Material
|
Roughness ε (m)
|
Plastic
|
3.0 x 10-7
|
Steel
|
4.6 x 10-5
|
Galvanized
iron
|
1.5 x 10-4
|
Concrete
|
1.2 x 10-4
|
Problem 3:
Determine friction factor if
water at 160 F is flowing at 30 ft/s in an uncoated ductile iron pipe having an
inside diameter of 1.0 inch.
Determine Reynolds number:
νη ρ DVDV NR =
D = 1/12 = 0.0833 ft; V = 30
ft/s; ν =
4.38 x 10-6 ft2/s
NR = 5.70 x 105
So its turbulent flow, we will
have to use Moody diagram
Determine relative roughness
– ε for ductile iron pipe from the table in text
= 8 x 10-4 ft
D/ ε = 0.0833/8 x 10-4 = 104
