Ultrathin Durable Organic Hydrophobic Coatings Enhancing Dropwise Condensation Heat Transfer

Area of Science:

• Materials Science
• Surface Chemistry
• Heat Transfer

Background:

• Organic hydrophobic layers are crucial for efficient dropwise condensation but often lack chemical and mechanical stability.
• Achieving a balance between ultrathin layers for low thermal resistance and robust durability is a significant challenge.

Purpose of the Study:

• To evaluate the long-term durability and heat-transfer performance of perfluorodecanethiol (PFDT) coatings.
• To compare PFDT against perfluorodecyltriethoxysilane (PFDTS) and perfluorodecyl acrylate (PFDA) coatings.
• To assess performance under demanding conditions, including high steam flow and pressure.

Main Methods:

• Fabrication and testing of PFDT, PFDTS, and PFDA coatings on copper substrates.
• Condensation heat transfer experiments under superheated steam flow (111 °C, 1.42 bar, up to 9 m s^-1).
• Durability assessment focusing on sustained dropwise condensation and hydrolytic stability.

Main Results:

• PFDT coatings significantly outperformed PFDTS in both heat transfer and durability.
• PFDT monolayers demonstrated superior durability compared to iCVD-fabricated PFDA coatings.
• PFDT maintained dropwise condensation for over 63 hours without degradation, exceeding PFDA's 30-hour lifespan.
• PFDT exhibited the lowest functionalization cost per area.

Conclusions:

• Perfluorodecanethiol (PFDT) coatings represent a highly durable and cost-effective solution for sustained dropwise condensation.
• PFDT's exceptional hydrolytic stability and performance under intense conditions make it ideal for practical heat transfer applications.
• The study highlights PFDT as a superior alternative to silane and acrylate coatings for enhancing condensation efficiency and longevity.