Experimental study of hybrid anti-icing systems combining thermoelectric and hydrophobic coatings

Two commercial hydrophobic coatings: StaClean™ with a water droplet contact angle of 101°and Wearlon® Super F1-Ice with a contact angle of 115°and one superhydrophobic coating: HIREC 1450 with a contact angle of 152° were studied combined with a thermoelectric anti-icing system under icing conditions. All coatings and the reference surface were tested under glaze and rime ice. The deicing tests were conducted in the Anti-icing Materials International Laboratory's (AMIL) low speed closed loop Icing Wind Tunnel with 0.4 g/m3 liquid water content, a 26.7 ± 2.6 μm water droplet median volumetric diameter, 21 ± 0.5 m/s air speed and temperatures of -5 and -20 ± 0.5°C. For these tests, a 4′ chord NACA 63-415 airfoil 2D blade box-section of 10′ covered with a thin aluminum sheet protected at the leading edge and on the bottom by a thermoelectric anti-icing system composed of two ′ × 10′ heating elements with a power density of 40 W/in2, was used. The superhydrophobic coating showed excellent results with a power reduction of 13% for rime ice and 33% for glaze ice. Hydrophobic coatings performed at a lower level than the superhydrophobic coatings with a power reduction of about 8% for rime ice and 13% for glaze ice, but their effect was still significant. Also, the coatings significantly improved the runback water, most probably due to their hydrophobic nature. For the superhydrophobic coating, the surface was mostly free of ice due to the fact that drops roll over the surface to the trailing edge and for hydrophobic coatings, the runback back water froze outside the protected area; with time, a barrier developed which stopped runback water and ice accumulation increased with time. For rime and glaze ice accretion, the higher the contact angle, the more effective the coating; which suggests that a superhydrophobic surface with a high contact angle could significantly reduce the anti-icing power required