Sizing a vent?

Velocity is easy, making assumptions that the air is not shearing near the boundary with the pipe.

450 CFM, and a 4" pipe. 4" = Pi 2^2 = 12.56 Sq In. or .087 Sq Ft. 450 / .087 = 5172 ft/min, or just about 60 MPH.

Jon

How long is the pipe? In the final analysis, its going to come down to pressure drop for most reasonable velocities.

Hi Paul,

The 4" hose is 10' and it vents to air as there are no particulates in the flow, it is just fume extraction. However the extractor is on the outside end if that makes a difference. It is so bloody noisy I am putting it outside.

Dave

Hi Jon,

Holy crap Batman, that is cranking along.

Thanks Jon

Dave

The noise and the small pipe and the high velocity all go together. Suction line (fan outside) is much less efficient than a pressure line (fan inside).

You need to c> >

"hose"? If you mean the hose that is a wire helix covered with cloth/vinyl, it will have a LOT more resistance than smooth pipe. E.g., aluminum clothes dryer exhaust pipe. Also, elbows add a lot to flow resistance: keep the run as direct as possible.

But, you knew all that, Bob