Dynamic behavior and heat transfer characteristics of a droplet impacting on the micro corrugated tube

Abstract

Liquid droplets impacting on rough or structured surfaces occur ubiquitously in nature and are applicable in many industrial activities. In this study, a 3-D numerical method has been selected to explore the dynamic behavior and heat transfer characteristics of an individual droplet impacting on the micro corrugated tube. The differences in dynamic behavior and heat transfer characteristics between single droplet impacting on a micro corrugated tube and a smooth circular tube were compared. Besides, how impact velocity and wettability affect hydrodynamics and heat transfer was studied. It turns out that the liquid film morphology, spreading length and liquid film contact area on the micro corrugated tube differ from those on the smooth circular tube due to the corrugations’ inhibition and anisotropy of the cylindrical surface. Furthermore, a considerably larger heat transfer coefficient is recognized within the former, owing to the greatly smaller liquid film contact area and larger liquid film average temperature on the micro corrugated surface than those on the smooth circular surface. As impact velocity rises, the global heat flow increases and finally remains unchanged on the micro corrugated tube and the smooth circular tube. With a growing surface hydrophobicity, structures (rough or smooth surfaces) play a less important role in affecting the droplet's morphology variation, and the heat transfer coefficient is barely affected, but the tendency to decline occurs in the global heat flow. This study can enrich and develop the dynamics and heat transfer theory of droplets impacting on rough surfaces and provide guidance for engineering applications such as spray cooling and anti-icing etc.