Transportation in pipes

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

The mechanism by which solids are distributed throughout a vessel once they are suspended is different from that leading to suspension. It might be expected that the solids distribution would again be affected by the bulk flow pattern, i.e. the mean velocities throughout the vessel as well as the turbulence structure. These flows oppose the gravitational downwards force. As will be shown later, the measured vertical concentration profiles are very complicated, much more so than in solids transport in pipe flow, for example, where a steady decrease in concentration occurs from top to bottom. This concentration decay in pipes can be modelled rather easily by a one dimensional sedimentation-dispersion model. A similar model has been proposed for stirred vessels for the region above the impeller. 

Pollert, J., Kolar, V., Havlik, V. Drag reduction in hydraulic transport in pipes. IV Seminar on Transport and Sedimentation of Solid Particles/ Wroclaw/ Paper A21/... 

Schiller, R. E., andP. E. Herbich. 1991. Sediment transport in pipes. In Handbook of Dredging, Edited by P. E. Herbich. New York McGraw-Hill. 

Isothermal Gas Flow in Pipes and Channels Isothermal compressible flow is often encountered in long transport lines, where there is sufficient heat transfer to maintain constant temperature. Velocities and Mach numbers are usually small, yet compressibihty effects are important when the total pressure drop is a large fraction of the absolute pressure. For an ideal gas with p = pM. JKT, integration of the differential form of the momentum or mechanical energy balance equations, assuming a constant fric tion factor/over a length L of a channel of constant cross section and hydraulic diameter D, yields,... 

For dense phase transport in vertical pipes of small diameter, see... 

The most important transition velocity, often regarded as the minimum transport or conveying velocity for settling slurries, is V 9- The Durand equation (Durand, Minnesota Int. Hydraulics Conf., Proc., 89, Int. Assoc, for Hydraulic Research [1953] Durand and Condohos, Proc. Colloq. On the Hyd. Tran.spoti of Solids in Pipes, Not. Cool Boord [UK], Paper IV, 39-35 [1952]) gives the minimum transport velocity as... 

Estimation of Transportation Velocity of Solid Particles in Pipe Flow at Various Inclination Angles 1335... 

An example where reactant concentration is solely governed by corrosion considerations is in the production of concentrated nitric acid by dehydration of weak nitric acid with concentrated sulphuric acid. The ratio of HN0j H2S04 acid feeds is determined by the need to keep the waste sulphuric acid at > 70 Vo at which concentrations it can be transported in cast-iron pipes and stored after cooling in carbon-steel tanks. 

There were several studies of hydraulic transport in the 1950s, sparked off particularly by an interest in the economic possibilities of transportation of coal and other minerals over long distances. Newitt et al.p2) working with solids of a range of particle sizes (up to 5 fim) and densities (1180-4600 kg/m3) in a 25 mm diameter pipe, suggested separate correlations for flow with a bed deposit and tor conditions where the particles were predominantly in heterogeneous suspension. 

Sand with a mean particle diameter of 0.2 mm is to be conveyed in water flowing at 0.5 kg/s in a 25 mm internal diameter horizontal pipe 100 m long. Assuming fully suspended flow, what is the maximum amount of sand which may be transported in this way if the head developed by the pump is limited to 300 kN/m2 ... 

Sand of particle size 1.25 mm and density 2600 kg/m3 is to be transported in air at the rate of I kg/s through it horizontal pipe 200 m long. Estimate the pipe diameter, the pressure drop in the pipeline and the air flow required. 

Z.ANDl. I. (cd) In Advances in Solid-Liquid Flow in Pipes and its Applications. Hydraulic Transport of Bulky Materials (Pergamon, Oxford, 1971). 

Durand, R. Ptoc. of the Minnesota Internationa] Hydraulic Convention (1953) 89. Basic relationships of transportation of solids in pipes — experimental research. 

Durand, R, and Condolios, E. Proceedings of a Colloquium on the Hydraulic Transport of Coal, National Coal Board, London (1952), Paper IV. The hydraulic transportation of coal and solid materials in pipes. 

The production of turbulence is maximum close to walls, where both shear rate and turbulent viscosity, ut, are high. In pipe flow, the maximum is close to y+ = 12. A proper design of a chemical reactor for efficient mixing at low Re should allow the generated turbulence to be transported with the mean flow from the region where it is produced to the bulk of the fluid where it should dissipate. 

Highly viscous petroleum oil containing 30% to 80% water can be transported through pipes more efficiently when a 1 1 mixture of washing liquid and antifreeze (i.e., ethylene glycol with borax) is added to the oil in amounts of 0.002% to 0.2% by weight. In addition to increased efficiency of transport, reduced corrosion of pipes can be achieved [893]. 

In a chemical plant, time delay is usually a result of transport lag in pipe flow. If the flow rate is fairly constant, the use of the Smith predictor is acceptable. If the flow rate varies for whatever reasons, this compensation method will not be effective. 

In this case, the flow rate is to be determined when a given fluid is transported in a given pipe with a known net driving force (e.g., pump head, pressure head, and/or hydrostatic head). The same total variables are involved, and hence the dimensionless variables are the same and are related in the same way as for the unknown driving force problems. The main difference is that now the unknown (Q) appears in two of the dimensionless variables (/ and 7VRe), which requires a different solution strategy. 

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