A microscopic visualization method was applied experimentally

where comparative observations of frosting processes were conductedunder the same conditionson bare aluminum and hydrophobic surface with contact angles of 78° and 141°

respectively. The hydrophilic surface with a contact angle of 26°

whose initial ice crystal shapes were observed and contrasted

was also included. Results showed that under the condition of low relative humidity at a surface temperature of ?10 ℃

the hydrophobic surface can delay frosting for 29 min in comparison with the bare aluminum surface. When the temperature decreased to ?18 ℃

the hydrophobic surface still demonstrated a satisfactory anti-frost effect. After an hour

the frost height on the surface of the hydrophobic surface was only 68% of the frost height on the bare aluminum surface. Furthermore

at the surface temperature of ?26 ℃

there were relatively large differences in the shapes of initial ice crystals for the three surfaces that had different contact angles. The hydrophobic surface tended to form denser dendritic frost crystals

which grew horizontally and transformed to plates

whereas the hydrophilic surface was inclined to form sparse needle-like crystals that grew in the vertical direction. As the water vapor in the air diffused into the frost crystals

then needle-crystals gradually transformed to sheet forms from top to bottom.