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Homework Help: Thermodynamics water pump help

  1. Mar 17, 2008 #1
    1. The problem statement, all variables and given/known data
    HI guys, this is an exam review question from the Fundamentals Engr exam. Not sure how to do it, please help me along so I can learn it too!

    Water enters a pump steadily at T1=20°C, p1=100 kPa at a rate of 35 L/s and leaves at p2=800 kPa. The flow velocities at the inlet and the exit are the same, but the pump exit where the discharge pressure is measured at 6.1 m above the inlet section. Neglect Kinetic energy effect. The minimum power input to the pump is:

    (a) 34 kW (b) 22 kW (c) 27 kW (d) 52 kW (e) 44 kW

    2. Relevant equations

    0 = -W + m[tex]\dot{}[/tex]((h1-h2) + g(z1-z2))

    3. The attempt at a solution

    Well, I simplified the equation by eliminating Q(heat transfer) and KE. I converted kPA to Mpa by multiplying by .100.

    So, p1= .1 MPa, p2= .8MPa. The mass flow rate(m)= converted 35L/s to 0.035m^3/s by multiplying by .001. g is gravity which is 9.81m/s^2. z1= 0m and z2= 6.1m

    Basically, not sure how to start this problem out. Not sure how I find my h1 and h2. Maybe I'm not even using the correct equation, but I think I am.

    Thank you,
    Brad
     
  2. jcsd
  3. Mar 17, 2008 #2
    Okay, I found something else out...but have yet to figure out how to use the tables correctly. I think the water is classified as a compressed liquid, but that's as far as I've gotten.
     
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