How condensation frosting depends on surface orientation and wettability

Presenter: Mohammad Swedat, Mechanical Engineering

Authors: M. Swedat, T. Jagdhari, G. Helm, M. Edalatpour, A. Staples, J. Boreyko

Abstract: Condensation frosting occurs when water vapor comes into contact with a chilled surface, condensing into droplets that freeze into ice. While surface chemistry and coatings have been widely studied to reduce frost adhesion, fewer studies have examined the fundamental mechanisms governing frost growth rates, especially the coupled effects of surface orientation and wettability remain poorly understood. In this work, we show that tilting a surface can alter frost growth rates by up to fourfold. This arises from distinct orientation-dependent regimes: convection-enhanced densification at 0°, convection-induced sweeping of the non-condensable gas barrier at 90°, and minimal growth at 45°, where neither dominates. Wettability further modulates frosts, particularly at 45°, where hydrophobic surfaces accumulate nearly twice as much frost as hydrophilic ones due to non-condensable gases getting trapped in interdroplet dry zones, reducing diffusive resistance. These findings reveal the coupled influence of geometry and chemistry on frost evolution, demonstrating that a simple tilt adjustment can effectively suppress frost formation.