets may rebound/levitate when deposited over a hot substrate (beyond a critical temperature) due to the formation of a stable vapor microcushion between the droplet and the substrate. This is known as the Leidenfrost phenomenon. In this article, we experimentally allow droplets to impact the hot surface with a certain velocity, and the temperature at which droplets show the onset of rebound with minimal spraying is known as the dynamic Leidenfrost temperature (T DL ). Here we propose and validate a novel paradigm of augmenting the T DL by employing droplets with stable nanobubbles dispersed in the fluid. In this first-of-itskind report, we show that the T DL can be delayed significantly by the aid of nanobubble-dispersed droplets. We explore the influence of the impact Weber number (We), the Ohnesorge number (Oh), and the role of nanobubble concentration on the T DL . At a fixed impact velocity, the T DL was noted to increase with the increase in nanobubble concentration and decrease with an increase in impact velocity for a particular nanobubble concentration. Finally, we elucidated the overall boiling behaviors of nanobubble-dispersed fluid droplets with the substrate temperature in the range of 150− 400 °C against varied impact We through a detailed phase map. These findings may be useful for further exploration of the use of nanobubble-dispersed fluids in high heat flux and high-temperature-related problems and devices.

Self-Propelled Polymeric Droplet in Leidenfrost State on a Superheated Ratchet Surface

“…In this case, the droplet rises above its vapor cushion, which acts as a thermal insulator. Therefore, the droplet exists on the superheated surface for more than 300 s without instantaneous evaporation, which is well-known as the Leidenfrost effect. , The Leidenfrost temperature above which the droplet begins to levitate and droplet dynamics depend on various factors, for example, the impinging velocity of the droplet to the surface roughness/structure, − material, − and droplet species. ,,− According to Bouillant et al, it was observed that some vortices that are expected to induce mixing occur within the Leidenfrost droplet. In addition, it is considered that the temperature within the droplet is uniform and approximately saturated, owing to excellent mixing.…”