Study of suppression of droplet Leidenfrost effect based on nickel foam surface

When the liquid film cooling droplets contact with the overheated wall, vapor layer is generated above the overheated surface, causing the droplets to bounce and thus fail to continue spread and evaporate on the heated surface. This Leidenfrost phenomenon has an adverse effect on the cooling performance of liquid film cooling droplets. Suppression of the Leidenfrost effect can be achieved by improving the surface material structure. However, the mechanism of inhibiting Leidenfrost effect based on metal foam surface is not yet clear. It is necessary to clarify its inherent mechanism firstly, so as to lay the foundation for guiding further optimization of the surface and achieving more efficient suppression effects. In this study, the Leidenfrost behavior of ethanol droplets on the nickel foam surface is investigated. The results show that increasing the pore diameter of nickel foam can effectively avoid the bouncing behavior of liquid film cooling droplets. This is attributed to the larger pore diameter of the metal foam skeleton, resulting in a larger internal gap and a smaller permeability resistance coefficient, which are conducive to the timely discharge of droplet vapor from the nickel foam skeleton. In addition, the surface wettability and thermal conductivity of nickel foam are effectively improved by compounding an appropriate amount of alumina particles. Compared with the untreated surfaces, the surface temperature threshold for ethanol droplet bouncing can be increased by up to 107 °C. The study provides a practical engineering strategy to enhance the cooling capability of liquid film cooling droplets on overheated surfaces, and has important potential in industrial cooling engineering.