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Homework Help: Calculate the gas flow rate.

  1. Apr 18, 2012 #1
    1. The problem statement, all variables and given/known data

    The pressure at the start of a 180Km stainless steel natural gas pipeline is 4MPa and at the end is 2MPa. If the diameter of the pipe is 0.4m, what will be the gas flow rate through the system? (ignore losses other than friction)

    (For natural gas, ρ = 40 kg/m^3, μ = 11x10^-6 Pas).

    2. Relevant equations

    u = q/a

    re = (u)(d)/v

    hf = p/(density)(g)(Q)

    3. The attempt at a solution.

    Kinematic velocity; \nu=11x10-6/40 = 2.75*10-7

    Reynolds number equation; Re = 1x10-6*0.4/2.75*10-7 = 16

    Re number < 2100 => flow is laminar

    From Moody's diagram, Friction Factor value = 0.002
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 20, 2012 #2
    A problem such as this involves a trial and error solution. Guess a velocity at the given upstream pressure of 4MPa . From this, determine the downstream pressure. If the pressure is too high, guess another upstream velocity and recompute the downstream pressure. Repeat the process until computed downstream pressure is 2MPa. Based on the final velocity, compute the mass flow.
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