Enhancing condensation heat transfer and anti-frosting performance through robust surface engineering

Abstract

therefore, enhancing the condensation heat transfer performance can increase the overall system’s efficiency. Dropwise condensation induced by a superhydrophobic surface generally leads to improved performance compared to filmwise condensation by the frequent shedding of condensed droplets. Additionally, the superhydrophobic surface minimizes frost formation by rapidly removing droplets and inhibiting nucleation. However, finding a superhydrophobic surface with appropriate durability remains challenging owing to the harsh environment encountered by many condensers. In this thesis, we propose a robust ceria-based superhydrophobic surface for long-lasting dropwise condensation and anti-frosting, where the superhydrophobicity is induced by hydrocarbon adsorption on the surface due to ceria, not by coating itself. The surface characterization results indicate that rapid self-recovery of superhydrophobicity (~48 hours) is possible by incorporating polymeric binders as a hydrocarbon source. The developed surface can provide enhanced durability even after various harsh environmental conditions, including mechanical, chemical, and frosting damages. The heat transfer performance was 2~3x higher than the filmwise mode, and the enhanced performance was maintained over a prolonged period due to the sustainable dropwise mode compared to conventional hydrophobic coating. Furthermore, since the condensation frosting inevitably occurs at the heat exchanger, fully coated with the superhydrophobic surface, it was coated only at the edge to delay the frost propagation efficiently. Compared to the bare heat exchanger, the edge-coated heat exchanger provided a 67% decrease in air side pressure and an 18% increase in heat transfer rate. Our results suggest that the ceria-based superhydrophobic surface can promote long-lasting dropwise condensation and efficient frosting delay, facilitating effective heat transfer in practical applications where poor heat transfer performance is prevalent due to the filmwise mode.

Water vapor condensation and condensation-induced frosting occur frequently in diverse industrial fields