The effect of drag reducing polymers on turbulent mass transfer

Mass transfer and drag reduction in turbulent flow of dilute solutions of Separan AP-30, a high molecular weight polyacrylamide, are examined. An electrochemical technique is employed to measure experimentally the time averaged value and fluctuations in the rate of mass transfer to the wall of a one inch diameter pipe. The electrochemical reaction used in this study is the diffusion limited cathodic reduction of tri-iodide ions in a potassium iodide electrolyte. The average mass transfer rate in polymer solutions is observed to be greatly reduced in comparison to that in the electrolyte solvent. This reduction is caused by two factors. First of all, it is observed that turbulent eddy mass transport is diminished in the wall region in polymer solutions. The physical properties of the polymer solution also differ from those of the solvent, causing the Schmidt number to increase from 700 to as high as 1250.