Effects of the Molar Ratio of Counter-Ions on Flow Characteristics of Surfactant Solutions Sweeping Cavities

Abstract

An experimental study has been performed in order to investigate the optimum rheological characteristics for a technique of heat transfer augmentation in a cavity between ribs mounted in parallel plates. The rheological characteristics of visco-elastic fluid were changed by controling the molar ratio of counter-ion to a cationic surfactant. Flow visualization experiments and pressure loss measurements were conducted in the range of solvent Reynolds number from 100 to 2,500 and in the range of molar ratio from 0.50 to 10. Under this condition, the zoro-shear Reynolds number and the Weissenberg number ranged from 2.01 to 120 and from 1.94 × 10^-2 to 9.15, respectively. From the results, flow penetration into the cavity occurred in the cases from 1.5 to 5.0 of molar ratio of counter-ions. However, the pressure loss became large in the cases when the remarkable Barus effect can be observed. On the other hand, the pressure loss became almost the same as that of water in the case when the molar ratio of counter-ions was set at 5.0. From this, it was concluded that the optimum fluid for the heat transfer augmentation in a cavity is required to have suitable elasticity and low viscosity as the molar ratio of counter-ions is set around 5.0.