The Drag Reduction of Dilute Polymer Solutions as a Function of Solvent Power,Viscosity,and Temperature.

摘要

The frictional drag reduction of high-molecular-weight polyethylene oxide and polystyrene solutions under turbulent flow conditions was studied as a function of temperature,solvent power,and solvent viscosity. A rotating disk apparatus was used to make the drag reduction measurements. For aqueous polyethylene oxide solutions,at concentrations well above that needed to produce maximum drag reduction,all drag reduction data reduced to a common curve when percent drag reduction was plotted against the Reynolds number for the flow. However,for polyethylene oxide solutions below this optimum concentration the drag reduction-versus-Reynolds number curves showed decreasing drag reduction with increasing temperature. The data are explained primarily in terms of the inverse temperature solubility characteristics of polyethylene oxide in water. The percent drag reduction of polystyrene in nonaqueous liquids was found to be greater in good solvents than in poor ones. It was also found that increases in solvent viscosity and decreases in temperature increased the percent drag reduction. The results are discussed in relation to the current drag reduction theories and are shown to be in opposition to Virk's theory. It is concluded from the data that drag reduction is very likely a function of a relaxation time phenomenon involving the polymer molecules and the flow system. The results also emphasize the importance of considering solvent power,viscosity,and temperature in the design of an efficient drag reduction system. (Author)