Abstract:

The phenomenon of droplet coalescence-induced self-propelled jumping is of great significance in enhancing heat transfer, preventing frosting and defrosting in heat pump air conditioning systems. The processes of droplet coalescence and self-propelled jumping are modeled independently in consideration with the released surface energy, gravity potential energy, the viscous dissipation and surface tension energy dissipation caused by contact angle hysteresis. The simulation values are in accordance with existing experimental data in the literature. It was found that the number of droplets, the uniformity of the radius and the surface characteristics do affect the process of coalescence and self-propelled jumping. With the increasing of droplet numbers, the critical contact angle in process of coalescence decreases from 120° to 105°. The critical contact angle in process of self-propelled jumping decreases from 140° to 130° with the increasing of uniformity of droplet radius. The results indicate that larger droplet number and higher uniformity of droplet radius are beneficial for coalescence and self-propelled jumping. In addition, the influence of solid-liquid contact fraction on the process coalescence and self-propelled jumping decreases with the increase of contact angle.