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.

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