The effect of a ceiling fan on air pressure in a room?

779 views
0

If flowing air has a lower pressure (Bernoulli’s Principle) then shouldn’t a ceiling fan decrease the pressure, causing external air to be pulled into a room via doors, vents, etc? How is this imbalance ultimately corrected? Air density?

In: Physics

Nope, you have a closed system. Whatever underpressure you get will have equal over pressure somewhere else.

The fan creates a slightly lower pressure above it and a slightly higher pressure below. These two generally balance themselves if in a sealed room, creating a cycle of circulation within the room. In a normal room with doors and windows, the pressure difference in parts of the room will cause the air to intermix with that outside the air more so than if the fan was not on, but the outgoing air is balanced by incoming air.

Yes, so right after you turn on the fan slightly more air will flow into the room than out of the room. After that, the pressure inside and outside will be equal, because the added density balances out against the lower pressure for its density because of the Bernoulli principle.

None of this is happening in any significant measure.