# Homework Help: Bemoulli equation ( flow in pipe)

1. Feb 19, 2010

### donniemateno

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
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. Feb 21, 2010

### poso

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

3. Feb 21, 2010

### donniemateno

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??

4. Feb 22, 2010

### poso

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