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Impeding liquid flow

  1. Apr 1, 2009 #1
    I need to lower the pressure of a 9.5 liter/minute stream of water flowing through a 3.17 mm passage 275 bar. I have a 22mm X 100 mm cylindrical volume in which to contain a single part or assembly of parts in which to accomplish this. I need to keep minimum ID to 3.17 mm. Heat generation is not a problem.

    I think I need to accumulate 510 “Lohms”. Lohms seem difficult to amass passing such a low rate of fluid through a series of 3.17 mm orifices. Best I gather is manipulating the liquid’s mass and inertia in an efficient flow pattern to remove it’s energy is the key to my problem. I only have hazy daydream like images of how this could be accomplished. I can’t justify the expense of trying out my whims through trial and error. I’ve put off this problem while designing the rest of the system hoping the solution would come to me in some kind of epiphany, but it hasn’t. Thanks for any help.
     
  2. jcsd
  3. Apr 1, 2009 #2

    Q_Goest

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    Hi Charlie. Industry doesn't generally use lohms, nor does academia. You've provided flow and upstream pressure, but not downstream pressure. If you can explain better what you need to accomplish that would help.

    I take it your minimum orifice size (3.17 mm) is due to solids going through?

    Also, is this ambient temp? Without looking, I'd guess you're in the supercritical range for water here.
     
  4. Apr 1, 2009 #3
    The Lee Company uses LOHM and calls it LOHM LAWS. There web site is here:
    http://www.theleeco.com/LEEWEB2.NSF/Engineering!OpenView [Broken]
     
    Last edited by a moderator: May 4, 2017
  5. Apr 1, 2009 #4
    Goest,
    The pressure drop of the power fluid will be an anticipated 4800 down to about 800 relative to ambient pressure. But ambient pressure will be up to 10000 psi so everything will stay liquid. Environmental temperature will be 100 to 250 F.
    I want to create the pressure drop in order to utilize the high pressure to operate a piston motor. Yes, it's a potentially trashy power fluid. I can't use valves or tiny orifices. I've operated the motor using orifices in testing it, but know it wouldn't be practical trying to operate it in it's intended environment.
    I picked up that "Lohms" at the site Nucleus refers to above. I thought I was making some headway on this using a pressure drop calculator from engineeringtoolbox. But then I noticed when I doubled the length of a passage, like from three inches to six, the pressure doubled. I knew then that it was worthless. But thanks for any help.
     
  6. Apr 2, 2009 #5

    Q_Goest

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    I've seen the lohm law stuff about 20 years ago but never saw anyone actually use it. I suppose someone does but it's unusual.

    The standard in industry has become the Crane Paper #410. You can purchase it online here:
    http://www.flowoffluids.com/tp410.htm [Broken]

    If you want to get started looking at this, another paper is from Pipe-Flo Pro which I've posted here:
    https://www.physicsforums.com/showthread.php?t=179830

    If you're looking to calculate water flow through an orifice, try API 520, para 3.8.
     
    Last edited by a moderator: May 4, 2017
  7. Apr 3, 2009 #6
    Goest,
    These plumbing and pipeline calculation programs seem to go by a different set of rules than higher pressure and velocity and smaller and shorter passage power transmission hydraulics. I don't trust the conclusions they draw when operating in the ranges I'm needing.
     
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