Micro-observation of frost formation and deposition processes on a vertical hydrophobic cold surface was made under free convection conditions. The formation and shape variation of frost crystals during the initial period are described and the frost thickness variation with time on both hydrophobic and plain copper cold surfaces are presented. The various influencing factors are discussed in depth. The mechanism of frost formation on hydrophobic surfaces was analyzed theoretically. This revealed that increasing the contact angle can increase the potential barrier and restrain crystal nucleation and growth and thus frost deposition. The experimental results show that the initial water drops formed on a hydrophobic surface are smaller in size and remain in the liquid state for a longer time compared with ones formed on a plain copper surface. It is also observed that the frost layer deposited on a hydrophobic surface is loose and weak. Though the hydrophobic surface can retard frost formation to a certain extent and causes a looser frost layer, our experimental results show that it does not depress the growth of the frost layer.

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