Experimental Investigation on Impact Behavior and Leidenfrost Phenomenon of Droplets on ATF Cladding Surfaces

In order to investigate the Leidenfrost phenomenon of droplet impact on ATF (accident tolerance fuel) claddings, the impact behavior of droplet on sintered SiC and FeCrAl is recorded by high-speed camera, and Zr-4 is chosen as a reference. Based on the visualization results, the droplet impact behavior can be categorized into five regimes, i.e. deposition, rebound with secondary atomization, breakup with secondary atomization, rebound and breakup. Deposition corresponds to nucleate boiling. Rebound and breakup correspond to film boiling, and the rest two impact regimes are corresponding to transition boiling. It is found that the CHF temperature is relatively insensitive to Weber number, while the Leidenfrost temperature increases with Weber number and solid thermal effusivity. During film boiling, the droplet spreading dynamics seems to be independent of the surface temperature. As the Weber number increases, the droplet spreads more rapidly, and reaches a larger spreading diameter.