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The Equation for Volumetric Flow Rate?

  1. Nov 27, 2012 #1
    I'm not sure how to clearly express my query, so I'll round up the gist of it. I understand that this is an entry level question.

    I was told that, in order to calculate Volume Flow Rate (VFR), I would use these equations:

    * Q = Velocity * Area [EQUATION 1]
    * Q = Volume / Time [EQUATION 2]
    Units: m^3 / s

    ^Do I use both equations? Are they both deemed correct or only one and which one?
    ^Can you give an example problem or scenario in which I would use the appropriate equation?
    Last edited: Nov 27, 2012
  2. jcsd
  3. Nov 27, 2012 #2
    Example: You have a pipe with a diameter of 400mm. Water flows through the pipe at a velocity of 1 m/s. Determine how many liters you would have collected in a minute?

    Use your equation as you mentioned and come up with a solution, don't et sidetracked by the units, do the first principals correctly...
  4. Nov 27, 2012 #3
    @WillemBouwer Correct?

    Prompt: A pipe has a diameter of .4 meters. Water flows through the pipe at 1 m/s. Determine how many liters (water) you would have collected in a minute?

    Radius: .2 meters (m)
    Vinitial: 1 m/s
    Volume: ?
    Time: 60 seconds

    Q = V * A
    Q = 1 * (∏(.22))
    Q = 0 .1256637061 m3/s

    --> Q = V / T
    .1256637061 = V / 60
    Volume = 7.539822369 m3 or
    7.539822369 * 1000 = 7,539.822369 L

    1 m3 = 1000 Liters (L)
    Last edited: Nov 27, 2012
  5. Nov 27, 2012 #4
    There you go... Using the equation right...
    The second equation is just an explaining of the units or terminology, Volume flowrate is exactly that, m^3/s, volume over time. But the first equation is the most commonly used.

    However when you get a question, make sure to answer the question as asked with units, always remember your units... But you understand the principal! Cool beans...

    So, how many liters per minute?
  6. Nov 27, 2012 #5
    It should be on there.
    7,539.822369 L ?
    Thank you very much Mr. Bouwer. (:
  7. Nov 27, 2012 #6
    No problem. I see it shows now, didn't the previous one, haha. good job though, correct answer...
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