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Laminar at Re= 200,000?

  1. Jan 18, 2013 #1
    I am calculating Reynolds number for a automotive ac suction line with 16mm Id 300kpa and 10 deg C and 230 kg/hr. I am getting around 200,000. I think I got laminar flow, but the equation says turbulent. greater than 10,000. dynamic viscosity is my most questionable variable. i checked and double checked all my SI units. Anybody know if this Reynolds number is in the reasonable range?
  2. jcsd
  3. Jan 18, 2013 #2
    Sometimes when you are working with cars, although the flow might be theoretically laminar, we have to account for the vibrations that will most likely make it turbulent.

    You can still use the Reynolds number you obtained but with the turbulent equation.
  4. Jan 19, 2013 #3


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    What makes you think your flow is laminar?

    At any rate, for pipe flow, the diameter Reynolds numbers typically quoted for the onset of turbulent don't mean that the flow is instantly turbulent. It merely means the flow is unstable and will eventually become turbulent. If your tube is quite short, you could have extraordinarily high diameter Reynolds numbers and still be laminar for at least a short distance downstream.
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