The experimental study was primary designed to evaluate the effectiveness of various additive types as drag-reducer agents, both in the single and binary mixed forms. Since a comparison between more than one additives type, especially between water soluble polymers and suspended particles are rare in literature. The additives, which have been investigated in present work, were Polyethylene Oxide (PEO) and Polyacrylamide (PAAM) up to 100 ppm, as flexible, long chain, synthetic polymers and Xanthan Gum (XG (up to 200 ppm, as a rigid natural polysaccharide polymer. Furthermore, a certain type of natural Clay (Kaolin) was concluded as suspended particles additive up to 1000 ppm, in addition to Aluminum Sulfate (Alum) up to 500 ppm, and Trisodium polyphosphate (STPP) were investigated, up to 200 ppm, in the present investigation. Alum and STPP were used for first time as drag reducing agents. The drag-reduction efficiency of the flexible polymers, PEO and PAAM is larger than that of other used additives in a whole concentration range at different flowing velocities A maximum dragreduction of about 32% has been achieved when 100 ppm PEO and PAAM were added at 6.0 m3/hr flow rate, these it has been considered as an optimum one between the other types of additive.Xanthan Gum, Clay, and Trisodium polyphosphate showed a moderate efficiency as drag-reducer additives. While, Alum was more efficient at concentrations 500-1000 ppm, which gave 21-25% drag-reduction probably, due to form colloid with water, which causes lowering the solution viscosity. A slight increase of drag-reduction was observed by mixing of Clay, Alum or STPP with PEO and PAAM, while, a significant enhancement of drag-reduction ability for Xanthan Gum was obtained by mixing with Clay, Alum or STPP combined additives. Friction factor values were calculated from experimental data observed for all considered additives at different flowing conditions. Friction factor lines for Polyethylene Oxide, Polyacrylamide and Alum at high Reynolds number positioned towards Virk asymptote, which was never reached.
