Nucleation Dynamics for Water Condensation on Hydrophobic Surfaces in the Presence of Non-Condensable Gases
Date of Award
Master of Science (MS)
The density and rate of nucleation (here-in called nucleation density rate) significantly influences the heat transfer performance during dropwise condensation, as more than 70% of the total heat transfer happen for droplets smaller than 10 μm. Based on the classical nucleation theory, supersaturation strongly influences nucleation dynamics. However, the presence of non-condensable gas can strongly reduce the nucleation density rate by forming a vapor-depleted gas diffusion layer. Therefore, this work studied the relationship between nucleation density rate and supersaturation ratio during dropwise condensation on subcooled smooth hydrophobic surfaces with the presence of non-condensable gases in a custom-built condensation chamber. High-speed imaging and high-resolution microscopy enabled the experimental quantification of condensation dynamics. These were then compared to theoretical values based on the classical nucleation density. Based on the present experiments and a size distribution model, the relationship between heat transfer rate and supersaturation ratio were analyzed. Finally, through experimental observations, it is shown that the fast movement of relatively larger droplets can disturb the diffusion layer and enhance the nucleation density rate.
David Peters, Ramesh Agarwal
Permanent URL: https://doi.org/10.7936/b6j1-wf73