1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook