Liquid phase mixing time was measured in 0.2 and 0.4 m i.d. columns over a wide range of superficial gas velocity (0.07-0.295 m s(-1)) and height-to-diameter ratio (1-10). A CFD model was developed for the prediction of flow pattern in terms of mean velocity and eddy diffusivity profiles. The predictions agree favourably with all the experimental data published in the literature. Complete energy balance was established in all cases. The validated CFD model was extended for the simulation of the macro-mixing process by incorporating the effects of both the bulk motion and the eddy diffusion. Excellent agreement was observed between the CFD predicted and experimental values of the mixing time over the entire range of D, V-G, and H-D/D covered. The model was further extended for the prediction of residence time distribution and hence the axial dispersion coefficient (D-L). The predicted values of D-L were found to agree very well with all the experimental data published in the literature.