Roughness commercial pipes

In laminar flow,/is independent of /D. In turbulent flow, the friction factor for rough pipe follows the smooth tube curve for a range of Reynolds numbers (hydrauhcaUy smooth flow). For greater Reynolds numbers,/deviates from the smooth pipe cui ve, eventually becoming independent of Re. This region, often called complete turbulence, is frequently encountered in commercial pipe flows. The Reynolds number above which / becomes essentially independent of Re is (Davies, Turbulence Phenomena, Academic, New York, 1972, p. 37) 20[3.2-2.46ln( /D) ... 

For commercial pipe with roughness e = 0.046 mm, the friction factor is about 0.0043. Approaching the last hole, the flow rate, velocity and Reynolds number are about one-tenth their inlet values. At Re = 16,400 the friction factor/is about 0.0070. Using an average value of/ = 0.0057 over the length of the pipe, 4/Z73D is 0.068 and may reasonably be neglected so that Eq. (6-151) may be used. With C, = 0.62,... 

The friction factor in Equations 2-54 and 2-55 is a function of the surface roughness of the pipe and the Reynold s number. Typical surface roughnesses of new commercial pipes are shown in Table 2-9. Old or corroded pipes may have a significantly higher roughness. 

Values of Absolute Roughness, New, Clean, Commercial Pipes [1]... 

Absolute roughness commercial steel pipe, Table 5.2 = 0.046 mm... 

Absolute roughness commercial steel pipe, table 5.2 = 0.46 mm Relative roughness, e/d = 0.046/40 = 0.001 Friction factor from Figure 5.7, / = 0.0027... 

Reynolds number and the pipe roughness. The roughness of typical commercial pipe is 0.045 mm (0.000 15 ft). 

Commercially available pipes differ from those used in the experiments in that the roughness of pipes in the market is not uniform and it is difficult to give a precise description of it. Equivalent roughness values for some commercial pipes are given in Table 8-3 as well as on the Moody chart. But it should be kept in mind that these values are for new pipes, and the relative roughness of pipes may increase with use as a result of corrosion, scale... 

Absolute roughness commercial steel pipe. Table 5.2 = 0.046 mm Relative roughness = 0.046/(25 x 10 3) = 0.0018, round to 0.002 From friction factor chart. Figure 5.11, f = 0.0032... 

Figure 4.1 Moody diagram Fanning friction factor, f, vs. Reynolds number for the range of commercial pipe relative roughnesses.

It should be noted that the horizontal portions of the curves to the right of the broken line are represented by Nikuradse s [60] correlation, which is presented in Table 5.9. The downward-sloping line for the smooth turbulent flow is represented by the PKN correlation shown in Table 5.8. The downward-sloping line for laminar flow is represented by Eq. 5.17. Relative roughness e can be obtained from Table 5.10 for a variety of commercial pipes. 

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