# Will hot object near ceiling vent create more draft?

As in the picture, we have a room with vents at the bottom to let cold air in and at the top to let hot air out. Normally the air flow is limited by the temperature gradient (correct me if I'm wrong). If we place a hot object in the vent on top, won't that create a faster draft? That way we could get very high "wind" speed indoors to replace fans.

Is this possible, and if yes, what's the limit for air flow per second?

• You need to do some calculations. Upward forces are a result of expansion of air and pressure from it being lower density. Some downward flow can also result from expansion but it will eventually cease at steady state since air needs to get there from somewhere (and it's probably not coming from above thanks to that density unless the chimney is ridiculously wide). It'd be a matter of how much the hot object cools by the time things get there.
– Abel
Sep 29, 2023 at 14:03
• isn't that exactly how a fireplace chimney works? Sep 29, 2023 at 17:35