Pipes roughness

Figure 1 shows the particulate loading of a pipe containing gas and particulates where the nonuniformity induced by a disturbance, ie, a 90° bend, is obvious (2). A profile of concentration gradients in a long, straight, horizontal pipe containing suspended soHds is shown in Figure 2. Segregation occurs as a result of particle mass. Certain impurities, eg, metal-rich particulates, however, occur near the bottom of the pipe others, eg, oily flocculates, occur near the top (3). Moreover, the distribution may be affected by Hquid-velocity disturbances and pipe roughness.

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... 

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... 

A pump lifts water from a lake. At the pump suction entry a foot valve is fitted. Determine the maximum static delivery height the water can be raised without cavitation taking place. The saturation pressure of water is 1.23 kPa at 10 °C and the dynamic viscosity is 1.3 x 10" kg m s T The suction pipe water velocity is 2.0 m s , the internal pipe diameter is 100 mm, and the pipe roughness is 0.03 mm. The resistance of the foot valve is 4.5. 

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.

From Table 2-10, a 6-inch pipe has a velocity of 5.55 fps at 500 gpm and a head loss of 0.720 psi/100 ft. The 5-inch pipe has a velocity of 8.02 fps and might be considered however 5-inch pipe is not commonly stocked in many plants, and the velocity is above usual economical pumping velocities. Use the 6-inch pipe (rough estimate). 

Condensate, Ibs/hr (Equation 2-133) or for pipe, Williams and Hazen constant for pipe roughness, (see Cameron Table 2-22 and Figure 2-24) or flow coefficient for sharp edged orifices... 

Flexible pipes Roughness varies considerably with conshuction. Smooth rubber hose corresponds approximately with steel pipe. Head loss when curved can be 30% higher than when straight... 

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)... 

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. 

Note that we have an additional fluid property (m and n instead of /z), but we also assume that pipe roughness has a negligible effect, so the total number of variables is the same. The corresponding dimensionless variables are / ARe pl, and n [which are related by Eq. (6-47)], and the unknown (DF = ef) appears in only one group (/). The procedure just followed for a Newtonian fluid can thus also be applied to a power law fluid if the appropriate equations are used, as follows. 

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... 

Determine pipe roughness e from Table 4-1. Compute eld. 

Another modification of the Lockhart-Martinelli approach has been proposed by Chisholm and Laird (C4) to account for the effect of pipe roughness. For the turbulent-turbulent region, it is suggested that the Lockhart-Martinelli correlations, which were presented graphically, can be represented by the equation... 

If X > 0.4, the last term is negligible. On the basis that the exponents on the flow terms in the definition of X vary as a function of pipe roughness, it was found that plots of — 1) against C/X gave straight lines,... 

---