## finding fluid flow rate in a pipe, given pressure difference, length, and diameter

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

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Gold Member
 Quote by 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 h_L = head 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