Heat transfer rates for filmwise, dropwise, and superhydrophobic condensation on silicon substrates

Condensation, a two-phase heat transfer processes, is commonly utilized in industrial systems. Condensation heat transfer can be optimized by using surfaces in which dropwise condensation (DWC) occurs, and even further optimized using superhydrophobic surfaces. For superhydrophobic condensation, a structured silicon surface with pillars 2.1 p.m tall, 200 nm in diameter, and a 400 nm pitch was tested. By removing noncondensable gases (NCG) from the system by means of a steam trap, the heat transfer rates of DWC and SHC were found to be greater than that of filmwise condensation (FWC) by a factor of 2, but indistinguishable from each other. The effect of NCG leads to a 5x reduction in heat transfer rates for both DWC and SHC. DWC heat transfer rates are as much as 50 kW/m 2 less than FWC at the same temperature difference, representing a 25% reduction. However, the SHC heat transfer rates remain above those of FWC by as much as 50 kW/m² at the same temperature difference, representing a 20% improvement. These studies suggest that SHC may be a useful passive method to improve condensation heat transfer rates in the presence of NCG. However, it remains to be seen if SHC can provide better heat transfer rates than DWC under saturated steam conditions.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2011

Author dc:creator

• Hery, Travis M

Advisor dc:contributor.advisor

• Evelyn N. Wang.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/68842

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/68842