Franklin Fact Archive
Back to Franklin Facts homepage.
Back to TV12
|THURSDAY, JUNE 15 - WHY DO FANS COOL YOU?
I've talked a lot this week about hot weather - now let's consider a way that
nature helps us beat the heat - the wind.
Air moving past your skin makes you feel more comfortable for the same reason
that wet clothes hanging outside dry faster on a windy day. It's all about
increasing the rate of evaporation. There's always water on your skin. And
some of that sweat is always evaporating. It takes energy to evaporate water,
and some of the energy comes from your body. So the evaporation of sweat
is a cooling process.
But as your sweat evaporates, the air right next to your skin becomes stocked
with water vapor. That crowding can slow the evaporation process, and thus slow
your cooling. But if the wind whisks away that sticky air next to your skin,
the road is paved for evaporation to pick up. And that means more cooling.
Keep that in mind the next time you're sitting in front of the electric fan.