Microscopic observation of frost behaviors at the early stage of frost formation on hydrophobic surfaces

Microscopic seed behavior in the early stage of frost formation was experimentally observed with different fin surface contact angles from bare to superhydrophobicity under air-source heat pump operating conditions. The seed average height, radius, number, and frost density at the early stage of frost were analyzed. As the surface contact angle increased, the seed average height and number increased, while the seed radius and frost density decreased. A correlation with a Fourier number was proposed from the measured data. With the correlation, the large and small frost retardation effect regions were identified.