On the Individual Droplet Growth Modeling and Heat Transfer Analysis in Dropwise Condensation

The low convective coefficient at the 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 dependence 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 that 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 the effect of the 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 that incorporates surface tension, the Marangoni convection, and active mass transfer at the liquid-vapor interface, the 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 a contact angle of 150 degrees is observed. The effect of shape change due to gravity on the heat and mass transfer analyses of individual droplets found to be negligible.