Turbulent Drag Reduction by Polyacryl Amide and Xanthan Gum, Experimental and Theoretical Investigation

          This work presents an experimental study of the drag-reduction performance of two water-soluble polymers, Polyacrylamide(PAAM) as flexible, linear synthetic polymer and Xanthan Gum(XG) as a rigid
polysaccharide from natural resources. The flow loop used consisted of 0.5 O.D. inch straight pipe with a test section of 3 m length. A 0.5 inch O.D. vertical tubing with elbows was also included to compare the drag- reduction behavior between both tubing configurations. Various concentrations of polymeric additive and water flow rates were tested.The results show that the drag-reduction in vertical piping are significantly lower than in straight type for both polymer type. The dragreduction efficiency of Xanthan Gum agent is much lower than polyacrylamide.Higher concentrations of XG about 150 ppm is required to
get  exactable drag-reduction performance about 12.84% in the straight pipe.While about 40.3% drag-reduction was achieved with about 50 ppm   Polyacrylamide with the same conditions. Moreover, the drag-reduction efficiency of XG can be improved by mixing with Polyacrylamide agent at a given conditions. Part of the experimental work was devoted to study the performance of Polyacrylamide as drag-reducing agent with the existence of small amounts of sodium chloride acts as an inhibitor to the ability of the additive, resulting in lower drag-reduction probably due to collapse of PAAM at more compact structure with the addition of sodium chloride as strong ionic salt.