Heat Transfer and Dynamic Characteristics in Double Droplets’ Impact on Radially Flowing Liquid Film

The process of droplet simultaneous impact and successive impact on the radial flow liquid film is investigated by three-dimensional numerical simulations. The effects of droplet horizontal spacing, vertical spacing, impact velocity, and jet flow rate on the interface evolution characteristics, temperature distribution, and convective heat transfer coefficient distribution are analyzed in detail. The results show that for the simultaneous impact of double droplets on the radial film, a clear middle crown wall is observed in the impact crater. Within a certain range, increases in the jet flow rate and droplet horizontal spacing enhance the cooling effect of the film and expand the area with a high heat transfer coefficient. Despite the fact that the heat transfer coefficient decreases slightly with the increase of impact velocity, the effect brought by impact velocity is not significant. In successive impacts, distinct primary and secondary crowns are produced. For heat transfer characteristics, increasing the jet flow rate increases the heat transfer area and the maximum heat transfer coefficient, but the droplet vertical spacing shows the opposite effects. With regard to the impact velocity, it still demonstrates no remarkable effect on the heat transfer coefficient. The present study provides a fundamental understanding of spray cooling involving multiple droplets' impact on liquid film.