ME395 Seminar 11/3; Evelyn Wang from MIT

[Beth Pruitt]

>Autumn 2011-2012
>
>Nanoengineered Surfaces: Transport Phenomena and Energy Applications
>
>Presented by
>
>
>
>Evelyn N. Wang
>Associate Professor of Mechanical Engineering
>Massachusetts Institute of Technology
>Thursday, November 3, 2011
>4:15 PM in Bldg. 380 room 380Y
>
>Nanoengineered surfaces offer new possibilities to manipulate 
>fluidic and thermal transport processes for a variety of 
>applications including lab-on-a-chip, thermal management, and energy 
>conversion systems. In particular, nanostructures on these surfaces 
>can be harnessed to achieve superhydrophilicity and 
>superhydrophobicity, as well as to control liquid spreading, droplet 
>wetting, and bubble dynamics. In this talk, I will discuss 
>fundamental studies of droplet and bubble behavior on nanoengineered 
>surfaces, and the effect of such fluid-structure interactions on 
>boiling and condensation heat transfer. Three-dimensional micro, 
>nano, and hierarchical structured arrays were fabricated to create 
>superhydrophilic and superhydrophobic surfaces with unique 
>properties. For example, with asymmetric superhydrophilic 
>nanopillars, uni-directional spreading of water droplets was 
>achieved where the liquid spreads only in the direction of the 
>pillar deflection. With hierarchical superhydrophobic surfaces that 
>mimic the superior non-wettability of a lotus leaf, water droplets 
>rebound at velocities greater than 4 m/s.  Energy-based models were 
>developed to explain and predict such behavior as functions of 
>pertinent parameters.  Furthermore, we investigated the effect of 
>nanostructure design to enhance heat transfer during pool boiling 
>and dropwise condensation. A critical heat flux of 196 W/cm2 with a 
>heat transfer coefficient greater than 80 kW/m2K was achieved during 
>pool boiling.  In addition, with stable dropwise condensation 
>surfaces, heat transfer enhancements of 4-6x were demonstrated with 
>partially suspended droplet morphologies. These studies provide 
>insights into the complex physical processes underlying 
>fluid-nanostructure interactions.  Furthermore, this work shows 
>significant potential for the development and integration of 
>nanoengineered surfaces to advance next generation energy systems.
>
>
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