No abstract

The hydrodynamic and mass transfer characteristics in countercurrent, cocurrent and liquid batch operations with various Newtonian liquids were studied experimentally using the same bubble column. Taking the effects of gas sparger geometries, operating variables and liquid properties into account, empirical correlations were obtained for the gas hold-up and the volumetric liquidphase mass transfer coefficient.

Axisymmetric jets have been observed to investigate the effect of controlled pulsation on the behavior of vortex rings by using the hydrogen bubble technique and hot-film measurement. Pulsed jets had similar velocity profiles in the initial region and in the fully developed region. This similar velocity profile was coincident with that in natural jets. The differences between the two kinds of jets in volume rate, in decay of centerline velocity and in distribution of turbulent intensity, were observed to be remarkable in the initial region. Such differences were caused by the different behavior of vortex rings in the initial region. Behavior of vortex rings in the initial region of pulsed jets was roughly classified into three types by Strouhal number, Sr0 (Sr0 <0.9, 0.9^Sr0 < 2.6, Sr0^2.6). It was found that the pulsation for Sr0 =0.3 was the most dispersive wave in a jet column.

Counter current bubble columns have the feature that specific gas‐liquid interfacial area and gas holdup are larger than those for standard and cocurrent bubble columns. In this study, three different flow regimes, churn‐turbulent flow, bubble flow and bubble down‐flow, have been observed in a counter‐current bubble column and correlations of gas holdup and volumetric liquid‐phase mass transfer coefficient have been proposed as functions of operating variables such as the superficial velocities of gas and liquid, the gas‐liquid slip velocity and the liquid properties.

The operational variables of electrokinetic remediation have not been cleared yet, because this method is relatively new and is an innovative technique in the aquifer remediation. In order to investigate the operational variables of the electrokinetic remediation, a mathematical model has been constructed based on the physico chemical mass transport process of heavy metals in pore water of contaminated aquifer. The transport of the heavy metals is driven not only by the hydraulic flow due to the injection of the purge water but also by the electromigration due to the application of the electric potential gradient. The electric potential between anode and cathode is the important operational variable for the electrokinetic remediation. From the numerical simulations with use of this model it is confirmed that the remediation starts from the up stream anode and gradually the heavy metal is transported to the down stream cathode and drawn out through the purge water.