Pipeline predicting pressure drop

Using the above exponents and pressure drop equations, the total pipeline air pressure drop and selected pressures were predicted for each Pipeline I, II and III, starting from the end of pipeline or points along the pipeline. Some of the predictions are presented in Fig. 17, from which it can be seen that the agreement between predicted and experimental values is quite good. 

Figure 8.1 shows the pressure and temperature of fluids in a flowline at various points along the ocean floor, predicted by a multiphase flow prediction program. As a unit mass of fluid traverses the pipeline, the pressure drops normally due to friction losses associated with fluid flow. However, the temperature decrease is more interesting. 

Two-phase flow often presents design and operational problems not associated with liquid or gas flow. For example, several different flow patterns may exist along the pipeline. Frictional pressure losses are more difficult to estimate, and in the case of a cross-country pipeline, a terrain profile is necessary to predict pressure drops due to elevation changes. The downstream end of a pipeline often requires a separator to separate the liquid and vapor phases, and a slug catcher may be required to remove liquid slugs. 

The smallest size pipeline loop usually considered for measurements intended for industrial scale-up is lin. (2.54 cm) inside diameter [178]. The results are used to determine laminar versus turbulent flow regimes and as input in flow models [178]. Nasr-El-Din [182,183] reviews the methods used to predict pressure drops across emulsions flowing in pipelines, as well as those used to sample and measure oil and solid concentrations in pipelines. An example of an equation for the prediction of water-in-crude oil (North Sea crude oil) emulsion viscosity is given in Equation (6.48). 

Bradley An Improved Method of Predicting Pressure Drop along Pneumatic Conveying Pipelines , Third Int Conf on Bulk Materials Storage, Handling and Transportation, Newcastle, NSW, 1989... 

Because concentrated flocculated suspensions generally have high apparent viscosities at the shear rates existing in pipelines, they are frequently transported under laminar flow conditions. Pressure drops are then readily calculated from their rheology, as described in Chapter 3. When the flow is turbulent, the pressure drop is difficult to predict accurately and will generally be somewhat less than that calculated assuming Newtonian behaviour. As the Reynolds number becomes greater, the effects of non-Newtonian behaviour become... 

When an industrial pipeline is to be designed, there will be no a priori way of knowing what the in-line concentration of solids or the slip velocity will be. In general, the rate at which solids are to be transported will be specified and it will be necessary to predict the pressure gradient as a function of the properties of the solid particles, the pipe dimensions and the flow velocity. The main considerations will be to select a pipeline diameter, such that the liquid velocity and concentrations of solids in the discharged mixture will give acceptable pressure drops and power requirements and will not lead to conditions where the pipeline is likely to block. 

The analysis of two-phase tubular contactors and pipelines is complicated because of the variety of configurations that the two-phase mixture may assume in these systems. The design engineer must have knowledge of the flow pattern that results from a given set of operating conditions if the in situ quantities such as pressure drop, holdup of each phase, phase Reynolds numbers, and interfacial area are to be determined. These in situ quantities must be known if the rate of heat transfer is to be predicted. 

New test-design procedures for the accurate prediction of pipeline pressure drop, including the effects due to horizontal/ vertical flow and bends. 

When evaluating a material for the purpose of establishing dense-phase and long-distance suitability, it is important to undertake all the necessary tests (e.g., particle sizing, particle and bulk densities, fluidization and deaeration). Also, if possible, it is useful to compare such results with those obtained on previously conveyed similar materials (e.g., fly ash). However, it should be noted that such an evaluation only is a qualitative one and it is not possible to predict say, minimum air flows or pipeline pressure drop based on such data (i.e., pilot-scale tests normally are required to confirm minimum velocities, friction factors, etc., especially over long distances and for large-diameter pipes). 

Good flow splitting design is dependent on the accurate prediction of the pressure drop caused by the various bends, branches and straight sections of pipe. This can be achieved by employing the above branch model(s), proven for the particular material and application, coupled with the accurate pipeline test-design procedure described in Sec. 2.4 of this chapter. 

