DEGRADATION EFFECTS OF DILUTE POLYMER-SOLUTIONS ON TURBULENT DRAG REDUCTION IN PIPE FLOWS

An important practical problem in the application and study of drag re duction by polymer additives is the degradation of the polymer, for in stance due to intense shearing, especially in recirculatory how system s. Such degradation leads to a marked loss of the drag-reducing capabi lity of the polymer. Three different polymer types were tested on degr adation effects in a closed pipe how system. The polymers used were Po lyox WSR-301, Separan AP-273 and Superfloc A-110, dissolved in water i n concentrations of 20 wppm each. The how system consisted of a 16.3 m m pipe of 4.25 m length. Two different pumps were used: a centrifugal pump and a disc pump. Different solution-preparation procedures were t ried and the experiments were performed at different flow rates. Super floc A-110 proved to be both the most effective drag reducer and most resistant to degradation. Because of very fast degradation, Polyox WSR -301 was found to be unsuitable for being used as a drag reducer in re -circulatory systems. The disc pump proved to be much better suited fo r pumping the polymer solutions than the centrifugal pump. The degrada tion curve of the combination Superfloc/disc pump showed a plateau-lik e region with reasonable drag reduction, which makes it possible to pe rform (laser Doppler) measurements under nearly constant circumstances during a sufficient time.