Abstract
The wetting of solids by liquids is an important consideration for heat exchangers as it can have a dramatic impact on heat transfer efficiency. The use of superhygrophobic materials, surfaces or coatings is expected to give rise to next-generation high efficiency heat exchanger designs, and this is particularly the case for geothermal heat exchangers where heat exchanger materials interact with highly corrosive fluids.
In order to address this challenge, a material-by-design approach has been adopted, where nanoscale metal oxides were designed and fabricated to provide improvements to the performance of conventional hygrophobic coatings, as well as bare base materials. Novel superhygrophobic coatings were developed, consisting of a polysiloxane matrix, which provides an inherently water repellent film, and functionalized silica nanoparticles, providing bottom-up roughness. Coatings were applied to aluminum Q-panels, which had top-down engineered roughness, providing a composite structure with dual-scale roughness, necessary for superhygrophobicity. The introduction of coatings with multiple functionalities has resulted in the development of both mechanically resilient and highly repellent coatings for heat transfer applications. The novel coatings survived under prolonged immersion in an acidic water solution without changing their superhygrophobic properties, demonstrating their potential for heat exchanger applications and other applications involving moderately corrosive environments.
