Anti-Icing Meter Scale Superhydrophobic Heat Exchangers

Frost formation on heat transfer equipment such as air-source heat pump evaporators can result in drastic efficiency penalties. The reduced performance arises due to the insulating nature of ice and the increase in fan power required to pump air through the constricted channels between frosted fins. Furthermore, the need to defrost adds appreciable energy usage to the system. Recently, researchers have developed many variations of superhydrophobic surfaces to demonstrate both thermodynamic and non-thermodynamic frost formation inhibition, often employing hard to scale fabrication techniques, costly manufacturing methods, and unrepresentative surface materials. Many of these studies have focused on frosting delay mechanisms governed by the efficient removal of condensate droplets prior to supercooling and freezing through surface-to-kinetic energy driven coalescence-induced droplet jumping. By developing a simple, scalable, and cost-effective method of coating nanostructured boehmitized aluminum with vapor deposition of a fluorinated silane, we were able to demonstrate frost formation inhibition on decimeter scale heat pump evaporators. Heating mode tests performed in a wind tunnel according to ANSI/AHRI Standard 210/240-2008 showed a 3X slower frost formation rate in cold and dry conditions when compared to regular uncoated or superhydrophilic heat exchangers due to enhanced condensate removal prior to supercooling and frost formation. This study not only provides key insights into the fabrication of highly scalable aluminum and copper based superhydrophobic coatings for meter scale heat exchangers, it serves as a design platform for nanoengineered coatings that can reduce condensation frosting.Air Conditioning and Refrigeration Center (ACRC)Ope