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Sub-micrometer dropwise condensation under superheated and rarefied vapor condition
Sushant Anand1, Sang Young Son
1Mechanical Engineering, School of Dynamic Systems, University of Cincinnati, Cincinnati, Ohio 45221, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 15, 2010
Summary
This study reveals that droplet growth rate slows as droplets enlarge on partially wet surfaces. A kinetic theory model supports interfacial mass transport as the primary growth mechanism, even for sub-microscopic droplets.
Area of Science:
- Thermodynamics
- Surface Science
- Fluid Dynamics
Background:
- Phase change on subcooled surfaces is common in nature.
- Droplet growth is influenced by surface properties like contact angle and system thermodynamics.
- Understanding droplet dynamics is crucial for various natural and industrial processes.
Purpose of the Study:
- To experimentally investigate the physics of droplet growth on partially wet surfaces.
- To analyze droplet size evolution over time during condensation.
- To explore the role of interfacial mass transport and nucleation in droplet growth.
Main Methods:
- Experimental condensation of superheated vapor on a subcooled silicon surface (contact angle 60°).
- Monitoring condensation using environmental scanning electron microscopy (ESEM) with sub-microscopic resolution.
- Analysis of isolated droplet growth kinetics before coalescence.
Main Results:
- Droplet growth rate decreases as droplet size increases, suggesting an underlying growth law.
- Experimental observations align with a theoretical model based on kinetic theory.
- Evidence of sub-microscopic droplet nucleation and growth between larger droplets was observed.
Conclusions:
- Interfacial mass transport directly on the condensing droplet surface is a key growth mechanism.
- The study provides insights into droplet growth dynamics on partially wetting surfaces.
- Sub-microscopic droplet formation plays a role in the overall condensation process.
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