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Bemoulli equation ( flow in pipe)

  1. Feb 19, 2010 #1
    the bemoulli equation states that the energy per unit weight for a frictionless slow is constant.
    water at:
    30degree c = 0.801kgm-1s-1
    80degree c = 0.357kgm-1s-1
    Radiator 15kw
    delta T= 5degree c
    cp = 4.2kj/kgk
    pipe diameter 40mm

    is the flow in the pipe laminar or turbulent at 30 and 80 degree respectively

    what are the friction factors?

    i have the followin equation.

    reynolds number = velocity of fluid x density x diameter of pipe divided by viscosity of fluid.

    so i have 5x4.2x0.40 divided by0.801 = 10.48for 30
    and 5x4.2x0.4 divided by 0.357= 23.53for 80

    have i gone completely wrong as i was taught anything over 2000 is turbulant flow and anything under 2000 was laminar
     
  2. jcsd
  3. Feb 21, 2010 #2
    I learned 2300 whas the dividing line but 2000 might just be another good guide value.
    From what I see in your calculation of the Reynolds number you seem to have multiplied 5 C * 4.2 kJ/kg*K to calculate the fluid flow in meters/sec ? Check the units
     
  4. Feb 21, 2010 #3
    15 x 0.801 x 0.4 divided by 4.2 = 1.144?

    just using my formula the first part is the velocity of the fluid. i havnt been given this. do i rearange the formula or??
     
  5. Feb 22, 2010 #4
    5x4.2x0.40 divided by0.801 = 10.48for 30

    You have inserted 4.2 of what excatly for the density? Please refer to Wiki for a proper definition of the dimensionless Re-number.

    In units: (m/sec * kg/m^3 * m) / (kg/m*sec) = kg*m/sec / (kg/m*sec) = [-] unitless
    Check your answer using this type of units control.
     
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