The effect of drag reducing agent (DRA) on multiphase flow in upward and downward inclined pipes has been studied. The effect of DRA on pressure drop and slug characteristics such as slug translational velocity; the height of the liquid film slug frequency and Froude number has been determined. Experiments were performed in a 10-cm I. D., 18-m long Plexiglass pipes at inclinations of 2 and 15 degree for 50% oil-50% water-gas. The DRA effect was examined for concentrations ranging from 0 to 50 ppm. Studies were done for superficial liquid velocities between 0.5 and 3 m/s and superficial gas velocities between 2 and 10 m/s. The results indicate that the DRA was effective in reducing the pressure drop for both upflow and downflow in inclined pipes. Pressure gradient reduction of up to 92% for stratified flow with a concentration of 50 ppm DRA was achieved in 2 degree downward inclined flow. The effectiveness of DRA for slug flow was 67% at a superficial liquid velocity of 0.5 m/s and superficial gas velocity of 2 m/s in 15 degree upward inclined pipes. Slug translational velocity does not change with DRA concentrations. The slug frequency decreases from 68 to 54 slugs/minute at superficial liquid velocity of 1 m/s and superficial gas velocity of -l m/s in 15 degree upward inclined pipes as the concentration of 30 ppm was added. The height of the liquid film decreased with the addition of DRA which leads to an increase in Froude number.
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