Onset of gas induction and power consumption in an agitated tank having shortened narrower baffles

Abstract

The onset speed of gas induction and the power consumption after gas induction were studied in a gas-induced type agitated tank. In such an agitated tank, four unique baffles which were shorter and narrower than the conventional ones were adopted. Two 45° downward pitched blade turbines (PBT) in series were used as impellers. Gas induction could be formed by the dual impellers operated above the onset impeller speed. Several geometric factors and operation parameters were considered by theoretical aspects and the dimensionless analysis to study the onset of gas induction and the power consumption. In all experiments, air and tap water were used as working fluids. Results revealed that a lower agitation speed and less power consumption were needed for the present tank than a narrower full-length baffled agitated tank. In the present tank, the least specific power consumption was found when the liquid level was about 1.9 times the tank diameter. Two correlation equations were obtained to predict, respectively, the onset speed of gas induction and the power consumption after gas induction. Comparison between the present type and various other gas-inducing type agitated tanks were also discussed.