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Liquid Distribution Problem - please help

  1. Nov 18, 2013 #1
    Liquid Distribution Problem -- please help

    Hello guys, I'm a mechanical engineer fresh out the college.
    I'm designing a liquid transferring device, and really really need some advice/help.

    So, my device right now has one 13mm diameter inlet that divides into twelve 4mm diameter “tubes” which are 77mm long, and the each tube have eight 3mm diameter outlets which are 9mm apart.
    Simply put, there is 1 big 13mm inlet that leads to 96 small 3mm outlets.

    My problem right now is that I don’t know where to start off to find the optimal inlet pressure/diameter as well as the optimal outlet diameter in order to transfer/distribute water throughout the device evenly. The outlet pressure doesn't matter for my application, but it just needs to dispense the water evenly throughout all the outlets.

    How could I approach this problem? Am I just missing a really simple point, or could it be a pretty tough problem? I’m thinking that the first thing that needs to be solved is the optimal pressure needed in order to push the water through 77mm “tube” all the way up to the last (8th) hole.

    Thank you so much for your time!

  2. jcsd
  3. Nov 18, 2013 #2
    Look up in the literature how to design "distribution manifolds." Most distribution manifolds involve gas, for which you can neglect viscous pressure variations. But, for water, you may also need to consider frictional pressure variations. You are basically dealing with a fluid mechanics problem.
  4. Nov 18, 2013 #3


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    The tubes are going to experience a pressure drop as the fluid leaks from the outlets, so to get uniform outflow, there needs to be larger outlets as the pressure drops. Also, it is often quite difficult to get flows to partition equally between a lot of little tubes. Not sure that this is easily modeled, it may take trial and error.

    Could the design be modified to have a plenum after the inlet sort of like a shower head to feed the 96 small outlets?
  5. Nov 18, 2013 #4
    Your use of the term plenum is the same as what I was referring to when I mentioned a distribution manifold. The basic concept in designing distribution manifolds is to make the pressure variations within the manifold small compared to the pressure drops through the outlet tubes. The pressure variations within the manifold can be determined by various approximations or by use of CFD. The pressure drops through the outlet tubes are easier to calculate. One just needs to make the manifold large enough so that the uniformity of flow through the outlets meets specifications.
  6. Nov 18, 2013 #5
    use a back press , this way make all outlet = . By placing a sized tip at the end of all the line .
  7. Nov 19, 2013 #6
    how long does the tip need to be? Or how long the tip need to be far apart from the wall (ceiling)?
  8. Nov 19, 2013 #7
    where could i find the literature...?
  9. Nov 19, 2013 #8
    i could, but im not quite sure how the plenum works. and wouldnt the outlets need to be smaller, not larger?

    Thank you.

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