In order to study the phenomenon of the frost melt water retention on fin surfaces of the air source heat pump during the defrosting process

the mechanism of the frost melt water retention was researched by theoretical analysis

and a frosting-defrosting experimental system was developed to study the frost melt water retention on four fin samples with different surface characteristics. Experimental results showed that there was obvious difference on retained water distribution between different fin surfaces: retained water formed a thin water film on the hydrophilic surface while only a few spherical droplets with small sizes stayed on the super hydrophobic surface. The retained water mass decreased with the increase of contact angle hysteresis

which on the super hydrophobic surface decreased by 79.82% compared with that on the hydrophilic surface. The frosting degree had a significant effect on the frost melt water retention of the bare surface while had no effect on that of the super hydrophobic surface. However

changing the defrosting temperature almost had no effect on the frost melt water retention of fin surfaces.