Mixing in Liquid-Jet-Agitated Tanks:  Effects of Jet Asymmetry

Mixing in liquid-jet-agitated tanks has been studied experimentally and numerically. A bottom-pump-around tank with a symmetric jet and another with an asymmetric jet arrangement were used. Conductivity was experimentally measured to determine the time required to achieve 95% mixing. Good agreement was obtained between the experimental and numerical results over a wide range of jet Reynolds numbers. Mixing time was found to be a function of the jet Reynolds number. A comparison of experimental and simulation results for bottom-pump-around and side-pump-around tank geometries, both having a symmetric jet, showed that, for jet Reynolds numbers, N Rej, less than 25 000, the side-pump-around tank geometry required less time to achieve 95% mixing. For N Rej greater than 25 000, the mixing times for the two arrangements were nearly the same. The up-angle is defined as the angle the jet makes with a horizontal plane parallel to the bottom of the tank. This angle has a significant influence on the 95% mixing time. The 95% mixing time for an up-angle of 20° is found to be about 50% of the 95% mixing time for an up-angle of 45°. The asymmetry of the jet was found to reduce the mixing time. The 95% mixing time when an asymmetric jet was used was found to be up to 34% less than that when a symmetric jet was used.