Xiaomin Wu

Investigation of the possibility of frost release from a cold surface

Abstract An experimental study has been conducted to investigate the possibility of causing frost to release from a cold surface. Both hydrophilic and hydrophobic surfaces were examined. Mechanical vibrations were attempted to release the frost from the hydrophobic surface. A thermoelectric cooler (TEC) was used to provide a cooling source for the frosting surface. A 40 mm square test sample of aluminum fin stock, 0.25 mm thickness, was attached on the cold side of the TEC with thermal grease. A uniform frost pattern was observed on the hydrophilic surface. However, the frost pattern on the hydrophobic surface was non-uniform and “pock-marked”. The frost on the hydrophobic surface could not be released by surface vibration. The melted frost (condensate) on the hydrophilic surface wetted the surface. However, the condensate existed as droplets on the hydrophobic surface. It appears that hydrophilic coatings should not be applied to the surfaces of evaporators that experience freezing condition, because when the frost melts, the fully wetted hydrophilic surface may act to retain condensate, which immediately re-freezes after defrosting. If the evaporator must operate under either freezing or non-freezing conditions, a hydrophilic coating is probably preferable.