Researchers have developed a polymer coating that helps condensation droplets form and shed faster, potentially improving heat transfer by up to 5.5 times compared with plain copper surfaces.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed a polymer coating that improves how water droplets form and detach from a surface during condensation, achieving up to 5.5 times the heat transfer performance of conventional copper. The work was led by Professor Youngsuk Nam of the Department of Mechanical Engineering and Professor Sung Gap Im of the Department of Chemical and Biomolecular Engineering.
Condensation occurs when water vapour changes back into liquid and is an important part of processes such as steam-cycle power generation, desalination and some thermal-management systems. On a conventional metal surface, droplets tend to merge into a continuous water film, which adds thermal resistance and slows heat transfer. Dropwise condensation takes a different approach: individual droplets form, grow and detach from the surface, exposing fresh areas for further condensation and allowing heat to move away more efficiently.
The challenge is maintaining this process on a practical surface. Rough surfaces provide more locations for droplets to form but can also hold them in place, while smoother surfaces help droplets detach but provide fewer nucleation sites. The KAIST team addressed these two problems separately by controlling the structure of an ultrathin polymer film. Using initiated chemical vapour deposition (iCVD), the researchers found that thinner films produced denser nanoscale polymer aggregates, creating about three times more nucleation sites than thicker films. A subsequent heat-treatment step weakened the interaction between the droplets and the surface, allowing them to detach before becoming too large.
Tests on copper tubes similar to those used in condenser systems produced a peak condensation heat transfer coefficient of about 88 kW·m⁻²·K⁻¹. This was around 5.5 times higher than a conventional copper surface with film condensation and more than 50 per cent higher than the hydrophobic coating used as a comparison.
Hydrophobic coatings are commonly used to encourage dropwise condensation by repelling water, but they do not directly control how quickly droplets leave the surface. The KAIST approach combines a high density of droplet nucleation sites with easier detachment. The iCVD process can also produce ultrathin, uniform films over complex shapes, which could be useful for coating existing condenser tubes rather than requiring completely redesigned heat exchangers.
The work remains laboratory-validated coating technology rather than a commercial product. The researchers demonstrated the approach on copper tubes under controlled condensation conditions, but the published study does not show the coating operating on full-scale condenser tube bundles in a power plant or desalination facility. The study reports four weeks of stable performance for the thin coatings, while longer-term durability under industrial operating conditions still needs to be demonstrated. The researchers therefore present the work as a basis for future scale-up and extended testing rather than a ready-to-deploy industrial coating.
India has large-scale applications for this type of condensation technology. Coal- and gas-fired power plants use steam condensers to turn exhaust steam back into feedwater, while desalination facilities provide another potential application where thermal management affects energy consumption. Tamil Nadu, for example, operates large seawater desalination facilities, including a 150 MLD plant at Nemmeli. The reported improvement was demonstrated at the surface and copper-tube level, so its effect on the overall energy consumption of power plants or desalination facilities would need to be established through larger-scale testing. Similar improvements could eventually benefit cooling and thermal-management systems used across India’s growing electronics and industrial infrastructure.
The central idea behind the research is simple: a surface feature once treated as a defect can be deliberately controlled to improve condensation. The reported 5.5-times improvement at the copper-tube level shows the potential of the approach, but its impact on real-world energy consumption will depend on how well the coating scales and survives long-term operation.
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