ME395 Seminar 11/3; Evelyn Wang from MIT

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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