Heat transfer through a condensate droplet on hydrophobic and nanostructured superhydrophobic surfaces

Understanding the fundamental mechanisms governing vapor condensation on non-wetting surfaces is crucial to a wide range of energy and water applications. In this thesis, we reconcile classical droplet growth modeling barriers by utilizing two-dimensional axisymmetric numerical simulations to study individual droplet heat transfer on non-wetting surfaces (90° < θ_a < 170°). Incorporation of an appropriate convective boundary condition at the liquid vapor interface reveals that the majority of heat transfer occurs at the three phase contact line, where the local heat flux can be up to 4 orders of magnitude higher than at the droplet top. Droplet distribution theory is incorporated to show that previous modeling approaches under predict the overall heat transfer by as much as 300% for dropwise and jumping-droplet condensation. To verify our simulation results, we study condensed water droplet growth using optical and ESEM microscopy on bi-philic samples consisting of hydrophobic and nanostructured superhydrophobic regions, showing excellent agreement with the simulations for both constant base area and constant contact angle growth regimes. Our results demonstrate the importance of resolving local heat transfer effects for the fundamental understanding and high fidelity modeling of phase change heat transfer on non-wetting surfaces.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2016

Author dc:creator

• Chavan, Shreyas Atmaram

Contributors dc:contributor

• Miljkovic, Nenad

• Heat transfer
• condensation
• superhydrophobic surfaces
• jumping droplets
• non-condensable gases
• droplet growth

Statement dc:rights

• Copyright 2016 Shreyas Chavan

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/90829

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/90829