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Delayed Frost Growth on Nanoporous Microstructured Surfaces Utilizing Jumping and Sweeping Condensates
Behrouz Mohammadian1, Rama Kishore Annavarapu1, Asif Raiyan1
1Department of Mechanical Industrial and Manufacturing Engineering (MIME), The University of Toledo, 4006 Nitschke Hall, Toledo, Ohio 43606, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 19, 2020
Summary
Self-propelled droplet jumping and sweeping on nanoporous vertically aligned carbon nanotube (VA-CNT) microstructures significantly reduce frost coverage and growth rates. Optimized microstructures enhance heat transfer and delay frost formation on supercooled surfaces.
Area of Science:
- Materials Science
- Surface Science
- Nanotechnology
Background:
- Self-propelled droplet jumping is crucial for efficient surface dew removal and frost growth delay.
- Supercooled surfaces require effective strategies to manage condensate and frost accumulation.
- Nanoporous vertically aligned carbon nanotube (VA-CNT) microstructures offer unique surface properties.
Purpose of the Study:
- To investigate droplet-jumping and droplet-sweeping phenomena on VA-CNT microstructures.
- To evaluate the impact of microstructures on frost coverage and growth rates.
- To explore methods for enhancing defrosting efficiency and managing frost formation.
Main Methods:
- Fabrication of VA-CNT microstructures on silicon substrates coated with poly-(1H, 1H, 2H, 2H-perfluorodecylacrylate) (pPFDA).
- Observation and analysis of droplet-jumping and droplet-sweeping phenomena under various conditions.
- Comparison of frost surface coverage and ice-bridging times using different microstructure geometries (line-shaped, hollow-cylindrical, cylindrical).
- Investigation of the effect of nonuniform roughness and droplet evaporation on frost dynamics.
Main Results:
- Droplet-jumping and droplet-sweeping phenomena were successfully demonstrated on pPFDA-coated VA-CNT microstructures.
- Closely spaced thin line-shaped and hollow-cylindrical microstructures were found to be optimal for reducing frost coverage.
- Nonuniform roughness enhanced jumping-associated droplet-sweeping on supercooled surfaces.
- Evaporation of frozen droplets near supercooled condensate droplets promoted Cassie-Baxter state frost growth and enhanced defrosting.
Conclusions:
- VA-CNT microstructures, particularly optimized geometries, effectively reduce frost coverage and growth rates.
- The combination of droplet-jumping and droplet-sweeping phenomena is key to improved frost management.
- Small inter-microstructure gaps facilitate dewetting transitions and Cassie-Baxter state frost formation, enhancing defrosting efficiency.
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