The Use of Organic Coatings to Promote Dropwise Condensation of Steam

Fourteen polymer coatings were evaluated for their ability to promote and sustain dropwise condensation of steam. Nine of the coatings employed a fluoropolymer as a major constituent; four employed hydrocarbons and one a silicone. Each coating was applied to 25-mm-square by approximately 1-mm-thick...

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Bibliographic Details
Published in:Journal of heat transfer 1987-08, Vol.109 (3), p.768-774
Main Authors: Holden, K. M, Wanniarachchi, A. S, Marto, P. J, Boone, D. H, Rose, J. W
Format: Article
Language:English
Subjects:
420400 - Engineering- Heat Transfer & Fluid Flow
ALLOYS
BRASS
COATINGS
COPPER
COPPER ALLOYS
COPPER BASE ALLOYS
DROPWISE CONDENSATION
ELEMENTS
ENERGY TRANSFER
ENGINEERING
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
HEAT TRANSFER
Heat transfer in inhomogeneous media, in porous media, and through interfaces
HYDROCARBONS
METALS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PERFORMANCE TESTING
Physics
POLYMERS
SEMIMETALS
SILICON
STEAM
TESTING
TITANIUM
TRANSITION ELEMENTS
VAPOR CONDENSATION
ZINC ALLOYS
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Summary:Fourteen polymer coatings were evaluated for their ability to promote and sustain dropwise condensation of steam. Nine of the coatings employed a fluoropolymer as a major constituent; four employed hydrocarbons and one a silicone. Each coating was applied to 25-mm-square by approximately 1-mm-thick metal substrates of brass, copper, copper–nickel, and titanium. While exposed to steam at atmospheric pressure, each coating was visually evaluated for its ability to promote dropwise condensation. Observations were also conducted over a period of 22,000 hr. Hardness and adhesion tests were performed on selected specimens. On the basis of sustained performance, six coatings were selected for application to the outside of 19-mm-dia copper tubes in order to perform a heat transfer evaluation. These tubes were mounted horizontally in a separate apparatus through which steam flowed vertically downward. Steam-side heat transfer coefficients were inferred from overall measurements. Test results indicate that the steam-side heat transfer coefficient can be increased by a factor of five to eight through the use of polymer coatings to promote dropwise condensation.
ISSN:0022-1481
1528-8943
DOI:10.1115/1.3248156