Enhanced interfacial boiling of impacting droplets upon vibratory surfaces.

ABSTRACT

HYPOTHESIS: Despite the flourishing studies of droplet interfacial boiling, the boiling upon vibratory surfaces, which may cause vigorous liquid-vapor-solid interactions, has rarely been investigated. Enhanced boiling normally can be gained from rapid removal of vapor and disturbance of liquid-vapor interface. We hypothesize that the vibratory surfaces enhance both effects with new intriguing phenomena and thus, attain an enhanced boiling heat transfer. EXPERIMENTS We experimentally investigated the impacting fluid dynamics and coupled heat transfer patterns of multiple droplets and a single droplet impinging on still and vibratory surfaces of various materials and different wettability. FINDINGS: The boiling under vibratory surfaces with increased vibration velocity amplitude and enhanced wettability can be enhanced by 80% in heat transfer coefficient and Nusselt number, which is attributed to several reasons shortened bubble lifespan, thinner and smaller bubbles, and enhanced disturbances in liquid-vapor interfaces. The vibration also delays the Leidenfrost point when the droplet impacts a descending surface, which shows that the droplet impact moment (vibration phase angle) is particularly crucial. The descending surface releases the generated vapor actively and facilitates liquid-solid contact, thereby delaying the Leidenfrost. From fundamentals to application, this article strengthens our understanding of vibrated interfacial boiling in scenarios closer to multiple natural processes and practical industries.