* Increased Evaporation: The primary reason for faster drying is that a fan increases the rate of evaporation. Evaporation is the process where water turns from a liquid to a gas (water vapor). When water evaporates from your hair, it takes heat with it (this is called "latent heat of vaporization"), which cools your hair down.
* Removing Saturated Air: Near the surface of your wet hair, the air becomes saturated with water vapor. This means the air is holding as much moisture as it can. The rate of evaporation slows down because there's less "room" for more water to turn into vapor. A fan blows away this saturated air and replaces it with drier air, allowing more water to evaporate.
* Increasing Airflow: The fan provides a constant flow of air, which continuously sweeps away the water vapor molecules, maintaining a concentration gradient that favors evaporation.
* Convection: The moving air from the fan also increases convection. Convection is the transfer of heat through the movement of fluids (in this case, air). The warmer air can carry more water, speeding the drying process.
In simpler terms:
The fan blows away the humid air around your hair, making room for more water to evaporate and turn into vapor. The constant air flow ensures more moisture can leave your hair quickly.