I learned that it is more difficult to condense on a hydrophobic surface than on a hydrophilic surface. "More difficult to condense" means condensation has a higher energy barrier and more difficult to take place. However, what does it actually mean? Does it mean that a higher level of subcooling (lower temperature) is needed to condense on hydrophobic surfaces? However, I also learned that the dew point is only related to the temperature and the relative humidity but not the surface property. I would really appreciate if anybody can explain this confliction to me.
Zhaohui Li
Film condensation occurs on a hydrophilic surface that is wetted by water. The film closes the metal tubes of the condenser and the exchange deteriorates. Drop condensation occurs on the hydrophobic surfaces of tubes coated with graphene. On such surfaces there are more open places for heat transfer and therefore it is sometimes 4 times better than with film condensation. Therefore, hydrophobicity/hydrophilicity affects the droplet shape. On the hydrophobic one it is in the form of a ball, and on the hydrophilic one it is in the form of a film. This is due to the wettability, contact angle.
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