# Homework Help: Finding fluid flow rate in a pipe, given pressure difference, length, and diameter

1. Nov 8, 2009

### Vidatu

1. The problem statement, all variables and given/known data

Oil flowing through a pipe, measured to be 135kPa 15m from the end and 88kPa discharging from the end. The diameter of the pipe is 1.5cm, the density of the oil is 876kg/m^3, and the dynamic viscosity is 0.24kg/m*s.
Find flow rate for:
a) horizontal
b) inclined 8 degrees
c) declined 8 degrees

2. Relevant equations

$$Re=V*D*\rho / \mu$$
$$\Delta P = h_L * \rho *g$$
$$h_L = f*(L/D)*(V^2)/(2*g)$$
$$f=64/Re$$ (laminar flow only)

where:
Re = Reynolds Number
rho = density$$f=64/Re$$
mu = dynamic viscosity
delta P = pressure loss
L = length
D = diameter
f = Darcy friction coefficient

3. The attempt at a solution
I solved for Re in terms of V, and for V in terms of f, and then I guessed f=0.0150 for a starting point. I got an Re of 13.8, indicating laminar flow, so I used $$f=64/Re$$ and iterated. However, my answer finally converged on f=12734.79 which doesn't look at all right. Am I doing something wrong?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 9, 2009

### defunc

Re: finding fluid flow rate in a pipe, given pressure difference, length, and diamete

Probably unit related. The equation for delta_p(your second equation) will have units in pascal.

3. Nov 10, 2009

### stewartcs

Re: finding fluid flow rate in a pipe, given pressure difference, length, and diamete

You need to show your work so we can give you guidance.

CS