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In this experimental work, the effect of the drag-reducing polymer on the holdup and slip ratio of the oil-water flow in three different horizontal acrylic pipes was investigated. The internal diameters (IDs) of the pipes were 30.6-mm, 55.7-mm and 74.7-mm. The flow conditions of the oil-water flow consisted of 0.4–1.6 m/s mixture velocities and 0.1–0.9 input oil volume fractions. The master solution of the polymer (commercially known as AN 105-SH) was prepared at 2000 ppm concentration and injected into the water phase at controlled flow rates to provide 40 ppm concentration in the phase. The measurement of the holdup was carried out with help of quick closing valves after which the slip ratio was determined. The results showed that the water holdup and by extension, the slip ratio before the addition of the DRP increased with increase in the input oil volume fraction at low mixture velocity while the reverse was the case at high mixture velocity. The addition of the DRP increased the water holdup and the slip ratio only in water-dominated flow regions in all the three pipes. Finally, the increase in the pipe diameter also increased the water holdup and the slip ratio before and after the addition of the DRP in most of the flow conditions.

In this work, the results of the experimental investigations of oil-water flow in the absence and presence of water-soluble drag-reducing polymer in two different horizontal pipe diameters (55.7 and 74.67-mm ID) and their comparisons with the results in horizontal 30.6-mm ID pipe were presented. During the study, mixture velocity of the oil-water flow was varied from 0.1 to 1.6 m/s while the input oil volume fraction was varied from 0.05 to 0.9. At each experimental run, the polymer master solution of 2000 ppm concentration was injected into the flow at a controlled flow rate such that 40 ppm concentration of the polymer was achieved in the water phase. The six flow patterns previously observed in the 30.6-mm ID pipe reduced to four in the larger pipes. Although the presence of the polymer only affected the water-continuous flow patterns just like in the 30.6-mm ID pipe, the increase in the pipe diameter increased the regions of separated flow patterns before and after the addition of the polymer. Similarly, the frictional pressure gradients were significantly decreased by the polymer addition in all the three pipes resulting to huge drag reductions, which virtually decreased with increase in the pipe diameters.

An experimental investigation of the effect of various mixtures of different polymers on drag reduction was studied in a dispersed horizontal oil-water flow. The study was carried out in a horizontal pipe flow loop system of 30.6-mm ID and 24 m length. All the polymers are anionic water-soluble polymers prepared in 1000 ppm master solution and injected at different flow rates to achieve polymer concentrations in the range of 5 to 30 ppm in the water phase. As expected, the percentage drag reductions of the individual polymers and of the binary polymer mixtures increased with the increase in the mixture velocity but decreased with the increase in the oil fraction. It has been found that the drag reduction of the mixed polymer solution is higher than the drag reduction of the lower molecular weight polymer. In most of the cases, the drag reduction of the binary mixtures shows a positive deviation from the additive straight lines. The positive deviation is more dominant for the mixture of the high and low molecular weight polymers than the mixture of the high and medium molecular weight polymers. Also, the drag reductions of the mixture of the high and low molecular weight polymers are higher than the drag reductions of the mixture of the high and medium molecular weight polymers. Finally, although positive deviation was observed in this study, no synergism was obtained for all the investigated polymer-polymer mixtures conditions.

This study deals with development and evaluation of empirical correlation for predicting pressure gradients of oil-water flow after the addition of drag-reducing polymer. The experimental pressure gradient data used for the correlation were obtained from three different acrylic pipe diameters (30.6, 55.7 and 74.7 mm) at different inclination angles. The drag-reducing polymer (DRP) which was a water-soluble copolymer of polyacrylamide and 2-acryamido-2-methylpropane sulfonic acid, was injected at 40 ppm concentration into the water phase of the oil-water flow. The flow conditions of 0.4–1.6 m/s mixture velocities and 0.05–0.9 input oil volume fractions were imposed. The measured pressure gradient data after the addition of the DRP were used to develop a friction factor correlation as a function of mixture Reynolds number. The developed correlation when tested against the current and previously published experimental data showed a good performance. It also showed the best performance when compared with similar existing correlation and homogeneous model.

In this study, the influence of a drag-reducing polymer on oil–water flow patterns and pressure gradients was investigated in a downward-inclined pipe (−5°) and compared with the results obtained in a horizontal pipe for the same flow characteristics. Drag reduction was achieved by adding 40 ppm of polymer into an oil–water flow in an acrylic pipe of 0.0306 m ID flowing at 0.1–1.6 m/s mixture velocities and 0.05–0.9 input oil volume fractions. The downward inclination enhanced the mixing of the two phases and hence the boundaries between the dispersed and separated flows occurred at lower mixture velocities in downward flow than in horizontal flow. In both pipe orientations, the addition of the DRP affects the flow patterns and pressure gradients mainly in the water-dominated flow regions. Compared with those of the horizontal flow, the effect of polymer addition on flow pattern boundaries was generally lower at −5° inclination. The effect of the polymer on the pressure gradients was more pronounced at horizontal flow than at −5° flow, resulting in a maximum drag reduction of 64% and 55% at horizontal and −5° flows, respectively. Since the polymer used is water-soluble, there were no observable changes in the flow characteristics at the oil-dominated flow regions.