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Homework Help: Water pump with given conditions operating at inlet/outlet operating @ steady flo

  1. Oct 5, 2012 #1
    1. The problem statement, all variables and given/known data

    Average Velocity at Inlet = 2.50 m/s
    Pressure Abs. = 100 Kpa
    Elev = 2.00 m
    Inlet tube diameter 12.0 cm
    Water density 997 kg/m^3

    Average velocity at outlet = 8.00 m/s
    Elevation = 2.00m

    a.) Calculate mass flow rate through the pump
    b.) w/ an outlet pressure of 300 kPA what is required rate of shaft work input has 85% efficiency?

    2. Relevant equations


    3. The attempt at a solution

    My attempt was to just average the two Ave. velocities and plug into mass flow equation, not correct as I got no points on the HW. Part b.) I could not complete I would think it would involve calculating the change in mechanical, potential, and flow work and then multiplying kW by efficiency super frustrated. please help!
    Last edited: Oct 5, 2012
  2. jcsd
  3. Oct 5, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Not a good idea. Compute the mass flow based on input data. Mass flow out in unit time must be the same as mass flow in, must it not?
    Conservation of energy! What is the energy of 1 sec. worth of flow at the input & at the output.
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