Most homes have several such vents for exhaust fans and the clothes dryer. As the air exhausts it swings the vanes upward from their seated position. Something has to provide this force and obviously it is the movement of the exhausted air. I suppose each vane may benefit from an airfoil effect also, i.e. the flow of the air over the top of each vane may create a lower pressure and help pull the vane upwards. The vanes do not typically open all the way which would be a 90 degree swing. Looking at my exhaust vent in operation I guess around 75 degrees. So this leads to the question:
If I pinned the vanes in that 75 degree position thus eliminating the necessity for the air to provide any force, does this result in increased airflow, lower pressure drop, whatever?
It also allow a steady inflow of unconditioned air into the house. Whether it’s hot humid air while you’re running the AC or cold dry air during winter.
I notice this often with my dryer. If my clothes are left in the dryer overnight (which they always are), they’re freezing cold in winter (no big deal) and in summer they tend to get a bit damp from the humidity. I ended up installing a new vent that prevents that.
In any case, there’s no reason to concern yourself with propping those open. The force required to push them open is negligible. If a little bathroom fan with 15 feet of flex tubing attached to it can push it open, your dryer really isn’t going to have a problem.
Dunno. But it’s interesting to observe that the energy lost in the air flow is the friction and turbulence that it takes hold the vent in position – not the energy required to push the flaps up. Pushing the flaps up is a one-time event, like putting a book on a table.