Effect of pipe roughness

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... 

Extensive studies (6) have been conducted to understand the effect of pipe roughness on friction loss in turbulent flow of Newtonian fluids in rough pipes. The phenomenon of turbulent flow with non-Newtonian fluids in rough pipes, however, has received very little attention (7). 

Increase is 0.029 or 2.9%. The actual effect of pipe roughness is much less than indicated by the ratio of the friction factors, and hs would in fact be less than he, not slightly greater. 

Bean, H.S. (1947). Indications of an orifice meter. American Gas Association Monthly 29 337. Bean, H.S. (1960). Effect of pipe roughness on orifice meter accuracy. American Gas Association New York. 

Figure 5.21. The friction factor (Eq. 5.132) as a function of Re, with effect of pipe roughness, k. (Adapted from Bird, R. B., Stewart, W. E., and Lightfoot, E. N. 1960. Transport Phenomena, Fig. 6.2-2.)...

In a comprehensive study carried out at roughly the same time by Durand(J5 36 3,) the effect of pipe diameter was examined using pipes of large diameter (40-560 mm) and a range of particle sizes dp. The experimental data were correlated by ... 

Medwell and Nicol [98, 99] were among the first to study the effects of surface roughness on condensate films. They condensed steam on the outside of one smooth and three artificially roughened pipes with pyramid-shaped roughness. All were oriented vertically, and the con-... 

In laminar flow/ = 16/Re, whereas in turbulent flow the dependence of/ on Re is a function of the specific rheological behavior of the fluid and roughness of the walls of the inside of the drill pipe (91). A number of functional relationships between / and Re have been proposed for turbulent flow. Ignoring the effects of the roughness of the surface of the drill pipe, / can be approximately related to Re by a generalized form of the well-known Blasius equation for Newtonian fluids (90, 95)... 

Comparing this with the definition of the friction factor, we see that the constant here is 4/. So far we have not included the effect of variable pipe roughness. It is plausible to assume that the constant in this equation is a function of pipe roughness, so that our final form is... 

Moody plot, chart, diagram A dimensionless representation of friction factor with Reynolds number tor a fluid flowing in a pipe. Presented on log-log scales, the diagram includes laminar, transition, and turbulent flow regimes. It also includes the effects of pipe relative roughness as a dimensionless ratio of absolute roughness with internal pipe diameter. The plot was developed in 1942 by American engineer and professor of hydraulics at Princeton, Louis Ferry Moody (1880-1953). 

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... 

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. 

A study was made of the effects of processing conditions and of blowing and nucleating agents and external lubricants on the apparent density, mechanical properties, linear thermal expansion coefficient and surface roughness of extruded cellular MDPE. Based on the results, recommendations were formulated for the properties of cellular MDPE pipes for the protection of light conducting cables. 16 refs. (Translation of Polimery, Tworzywa Wielkoczasteczkowe, No. 10, 1996, p.580). 

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