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Thread: Under Floor Dust Collection

  1. #16
    Join Date
    Feb 2007
    Location
    N.E. coastal, U.S.
    Posts
    158
    "Flow testing done in Australia that shows long curves flow worse than short curves"?..

    Agreed, that statement is bound to be highly controversial. Chris, could you kindly provide some science and further documentation behind that assertion? Not only does it go against what "seems logical"; you're also implying that nearly two centuries of scientific research into fluid mechanics and our resulting textbooks on fluid mechanics and fluid dynamics that we learned from at university were wrong... Surely there has got to be another explanation to whatever might have been empirically observed. The flow coefficient of two 45 degree fittings back-to-back and added together always is better than a single 90 of equivalent radius and the longer the curve radius getting from vector A to right angle vector B, the better the flow coefficient, remains my thinking until proven otherwise. Simple conservation of momentum and energy, even within a fluid media of mixed densities .
    Last edited by Morey St. Denis; Today at 1:20 PM.

  2. #17
    Join Date
    Aug 2009
    Location
    Colorado Springs
    Posts
    34
    I think my underfloor duct question is about to get derailed....

  3. #18
    Join Date
    Jun 2017
    Location
    Saskatoon, Saskatchewan, Canada
    Posts
    421
    Morey here is a link with engineering data for air handling systems. On page 54 the duct losses for ninety degree and three piece ninety (i.e. two forty-five's) degree elbows are shown. The 3 piece ninety is almost double that of the smooth ninety degree elbows. Does it challenge your thinking? Even if you take in the value of the two forty-fives added together and not counting the straight section between they only best the smooth ninety with a .75R.

  4. #19
    Join Date
    Jun 2017
    Location
    Saskatoon, Saskatchewan, Canada
    Posts
    421
    Quote Originally Posted by Jon Snider View Post
    I think my underfloor duct question is about to get derailed....
    Maybe a little. Sorry.

    If I had a crawlspace and a strong floor I'd put the ducts below. Any future changes would be only a little harder in sitting room rather than from a ladder. You would just have to plug the old floor holes.
    Last edited by Peter Christensen; Today at 1:54 PM.

  5. #20
    Join Date
    Feb 2018
    Location
    Peoria, AZ
    Posts
    336
    "Flow testing done in Australia that shows long curves flow worse than short curves"?..
    The curve was upside down.

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