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[DPRG] Computing back pressure in an exhaust system
Subject: [DPRG] Computing back pressure in an exhaust system
From: Chuck McManis
cmcmanis at mcmanis.com
Date: Wed Dec 5 21:21:25 CST 2007
At 07:07 PM 12/5/2007, Triffid Hunter wrote:
>On Wed, 5 Dec 2007, Chuck McManis wrote:
>
>>My current best idea is to build some tubing that connects from the
>>output of my Shop-Vac, has a way to put an exhaust system in the
>>middle of it and then a vertical tube with an indicator (probably a
>>ping pong ball) at the output.
>>The thought being that even if I couldn't calibrate it in SI units
>>I could at least get a comparison of the existing exhaust system
>>and my new one. I'm hoping that the ping pong ball going up to the
>>same level means that they have equivalent rates of flow, which
>>translates into equivalent back pressure.
>>
>>Any thoughts on this problem?
>>--Chuck
>
>Should work fine for a/b comparison, however you may need something
>heavier than a ping pong ball, and a tapered vertical pipe so the
>higher the ball goes, the more room there is around it, and the less
>pressure on the underside of the ball. A straight pipe will have the
>same pressure along its whole length, so as soon as the flow is
>enough to move the ball, it'll come out the top.
>
>A piece of mesh over the opening would also be wise, to catch the
>ball if it's too light ;)
Good idea on the Mesh, I've noted that one. Instead of tapering the
pipe (complex) perhaps drilling holes along its edge so that at each
level some of the air exits the side of the pipe ? I'm thinking that
would lower that static pressure past each set of holes by a fixed
amount. (and it would be way easier to build than trying to figure
out the taper!)
--Chuck
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