Ultrahigh Subcooling Dropwise Condensation Heat Transfer on Slippery Liquid-like Monolayer Grafted Surfaces.

Area of Science:

• Materials Science
• Surface Chemistry
• Heat Transfer

Background:

• Rapid droplet shedding is vital for thermal management and water harvesting.
• Superhydrophobic surfaces face droplet pinning issues at high subcooling temperatures.
• Slippery liquid-like surfaces offer enhanced stability and low adhesion due to dense, smooth polymer chains.

Purpose of the Study:

• To develop and characterize slippery liquid-like surfaces for efficient dropwise condensation.
• To investigate the droplet shedding behavior and heat transfer performance at ultrahigh subcooling.
• To evaluate the long-term durability of these surfaces under condensation conditions.

Main Methods:

• Covalent bonding of linear poly(dimethylsiloxane) chains onto silicon substrates.
• Characterization of monolayer formation using cryogenic transmission electron microscopy.
• Measurement of condensation heat flux and heat transfer coefficient at various subcooling temperatures.
• Analysis of droplet distribution using macroscopic observations and environmental scanning electron microscopy.

Main Results:

• Achieved continuous dropwise condensation at ultrahigh subcooling temperatures (60 K).
• Reported high condensation heat flux (1392.60 kW·m⁻²) and heat transfer coefficient (23.21 kW·m⁻²·K⁻¹).
• Demonstrated excellent durability with only a 20.3% decrease in heat transfer coefficient after 100 hours.

Conclusions:

• Slippery liquid-like surfaces effectively promote droplet shedding and sustain dropwise condensation at high subcooling.
• These surfaces address challenges in heat transfer performance and durability for applications like thermal management.
• The low frictional forces of the polymer chains are key to preventing flooding and enhancing performance.