Dinner Questions

Question:
We showed before that a fan should heat up a room, so how does it keep us cool?

Hints:

• It's not by refrigeration or like an air conditioner (or at least the effect is negligible).
• In Canada everybody knows about the wind chill effect.
• Most people burn about at about 100 Watts. This heat must go somewhere.
  

Answer:

We create heat, but if there's no wind we heat the air close to our skin and it sticks around, slowly moving away from us (upwards). This air insulates us, makes it more difficult to remove the heat made by our body (it radiates some of the heat back into our body as well).
The fan pushes the hot moist air near our skin with cooler drier air from the room and makes us cooler.
If the room is really hot, we begin to sweat and the wind helps us evaporate this sweat. This evaporation removes even more heat from our body.
Having a fan on in the room when no one is in it, is not very useful and wastes energy.
On the other hand, if a room is hot and the outside air is cooler a fan near an open window can help cool the room more quickly. (I'm not sure which direction the fan should point - should it blow the cold air in, or blow the hot air out?).

Here's a good link about how a fan works.