배관 Roughness Data

 

배관 거칠기 비율에 대한 Table 입니다.  

 

The friction coefficient - λ

The Friction Coefficient for Laminarflow

λ=64/Re(7)

The Friction Coefficient for Turbulentflow

λ = f( Re, k / dh ) 

k = relative roughness of tube or duct wall (mm, ft)

k / dh = the roughness ratio

Relative roughness for materials are determined by experiments. 

Relative roughness for some common materials can be found in the table below : 

 

Surface	Roughness - k
	x 10-3 m	feet
Copper, Lead, Brass, Aluminum (new)	0.001 - 0.002	3.33 - 6.7 10-6
PVC and Plastic Pipes	0.0015 - 0.007	0.5 - 2.33 10-5
Epoxy, Vinyl Ester and Isophthalic pipe	0.005	1.7 10-5
Stainless steel	0.015	5 10-5
Steel commercial pipe	0.045 - 0.09	1.5 - 3 10-4
Stretched steel	0.015	5 10-5
Weld steel	0.045	1.5 10-4
Galvanized steel	0.15	5 10-4
Rusted steel (corrosion)	0.15 - 4	5 - 133 10-4
New cast iron	0.25 - 0.8	8 - 27 10-4
Worn cast iron	0.8 - 1.5	2.7 - 5 10-3
Rusty cast iron	1.5 - 2.5	5 - 8.3 10-3
Sheet or asphalted cast iron	0.01 - 0.015	3.33 - 5 10-5
Smoothed cement	0.3	1 10-3
Ordinary concrete	0.3 - 1	1 - 3.33 10-3
Coarse concrete	0.3 - 5	1 - 16.7 10-3
Well planed wood	0.18 - 0.9	6 - 30 10-4
Ordinary wood	5	16.7 10-3

The Friction coefficient - Relative roughness for some common materials can be found in the table below :

1 / λ1/2 = -2,0 log10 [ (2,51 / (Re λ1/2)) + (k / dh) / 3,72 ] 

Roughness Ratio - k / dh.