Pipe roughness, equivalent

Pipe insulation, cost of, 513 Pipe painting, cost of, 514 Pipe roughness, equivalent, 480, 482 Piping standards, 492-494 Piping systems cost of, 173-174, 497-510 design of, 494-497 Plant ... 

Chapters 13 and 14 deal primarily with small deviations from plug flow. There are two models for this the dispersion model and the tanks-in-series model. Use the one that is comfortable for you. They are roughly equivalent. These models apply to turbulent flow in pipes, laminar flow in very long tubes, flow in packed beds, shaft kilns, long channels, screw conveyers, etc. 

Sexually mature male round gobies were collected by hook and line and bottom trawl between May and August in 1995 and 1996 from the St. Clair and Detroit Rivers (Windsor, Ontario). The fish were shipped by air to Edmonton (Alberta, Canada), where they were maintained under constant photoperiod (16L 8D) in 70L holding aquaria (3—5 fish per aquarium) provided with flowing dechlorinated tapwater at temperatures roughly equivalent to those in the field (9—18°C from winter to summer). Fish were fed a variety of live, frozen and flake food ad libitum. Aquaria contained gravel substrate, an airstone, artificial weed cover and plastic pipes for shelter. 

Example 2-3 Scale-Up of Pipe Flow. We would like to know the total pressure driving force (AP) required to pump oil (/z = 30 cP, p = 0.85 g/cm3) through a horizontal pipeline with a diameter (D) of 48 in. and a length (L) of 700 mi, at a flow rate (Q) of 1 million barrels per day. The pipe is to be of commercial steel, which has an equivalent roughness (e) of 0.0018 in. To get this information, we want to design a laboratory experiment in which the laboratory model (m) and the full-scale field pipeline (f) are operating under dynamically similar conditions so that measurements of AP in the model can be scaled up directly to find AP in the field. The necessary conditions for dynamic similarity for this system are... 

Thus, if we were to use the same pipe material (commercial steel) for the model as in the field, we would also have to use the same diameter (48 in.). This is obviously not practical, but a smaller diameter for the model would obviously require a much smoother material in the lab (because Dm -C Df requires em drawn tubing such as copper or stainless steel, all of which have equivalent roughness values of the order of 0.00006 in. (see Table 6-1). 

The length of straight pipe of given roughness which is equivalent in frictional resistance to the actual piping which contains bends and fittings. 

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... 

A large number of experimental data on friction factors of smooth pipe and pipes of varying degrees of equivalent roughness have been obtained and the data correlated. For design purposes to predict the friction factor/and, hence, the frictional pressure drop of round pipe, the friction factor chart in Fig. 2.10-3 can be used. It is a log-log plot of/... 

Hence, the flow is turbulent. For commercial steel pipe from the table in Fig. 2.10-3, the equivalent roughness is 4.6 x 10 m. 

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