The most reliable methods for fully developed gas/liquid flows use mechanistic models to predict flow pattern, and use different pressure drop and void fraction estimation procedures for each flow pattern. Such methods are too lengthy to include here, and are well suited to incorporation into computer programs commercial codes for gas/liquid pipeline flows are available. Some key references for mechanistic methods for flow pattern transitions and flow regime-specific pressure drop and void fraction methods include Taitel and Dukler (AIChEJ., 22,47-55 [1976]), Barnea, et al. (Int. J. Multiphase Flow, 6, 217-225 [1980]), Barnea (Int. J. Multiphase Flow, 12, 733-744 [1986]), Taitel, Barnea, and Dukler (AIChE J., 26, 345-354 [1980]), Wallis (One-dimensional Two-phase Flow, McGraw-Hill, New York, 1969), and Dukler and Hubbard (Ind. Eng. Chem. Fun-dam., 14, 337-347 [1975]). For preliminary or approximate calculations, flow pattern maps and flow regime-independent empirical correlations, are simpler and faster to use. Such methods for horizontal and vertical flows are provided in the following. 

The pressure drop and pumping requirements are functions of the type of flow and of the rheological properties of the dispersion. If the flow rate in a pipeline falls below the critical deposit velocity then particles or emulsion droplets will either sediment or cream to form a layer on the bottom or top wall, respectively, of the pipe. Some correlations that have been developed for the prediction of critical deposit velocity are discussed by Nasr-El-Din [86] and Shook et al. [90]. 

Examples of the use of models for the design of large-scale systems include the measurement of pressure drop and heat transfer in model heat exchangers, the mixing and rate of reaction in a bench-top batch reactor and the prediction of pressure drops in pipelines. 

Predicting the Pressure Drop for Flow of Emulsions in Pipelines... 

Predicting the pressure drop for pipeline transportation of such a fluid has not been an easy task. The rheological behavior of Orimulsion , as measured in concentric cylinder rheometers of flie Couette type, is shear thinning and only slightly viscoplastic and viscoelastic (63). At first, it was thought that these rheological data was reliable enough to predict the pressure drop in the pipeline. However, the field data have repeatedly showed that the actual pipeline pressure drop is systematically lower than the one predicted from the rheometric data (10). 

Finally, team checks the gas gathering and gas sales pipeline composition, temperature and pressure to initiate hydrate prevention measures. In parallel, the team checks the pressure drop versus flow rate in inlet gas gathering pipeline to detect/predict potential hydrate problem. This is important to prevent wet-gas or off-spec gas accidental releases in related processes. 

Outline the steps in the procedure for predicting pipeline pressure drop for slurries exhibiting power-law rheology. 

Define the Hedstrom number. How is this number used in prediction of pipeline pressure drop for slurries exhibiting Bingham plastic rheology ... 

Using the above models and method of feeding, the following optimal operating conditions were predicted for the extreme case of maximum pipeline length and maximum throughput. Note, a stepped-diameter pipeline was selected to minimize pressure drop, air mass flow rate and hence, conveying air velocities. 

The accurate prediction of thermodynamic properties of natural gas systems is of interest for gas industry. Compressibility factors are used in energy and flow metering. It is also used in calculations of gas pressure gradient in tubing and pipelines. When large volumes of gas are traded between produeers, distributors, and consumers, error in the estimation of the amount of involved are of real economic significance. In gas condensate reservoirs, well-productivity often declines rapidly when pressure drops below the dew point pressure near-wellbore. Therefore, it is very important to accurately determine the dew point pressure. The pressure and temperature of most natural gas mixtures can be found up to 150 MPa and 500 K, respectively (Nasrifar and Boland, 2006). At these eonditions, methane, ethane, and nitrogen are almost always supercritical while other hydroearbons are subcritical. Thus, the equation of state of natural gas mixture must be aeeurate at supercritical and subcritical behavior of methane and heavy hydrocarbons, respectively. 

Non-Newtonian flows are complex. A lab test in a pumping loop can yield very useful rheology data about the pressure drop. Scaling up to larger pipes is one method of predicting pipeline flows. Heywood et al. (1992) proposed the following methods ... 

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