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Calculate the total available energy from a water stream by use of a t

  1. Jun 13, 2013 #1
    I keep confusing myself on this question, basically i want to know how you would determine the amount of potential energy you could capture by using a turbine, if water is flowing down a pipe into a river.

    The change in elevation from the start to end of pipe is 30 meters.
    The pipe is 100 meters long.
    Water is flowing at a rate of 10 liters per second.

    Not assuming the efficiency of the water turbine itself, is the formula just the potential energy minus the friction in the pipe? Thus:
    Power per time = (Mass Flowrate X Gravitational constant X Change in Elevation) - Friction losses
    = ((10 L/s X 0.001 m3/L X 1000 kg/m3) X (9.81 m/s2) X (30 m)) - Friction
    = (2943 W/s or 2.94 kW/s) - Friction

    Also second question, I know how to calculate the friction in a pipe, but the problem i cannot get my head around is that because the pipe is nearly a meter in diameter, the pipe is not full of water, thus i dont know how to calculate Reynolds number etc? Any help here would also be appreciated,

    Thanks Guys
     
  2. jcsd
  3. Jun 14, 2013 #2

    256bits

    User Avatar
    Gold Member

    If only you knew the velocity of the stream....

    Why not try v = Q/A ; Q = volumetric flow rate, A = area of the stream, v= average velocity

    See as a reference,
    Open channel flow
    http://mysite.du.edu/~etuttle/tech/opench.htm
     
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