Numerical Study of Leidenfrost Droplet Behavior on Hot Porous Substrate

Abstract The Leidenfrost droplet refers to the phenomenon where a liquid droplet instantaneously contacts a high-temperature surface, forming a vapor film that suspends it above the surface. To overcome the increased heat resistance and deteriorated heat transfer caused by this Leidenfrost effect, the surface texturing can be employed to increase the Leidenfrost point. In this study, a VOF phase-change model coupled with species transport models was established to investigate the phase-change, spreading, and permeation processes of droplet on high-temperature porous surfaces. Furthermore, the effects of heating surface temperature (150 °C–350 °C), Darcy number (1 × 10−4 to 2.25 × 10−5), and droplet impact velocity (0.2 m/s–0.6 m/s) on the droplet dynamics were explored. The obtained results indicate that, due to the competition between capillary forces from the porous structure and vapor expansion, the porous surface exhibits a delaying effect on the Leidenfrost phenomenon compared to smooth one. With an increase in Darcy number, the permeation of vapor strengthens, making it harder to form a vapor film and thereby increasing the Leidenfrost point. Moreover, a lower Darcy number leads to an increased droplet bounce frequency on porous surface. Additionally, the droplet fragmentation occurs at both low and high We numbers, while a relatively stable vapor film formation is achieved at moderate, We numbers.