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

  • Thread starter Vidatu
  • Start date
  • #1
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Homework Statement



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

Homework Equations



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

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

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 [tex] f=64/Re [/tex] and iterated. However, my answer finally converged on f=12734.79 which doesn't look at all right. Am I doing something wrong?

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
55
0


Probably unit related. The equation for delta_p(your second equation) will have units in pascal.
 
  • #3
stewartcs
Science Advisor
2,177
3


Homework Statement



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

Homework Equations



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

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

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 [tex] f=64/Re [/tex] and iterated. However, my answer finally converged on f=12734.79 which doesn't look at all right. Am I doing something wrong?

Homework Statement





Homework Equations





The Attempt at a Solution


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

CS
 

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