On the individual droplet growth modeling and heat transfer analysis in dropwise condensation

Abstract

The low convective coefficient at condenser part of spreaders and vapor chambers due to film blanket blocking encourages utilizing dropwise condensation (DWC). Challenges exist in the experimental characterization of DWC, which includes dependency on numerous parameters and more importantly measurement difficulties due to low driving temperature differences. This highlights the necessity of accurate modeling of this complex process. The widely used macroscale modeling process of DWC, known as classical analytical modeling of DWC, typically combines state of the art droplet size distribution model with a simplified shape-factor based heat transfer analysis of a single droplet which contains major simplifications such as conduction-only through the bulk liquid, hemispheric droplet shape, and homogeneously distributed temperature over the entire droplet surface. Recent numerical approaches included effect of Marangoni convection and implanted realistic thermal boundary conditions on liquid-vapor interface and reported significant errors of classical modeling. Based on a novel dynamic numerical approach which incorporates surface tension, Marangoni convection, and active mass transfer at the liquid-vapor interface, droplet growth phenomenon has been modeled in this study. Notable differences of droplet growth and flow field have been observed resulted from dynamic growth modeling of the droplet as more than 70% heat transfer rate underestimation of quasi steady modeling in 1 mm droplets with contact angle of 150° is observed. Effect of shape change due to gravity on the heat and mass transfer analysis of individual droplets found to be negligible.