Development of a Durable Vapor Phase Deposited Superhydrophobic Coating for Steam Cycle Power Generation Condenser Tubes

The condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long lasting wetting inhibiting surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings appropriate for use on condenser tubes in steam cycle power generation systems may soon become a reality. This work presents a nano-scale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nano-particles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemi-cylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel condenser tube materials as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.