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Pressure Change In Pipes

  1. Jan 12, 2016 #1
    How does change in pipe diameter affect pressure? For example, ethylene in a 6" pipe at 400 psi, enters a 1" pipe. How does the pressure change?

    I am fairly sure that pressure decreases and velocity increases. However, I need to know how pressure decreases? At what rate? Is it linear?
  2. jcsd
  3. Jan 12, 2016 #2
    I should point out, I do know how to calculate pressure loss across the length of a pipe. That is not what I am interested in.
  4. Jan 12, 2016 #3


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    Science Advisor

    Pipe friction is termed major losses, pressure drop due to fittings like valves, tees, or in your case a reducer (specifically a 6" to 1" reducer) are termed minor losses and are even easier to calculate. You can find an overview here:
    You'll have to do some more searching to find the minor loss coefficient for your specific fitting.
  5. Jan 12, 2016 #4


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    Staff: Mentor

    Pressure change, both due to velocity change and due to friction losses is a function of velocity. Since your starting pressure is high, if your velocity happens to be low, the pressure change may well be negligible.
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