Condensation Heat Transfer of Water Vapor on Microstructured Surfaces of Diverse Wettability

The primary objective of the study is to investigate steam condensation performance on a copper substrate featuring microstructured coatings of diverse morphology. The copper substrate was coated with microparticles of three different materials viz. tungsten carbide, chromium-nickel alloy, and aluminum oxide, using high velocity oxy-fuel thermal spray coating technique. The surface characterization of the tested samples was carried out by Stylus surface profilometer, Contact angle analyzer, scanning electron microscopy, together with energy dispersive x-ray analysis. Surface coating achieved with chromium-nickel alloy and aluminum oxide microparticles resulted in a hydrophilic surface, while the coating achieved with tungsten carbide microparticles was hydrophobic. The condensation performance of the uncoated and coated surfaces was evaluated and compared. Film condensation was observed on all surfaces, even on the hydrophobic surface. In the tested conditions, the film heat transfer coefficient improvement over the untreated surface was 100% to 120% for the hydrophobic tungsten carbide coating, 50% to 65% for the hydrophilic chromium nickel coating, and 20% to 30% for the hydrophilic aluminum oxide coating. The study demonstrates the potential application of thermal spray coating in improving the surface level mechanical properties as well as film condensation heat transfer performance.