Why can ceiling fans spin so the air goes up? What would that benefit?



Why can ceiling fans spin so the air goes up? What would that benefit?

In: Physics

Hot air rises, so in the winter they will push the warm air from the ceiling down into the room.

Well if the air flows up then the heat will get pushed to the bottom of the room while the cold air gets lifted to the top 🙂

Your body is warmer than the air around it (usually). This means that the air around your body will be warmed by it. So the air around your body will be warmer than the air not near your body. When you turn on a fan, then the air in the room moves more. If it moves more, than it doesnt stay near your body as long, so your body is surrounded by cooler air.

Fan Blades are slightly tilted, or supposed to be. If it’s spinning in one direction the air is pushed up, following the curve. If it goes the other way, it goes down with the curve.

This helps push hot air down or cold air up to increase it’s efficiency in changing the temperature.

The air in the room will be mixed regardless of if the fan blows the air up or down. However, in winter you don’t want a breeze blowing directly on you as that would make you feel cooler. In summer, that’s exactly what you want, which has the added benefit of allowing you to run your AC a little bit less).


PS, remember, a fan (be it a ceiling, floor or desk fan) only cools YOU, it doesn’t create cold air (like an AC), in fact, it *technically* heats the room. In other words, leaving a fan running all day won’t mean you get to walk into a cool house when you get home from work. It might feel cooler due to the breeze and the air being well mixed instead of stratified. But you’re better off waiting until you get home to turn it on.

Also, one downside of having the air blowing up, is that it makes your ceiling dirty. Other than that, I generally prefer not having a fan blowing directly on me.

Either direction that a fan turns creates air movement in the room.

The difference is that, when the fan is pushing down, directly under it will be a burst of air. This can be useful in warmer months, but unwanted in the cooler months.

In either case, there is a current that goes between the fan, across the ceiling, down the walls, across the floor, and back up. It’s just a matter of which direction it’s going.

For ceiling fans you want them blowing air downwards in the summer time and pulling air upwards in the winter. It has to do with temperature gradients in the air as you move from floor to ceiling, primary heat transfer methods during those times of year, and your body temperature relative to the air that’s being moved by the fans.

In the summer when it’s hot, you want the fans to push air down towards you to cause a breeze that helps you feel cooler.

In the winter when it’s cold you don’t want a breeze but also the warmer air is rising towards the ceiling. You want the fans to pull the cool air up towards the ceiling to mix and push the warm air back down towards the ground. This will help to distribute the warmer air near you ceiling back into the rest of the room.