Numerical investigation of Weber number and gravity effects on fluid flow and heat transfer of successive droplets impacting liquid film

Droplet-based high heat flux dissipation technique under multi-gravitational environments has gained increasing research attention due to the increased requirements of heat dissipation in advanced air-/space-borne electronics. In this paper, a three-dimensional model was developed to investigate the impact of continuous droplets on liquid film under various Weber numbers and gravity loads. In other words, the effects of Weber number and gravity load on the flow and heat transfer characteristics were investigated. The results demonstrated that the dissipated heat flux was positively correlated with both Weber number and gravity load. A large Weber number indicated larger kinetic energy of a droplet, leading to a greater disturbance on the impacted film area. When the Weber number was doubled, the average wall heat flux could be enhanced by 36.3%. In addition, the heat flux could be boosted by 5.4% when the gravity load ranged from 0 to 1g. Moreover, a weightless condition suppressed the vapor escape rates on the heating wall where the volume fraction of the vapor on the wall could increase by 20% under 0g, leading to deteriorated heat transfer performance. The novelty in this paper lies in the accurate three-dimensional modeling of an aerospace-oriented droplet impacting two-phase heat transfer and fluid dynamics, associating macro-scale thermal performance to microscale thermophysics mechanisms. The findings of this study could guide the development of aerospace-borne spray cooling facilities for advanced aerospace thermal management.