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Multichannel Square Tube Hydraulic Diameter

  1. Feb 6, 2007 #1
    Hello, I am new to this forum.

    I read the thread about the water flow in a rectangular tube because I wanted to correlate what was being said into my own problem.

    My question I believe is very simple:

    I have a rectangular tube that has inner dividers, let's say that my tube has 6 channels inside that are 7.15mm L X 3.54mm W, plus a 7th channel 7.15mm L X 5mm W.

    Lets's say also that if I neglect the inner walls, the result is a bigger rectangle, roughly 29.3mm L x 7.15mm W.

    I need to come up with the Hydraulic Diameter for the whole tube.

    What is the approach I should take:

    a) should I add the seven Hydraulic Diameters for each inner tube?

    b) should I neglect the inner walls and calculate for the whole tube?

    When I add up each channel's HDs, the results is 3 times higher than when I calculate for the whole tube, neglecting the inner walls.

    I would really like your input on this subject, and I am sorry if this is so simple I had overlooked the answer.

  2. jcsd
  3. Feb 7, 2007 #2


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    hi chup
    That won't work, you'll get an enormous equivalent pipe diameter.

    That won't work either. The inner walls create frictional pressure drop that you'd be neglecting.

    The only way I know of to do this is to treat all seven diameters as independant flow paths.
  4. Feb 9, 2007 #3
    Q_Goest: Thank you, that seems to be the most logical approach.
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