I am not sure why some hand dryers are blowing hot air and not just air at room temperature.
To me, hair dryers are just a way to dry one's hands using the same principle as when we shake our hands in the air, or when we blow some air over a hot drink.
Given that the blown air temperature's is not enough (is it ?) to vaporize water, why is hot air used?
Best Answer
Fact:
By increasing the air's temperature, one also increases the amount of water vapor it can hold before saturating.
Speculation:
Therefore, the osmotic pressure on water molecules in your hair increases and the water vaporizes more quickly than with room temperature air.