RHEOLOGICAL PROPERTY MEASUREMENTS OF DRAG-REDUCING POLYACRYLAMIDE SOLUTIONS

It has been suggested that an extra dimensionless group such as the Weissenberg or the Deborah number is necessary to correlate the drag and heat transfer reductions of very dilute polymer solutions in turbulent flows. It is demonstrated in this study that the characteristic time necessary for these dimensionless groups may be obtained from the Carreau model B. To achieve this, rheological properties of nine concentrations (0.012-2.0% by weight) of aqueous polyacrylamide solutions (Separan AP-273) were measured with the Weissenberg rheogoniometer (WRG). The measurements include the shear viscosity, the primary normal stress difference, the dynamic viscosity, and storage modulus. Parameters of the Carreau model B were then determined by simultaneously fitting all the experimental data. It is shown that the model adequately describes the experimental data and also that it is possible to establish the concentration dependence of these parameters. The model time constants A1and A2are found to decrease with decreasing concentration. The power law slope parameters are found to be relatively constant, while a decreases as expected, with decreasing concentration. It is demonstrated that with such concentration dependence, it is possible to predict material functions that cannot be measured experimentally by determining the model parameters through extrapolation. © 1978, The Society of Rheology. All rights reserved.