Pseudo-Leidenfrost phenomenon of low surface tension droplet induced by external aerodynamic field

Abstract

Droplet regulation has significant application potential in many fields; however, conventional controlling methods make it difficult to effectively control low surface tension droplets. Inspired by the Leidenfrost phenomenon, a pseudo-Leidenfrost system was established innovatively through micro-airflow rather than evaporated vapor to lift a droplet. Both experimental and numerical studies were carried out to investigate the pseudo-Leidenfrost effect of the FC3283 (perfluorotripropylamine) droplet. By FC3283, it is an extremely low surface tension working medium with thermal stability at room temperature. The oscillation of the droplet in the vertical direction was analyzed by tracking the position of the droplet centroid. The velocity of micro-airflow and pressure distributions at the bottom surface of the droplet, which were similar to the Leidenfrost phenomenon, were revealed. The mechanical analysis of the FC3283 droplet in a pseudo-Leidenfrost period was analyzed. Besides, the pseudo-Leidenfrost phenomenon of FC40 [FC-40 FluorinertTM Electronic Liquid] droplets with various Weber number was investigated. Weber number conditions for droplets triggering the pseudo-Leidenfrost phenomenon were revealed. The results showed that the motion of pseudo-Leidenfrost droplets in a period could be divided into three stages: falling, hovering, and rising. In the hovering stage, the Laplace force played an important role, which was the main reason for the rebound of the droplet, while the role of the aerodynamic force was to keep the droplet on the surface of the gas film. The Weber number had a significant influence on the pseudo-Leidenfrost phenomenon: droplets with a small Weber number tended to be absorbed by the micropores, while a too large Weber number would cause droplets to suspend or even leave. This study is helpful for controlling low surface tension droplets and laying a foundation for the transportation of low surface tension droplets.