Question

A 1-mile long 12-inch diameter asphalt dipped cast iron pipe (e = 0.00085 ft) conveys 60°F water at 3 cfs. Determine (a) friction factor f using the Moody Diagram, (b) f using the Colebrook equation, (c) head loss over the 1 mile distance, (d) slope of the EGL.

Problem 2 A 1-mile long 12-inch diameter asphalt dipped cast iron pipe (e = 0.00085 ft) conveys 60℉ water at 3 cfs Determine (a) friction factor fusing the Moody Diagram, (b) fusing the Colebrook equation, (c) head loss over the 1 mile distance, (d) slope of the EGL

Answer 1

Answers:

L = 1 mile

diameter = 12 inch = 1 ft

e = 0.00085 ft

temperature = 60 F

at this temperature:

kinematic viscosity = 1.21 * 10^-5 ft2 / s

Q = 3 cfs

a) velocity = v = Q /A

A = area = ( $\pi$ /4)*d^2

= ( $\pi$ /4)*1^2

= 0.785 ft2

v = 3 / 0.785

= 3.82 ft/s

Reynold's Number = Re = v*D / $\nu$

= 3.82 * 1 / (1.21*10^-5)

= 3.16 * 10^5  

roughness = e = 0.00085 ft

e/D = 0.00085 / 1

= 0.00085

From Moody's diagram e/D vs Re

f = 0.02

b) Colebrook equation

1/ sqrt(f) = - 2 * log[ (e/(3.7*D)) + 2.51 / (Re*sqrt (f) ) ]

1/ sqrt(f) = - 2 * log[ (0.00085/(3.7*1)) + 2.51 / (3.16*10^5*sqrt (f) ) ]

f = 0.0199

= 0.02

so same as MOODY's

c) head loss = h = f*L*v^2 / (2*g*D)

= 0.02 * 1*5280 * 3.82^2 / (2*32.2 *1)

= 23.93 ft