Pipes roughness factors

Figure 2-24. Friction loss for flow of water in steel pipes. Note C = pipe roughness factor. See Tables 2-9 and 2-22. Courtesy of Carrier Corp.

Sample problem B shown in Fig. 22 is taken from Gay and Middleton (Gl). All nodes in this network are at the same elevation and all pipes are 100 ft long and 6 in. in diameter. The values of fluid density and viscosity, and pipe roughness factor are taken to be the same as in the previous problem. Tables XI and XII summarize the numerical description of this network including initial guesses and final solution. 

The pipe roughness factor is found in Table 2.5. The constants for the fittings are found in Table 2.4. 

Example 6 Losses with Fittings and Valves It is desired to calculate the liquid level in the vessel shown in Fig. 6-15 required to produce a discharge velocity of 2 m/s. The fluid is water at 20°C with p = 1,000 kg/m and i = 0.001 Pa - s, and the butterfly valve is at 6 = 10°. The pipe is 2-in Schedule 40, with an inner diameter of 0.0525 m. The pipe roughness is 0.046 mm. Assuming the flow is tiirhiilent and taking the velocity profile factor (X = 1, the engineering Bernoulli equation Eq. (6-16), written between surfaces 1 and 2, where the... 

This K factor is approximately proportional to the roughness of pipe (friction factor) and inversely proportional to the pipe diameter ... 

The value of C3 is 0.011454 in USCS units and 20.178 x 10 in SI units. The inputs for the calculation are Q (bbl/hr or mVhr) and pipeline length (miles or km), viscosity U (Centistokes), pipe diameter D (inches or meters), effective pipe roughness e, and pipeline lengths (miles or km). The Fanning friction factor is... 

Figure 2-11. Relative roughness factors for new clean pipe. Reprinted by permission from Pipe Friction Manual, 1954, The Hydraulic Institute. Also see Engineering Data Book, 1st Ed., 1979, The Hydraulic Institute. Data from L. F. Moody, see note Figure 2-3.

Type of Pipe Degree of Roughness Velocity ft/min Roughness Factor (Use as multiplier)... 

While a high velocity of flow will produce turbulence in any pipe, other factors contribute to turbulence. Among these are the roughness of the inside of the pipe. 

A constant value of the friction factor f = 0.009 is assumed, for fully developed turbulent flow and a relative pipe roughness e = 0.01. The assumed constancy of f, however, depends upon the magnitude of the discharge Reynolds number which is checked during the program. The program also uses the data values given by Szekely and Themelis (1971), but converted to SI. 

The friction factor is a dependent on the Reynolds number and pipe roughness. The friction factor for use in equation 5.3 can be found from Figure 5.7. 

Extraction factor in liquid-liquid extraction (-), or pipe roughness (mm)... 

Rf = ratio of rough pipe friction factor to smooth pipe friction factor, 1.0-2.9... 

Although Eq. (9-17) appears to be explicit for G, it is actually implicit because the friction factor depends on the Reynolds number, which depends on G. However, the Reynolds number under choked flow conditions is often high enough that fully turbulent flow prevails, in which case the friction factor depends only on the relative pipe roughness ... 

The Fanning friction factor/is a function of the Reynolds number Re and the roughness of the pipe e. Table 4-1 provides values of e for various types of clean pipe. Figure 4-7 is a plot of the Fanning friction factor versus Reynolds number with the pipe roughness, eld, as a parameter. For laminar flow the Fanning friction factor is given by... 

Using the relative roughness factor and friction factor to be 0.0006 and 0.004 again. The frictional loss in the pipe is... 

Pipe roughness, or friction factor /, can be obtained with the pipe supplier or in piping books. As a reference, commercial steel piping roughness is assumed 0.00015 ft for schedule 40- and 80-type pipes. The following table provides some guidance but is not to be used as reference. 

Note that e, commonly referred to as the absolute roughness factor, is in feet of pipe, and ranges from 0.00015 for new smooth pipe to 0.001 for rough old pipe. This factor may also be 0.01 to 0.05 for severely corroded and scaled pipe. 

FIGURE 3B Roughness factors for selected types of pipe materials. [Adapted from Moody, L. F. (1944). Trans. ASME 66, 671-684.]... 

At higher Reynolds numbers, the friction factor is affected by the roughness of the surface, measured as the ratio e/D of projections on the surface to the diameter of the pipe. Glass and plastic pipe essentially have = 0. Table 7-11 gives the pipe roughness of various materials. Figure 7-22 shows plots of Darcy friction factor versus Reynolds number for various pipe sizes. Alternatively, an explicit equation for the friction factor is given by [30] ... 

The friction factor, f, depends on the Reynolds number and the relative roughness, e/D. Table 8.4 contains roughness factors, s, for several pipe materials. Surface roughness is very irregular and non-uniform. Thus, e for any pipe material is an average value. Figure 8.16 is a plot of the friction factor as a function of Reynolds number with the relative roughness as a parameter. 

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