Understanding the effect of superhydrophobic coatings on energy reduction in anti-icing systems

In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication antennas to date, less attention is paid to coating strategies. The majority of studies dealing with coatings have focused mainly on reducing ice adhesion forces, to easily remove ice, once it has formed. In this study we focused on an alternative strategy that consists of promoting the shedding of liquid water as a way to reduce the total amount of water present on the surface that can freeze. Shedding of liquid from the surface can be enhanced by modification of surface wettability, by means of the application of superhydrophobic coatings, i.e. water repellent coatings, characterized by low water adhesion forces. To study the effect of superhydrophobic coatings on surfaces exposed to icing conditions, tests were performed in an open loop icing wind tunnel (IWT) on a standard NACA0021 airfoil in two different icing conditions. Three samples were used during the tests, each one is characterized by different wettability properties. To simulate the presence on anti/de-icing system, the wing was also equipped with an electrical heater, mounted at the inner side of the wing leading edge. Results from IWT tests demonstrated that surface wettability is an important controlling factor not only for reducing ice accretion on the wing, but also for reducing by up to 80% the energy required to avoid ice accretion on the wing. The findings from IWT tests as described, together with results from a previous work on drop shedding, reinforced the hypothesis that shedding of drops is the key controlling mechanism for an efficient icing mitigation strategy.