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Volumetric flowrate of one substance to another

  1. Apr 1, 2010 #1
    Basically we have a valve that was tested with air and gave us a leak rate (MFR) of 0.046lbs/min of air. We need to know how much that equates to in Jet A Jet Fuel. The stats are: temperature ranging from 120 F to 200 F. Fuel temperature will range from -40F to 150F. Air pressure in the line will range from ~ 20-40 psig. Fuel pressure could be as high as 10 psig. Density of Jet A jet Fuel is about 6.7 lbs / Gallon US.

    Does anyone know how to figure out this conversion. Ask me any more info required and i'll see about getting it. Most of the people working on this are mechanical engineers and are not really good with this type of problem.
  2. jcsd
  3. Apr 1, 2010 #2


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    Science Advisor

    Actually Mechanical Engineers are really good at this type of thing.

    However, you can find the procedure for converting leak rates from gases to liquids on page 64 of this document:


    Hope this helps.

  4. Apr 1, 2010 #3
    Actually I meant electrical engineers, lol sorry about that.

    It was tested with air, and now we need to know how much will leak through the same valve with Jet Fuel. It's not a matter of converting from a gas vapor to the same substance in liquid form, it's a matter of going from one material and based on the test results with that one material getting a measurement for the other material, if that makes sense. Thanks for any help that has been or can be offered.
  5. Apr 1, 2010 #4
    You just need to use conservation of mass or conservation of momentum equation to solve this problem, remember navior stroke's equation to solve this. This question is very similar to my last week's homework question.
  6. Apr 1, 2010 #5


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    Science Advisor

    Doesn't matter...it can be the same fluid in different phases (i.e. gas or liquid) or it can be an entirely different fluid (i.e. air and jet fuel). You just need to know the dynamic viscosity of the fluids (which is indicative of the density of the fluid) and the pressure differential across the leak under test conditions.

    Take a closer look at the link I posted and the relative equations (perhaps read back a few pages). There is a procedure to estimate the liquid leakage rate based on a known gas leakage rate.

  7. Apr 1, 2010 #6


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    Staff: Mentor

    If you know the size (cross sectional area) of the leak and the pressure, bernoulli's equation will help you find the nozzle efficiency. Then apply Bernoulli's equation again to the other fluid, using the nozzle efficiency you just calculated.
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