Experimental and numerical study on the impact and freezing process of a water droplet on a cold surface

摘要

Ice accretion on cold solid surfaces presents hazards to a broad range of applications. It is quite essential to understand the dynamic and freezing mechanism of water droplets on a cold solid substrate for the prevention of ice accretion. In this study, the impact and freezing process of water droplets was studied experimentally and numerically. The effects of substrate temperature on the whole processes were investigated through changing the surface temperature from room temperature 25 degrees C to -30 degrees C. The results showed that the decrease of surface temperature led to the decrease of retraction rate, equilibrium droplet height after oscillation, freezing delay time and freezing time, while increased the final contact area due to the lower viscous dissipation energy. Also, a numerical model was developed to investigate the impact and freezing process of water droplets on an ultra-cold surface (-100 degrees C to -40 degrees C). The predicted droplet impact morphology, dynamic characteristics (spreading factor) and the propagation of freezing front were compared with experimental results, which exhibited good agreements. The numerical results suggested that the final contact area decreased slightly with the drastic decrease in surface temperature when the surface temperature is below -40 degrees C. Moreover, the influence of surface temperature on freezing front propagation and freezing time were analyzed in detail from the numerical results.