Effect of solvent chemistry on critical weissenberg numbers

Abstract

The critical Weissenberg number for the friction factor was earlier reported to be approx. 5–10 for turbulent pipe flow of 1000 wppm polyacrylamide dissolved in Chicago tap water, while the corresponding critical Weissenberg number for the dimensionless heat transfer coefficient, j H , was found to be approx. 200–250 for this same solution. It is known that the chemistry of the solvent generally influences the friction and heat transfer behavior of a polymer solution. Experiments have been performed using 100 wppm sodium hydroxide as an additive to the aqueous polyacrylamide solution (Separan 1000 wppm) and reveal that the critical Weissenberg numbers are unaffected. It is tentatively concluded that the chemistry of the solvent does not influence the critical Weissenberg numbers for aqueous polyacrylamide solutions. Preliminary measurements using aqueous solution of polyethylene oxide (Polyox 5000 wppm) yield critical Weissenberg numbers which are in reasonable agreement with the values reported earlier for aqueous solutions of polyacrylamide.