Dispersed Pipe Flow Research Articles

Experimental Characterization and Evaluation of Crude Spiking Influence on Oil/Water Dispersed Flow in Pipe.

This study centers around examining the impact of introducing varying (small) quantities of crude oil into mineral oil (Exxsol D60) on the resultant properties of dispersions and emulsions in oil-salty-water mixture properties such as rheology, droplet size distribution, separation duration, and interfacial tension. The experimentation encompassed bottle tests and a compact flow loop configuration featuring a 2 m horizontal pipe segment. The findings indicate that blends of oil infused with crude oil, combined with salty water at water ratios of 25% and 50%, necessitate an extended duration for separation and for the establishment and stabilization of interfaces, in contrast to mixtures of unaltered oil and saline water. To illustrate, in samples with spiking concentrations ranging from 200 to 800 ppm within a 25% water fraction, the separation period escalates from 51 s to 2 min and 21 s. Interestingly, when the water fraction increased to 75 percent, the impact of crude oil spiking on separation time was minimal. The analysis revealed that the Pal and Rhodes emulsion viscosity model yielded the most accurate predictions for the viscosity of resulting emulsions. The introduction of crude oil spiking elevated emulsion viscosity while diminishing interfacial tension from 30.8 to 27.6 mN/m (800 ppm spiking). Lastly, a comparative assessment was performed between droplet size distributions in the devised dispersed pipe flow and observed in an actual emulsion system comprising crude and salty water.

Comments on “Drag reduction phenomenon in viscous oil–water dispersed pipe flow…” regarding slip ratio

In Rodriguez et al.1 an analytical expression was deduced to predict the slip ratio in dispersed oil-water flow. Although the quantitative agreement was quite good, the expression systematically underestimated the slip ratio. New experimental data of similar flows were collected in two different experimental facilities in pipes of different materials and diameters (26 mm and 82.8 mm i.d.). Oil-water flow data collected within a range of mixture Reynolds numbers from 1∙10^5 to 20∙10^6 in glass, acrylic and steel pipes with oil viscosities varying from 7 to 220 mPa.s were used to deduce a more generic correlation for slip ratio as a function of the mixture Froud number (5 < Fr < 70). The underestimation of the slip ratio was corrected. The new slip-ratio correlation can be used to significantly improve the prediction of volumetric fraction in flow situations where turbulent dispersion of oil in water occurs.

An experimental investigation and two-fluid model validation for dilute viscous oil in water dispersed pipe flow

In this work we investigated high viscous oil in water dispersions (Do/w) in pipe. The experiments are performed in a 22.8-mm-id 9-m-long horizontal glass pipe using a high viscous oil (density of 886kg/m3 and viscosity of 900mPas) and tap water as test fluids. Pressure gradients are collected; hold-up data are measured using the quick-closing-valves technique (QCV) and a capacitance sensor, specifically optimized for dispersed flows detection. A new two-fluid model for liquid–liquid dispersed pipe flow to predict hold-up, pressure gradient, and the slip ratio between the liquid phases is presented. The experimental data are compared at first with homogeneous model predictions. Then the presented two-fluid model is validated against experimental data of this work and against experimental data taken from the literature showing a good agreement. The predicted and measured slip ratio is grater than unity for all oil–water dispersions investigated.

Drag reduction phenomenon in viscous oil‐water dispersed pipe flow: Experimental investigation and phenomenological modeling

AbstractAn experimental study on drag‐reduction phenomenon in dispersed oil‐water flow has been performed in a 26‐mm‐i.d. Twelve meter long horizontal glass pipe. The flow was characterized using a novel wire‐mesh sensor based on capacitance measurements and high‐speed video recording. New two‐phase pressure gradient, volume fraction, and phase distribution data have been used in the analysis. Drag reduction and slip ratio were detected at oil volume fractions between 10 and 45% and high mixture Reynolds numbers, and with water as the dominant phase. Phase‐fraction distribution diagrams and cross‐sectional imaging of the flow suggested the presence of a higher amount of water near to the pipe wall. Based on that, a phenomenology for explaining drag reduction in dispersed flow in a flow situation where slip ratio is significant is proposed. A simple phenomenological model is developed and the agreement between model predictions and data, including data from the literature, is encouraging. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Effect of secondary flow on droplet distribution and deposition in horizontal annular pipe flow

In horizontal annular dispersed pipe flow the liquid film at the bottom is thicker and rougher than at the top of the pipe. A turbulent pipe flow experiencing a variation of roughness along the pipe wall will show a secondary flow. Such secondary flow, consisting of two counter-rotating cells in the cross-section of the tube, can change the distribution of the droplets inside the pipe and their deposition at the wall. Here, we compare the behaviour of the droplets (dispersed phase) with and without secondary flow, using large-eddy simulations. It is shown that the presence of secondary flow increases the droplet concentration in the core of the pipe and the droplet deposition-rate at the top of the pipe.

Statistical simulation of particle deposition on the wall from turbulent dispersed pipe flow

Deposition of particles towards the wall from a turbulent dispersed flow in a vertical pipe has been studied numerically. A fully developed turbulent pipe flow of air is chosen as the primary flow, and it is represented by the law-of-the-wall relations and the average turbulence statistics obtained from a direct numerical simulation reported in the literature. Trajectories and velocities of the particles are calculated, using a one-way coupling Lagrangian eddy–particle interaction model. Thousands of individual particles (typically 920 kg/m3 in density) of various diameters (2.0–68.5 μm) are released in the represented flow, and deposition velocities are evaluated. It is shown that the deposition velocities predicted are in good agreement with experimental data available in the literature. The influence of some forces in the particle equation of motion (i.e., the Saffman lift force, the centrifugal force, the conservation of angular momentum and the buoyancy force) on the prediction of the deposition velocities is examined. Also examined is the influence of the inlet particle concentration profile, on which little attention has been paid so far. The unique phenomenon of ‘near-wall build-up’ of small particles, which has been reported in some previous simulations and experiments, was also observed in the present simulation while the result for very small particles (τp+<3) should be accepted with reservation due to their possible spurious build-up associated with the random-walk approach.