Condensation and Mobility Studies of Fluid Interfaces

Condensation is of central importance in a broad range of areas in nature and industry. Aerosol-cloud interactions, a currently a significant open question in climate modeling, and water harvesting mechanisms on organisms such as cacti, beetles, and spiders, are natural processes that are rely on condensation. Condensation is an effective method for transferring heat due to the latent heat required for a fluid to change phase from a gas to a liquid. Improvements in condensation processes would have an impact in a variety of industrial areas such as thermal management, environmental control, microelectronics, desalination, and power generation. Dropwise condensation is preferable over filmwise condensation because it has a significantly higher heat transfer coefficient. Nanopatterned surfaces are of interest because they have experimentally demonstrated higher heat transfer than their smooth counterparts, but recent heat transfer measurements on individual droplets have revealed discrepancies between theoretical predictions and experimental measurements for the smallest droplets. Interfacial properties on small length scales are often difficult to measure experimentally and are often used as fitting parameters in condensation models. The common assumptions used when modeling dropwise condensation are that (1) the condensing droplets are thermodynamically quasi-static and that (2) the heat and mass transport are uncoupled, that is, droplet motion and heat transfer are modeled independently of one another. In this dissertation, several continuum properties including the mass accommodation coefficient and interfacial mobility are computed allowing for the physical parameters to be known a priori for continuum scale models such as the Navier-Stokes-CahnHilliard equations or interfacial resistances in condensation models. Furthermore, the two fundamental assumptions used in condensation models are examined in an attempt to resolve the theoretical and experimental discrepancies. This will be done by leveraging microscopic and nonequilibrium thermodynamic approaches to determine the validity of the condensation assumptions for planar and highly curved systems. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Mechanical Engineering & Applied Mechanics First Advisor Jennifer R. Lukes Subject Categories Mechanical Engineering This dissertation is available at ScholarlyCommons: https://repository.upenn. edu/edissertations/3091 CONDENSATION AND MOBILITY STUDIES OF FLUID INTERFACES Paul L. Barclay A DISSERTATION in Mechanical Engineering and Applied Mechanics Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2018 Supervisor of Dissertation: Dr. Jennifer R. Lukes Professor, Mechanical Engineering and Applied Mechanics Graduate Group Chairperson: Dr. Kevin Turner Professor, Mechanical Engineering and Applied Mechanics Dissertation Committee: Dr. Portonovo S. Ayyaswamy, Asa Whitney Professor of Dynamical Engineering, Mechanical Engineering and Applied Mechanics Dr. John L. Bassani, Richard H. and S. L. Gabel Professor, Mechanical Engineering and Applied Mechanics Dr. Ravi Radhakrishnan, Professor, Bioengineering For my dad, mom, brother, and sisters.