Effects of Droplets' Collision on Heat and Mass Transfer between High-Temperature Gas and Micron Water Droplets

The heat and mass transfer process between gas and micron water droplets is complicated. During the process, the collision of droplets can affect the evaporation rate of droplets, and the heat and mass transfer between two phases as well. Unsteady numerical simulation was done in this paper to investigate the effect of droplets' collision on the heat and mass transfer. The results show that after the water droplets collide and combine together, the total heat transfer area decreases, thus the accelerated rate of droplet temperature drops. As a result, the unsteady time of droplet temperature rising with considering droplets' collision in calculation is longer than that of without considering droplets' collision. After droplets collide and combine together, the evaporation rate drops, thus the droplets survival time and time for evaporating completely are extended. The steady gas temperature with droplets' collision is higher slightly than that without droplets' collision, which indicates that the droplets' collision affect the results by using numerical prediction. Against the experimental data, the predicted results with droplets' collision are more believable than that without collision. Considering the droplets' collision and combination, the change rate of the droplets' diameter drops, thus the gas velocity picks up slowly.