Dynamic Wetting Behavior During Droplet Impacting on a Superheated Surface

Abstract

During the reflooding process after a loss-of-coolant-accident (LOCA) scenario, the highly superheated fuel surface of the reactor core will undergo a quenching process. The temperature of the fuel element surface drops sharply during the quenching process, because large droplets can pass through the vapor film to re-wet the wall surface, and the boiling mechanism is transformed from film boiling to nucleate boiling, the boiling heat transfer perfomance is greatly improved. But the transition of the boiling mechanism is closely related to the initial velocity of the droplet, the size of the droplet, and the wall temperature. At the same time, after the droplets hit the wall surface, dynamic wetting behaviors such as deposition, vibration, rebound, or splashing will occur. Unfortunatly, the mechanism of droplet wetting behavior on boiling heat transfer is not clear, so it is necessary to carry out a fundamental research. In this study, the droplet size, initial droplet velocity, substrate’s temperature and surface tilt angle were precisely controlled. The images were captured by a high-speed camera to obtain a dynamic wetting image of the droplets impacting the wall from room temperature to 400°C. Finally, based on the image analysis method, a simple analysis of the three-phase contact line movement and the droplet dynamic wetting behavoir is performed.