In an earlier publication on partitioned bubble columns [Catal. Today 69 (2001) 165-170], liquid phase residence time distribution was measured in columns of 0.10, 0.15 and 0.38m diameter at superficial gas velocities, U-G, in the range 0.05-0.4 m/s. In the present study, CFD simulations, using two-dimensional Cartesian geometry and the Eulerian framework, are used to provide a theoretical back-round to our earlier experimental work. Both CFD simulations and experiments show that the (superficial) liquid exchange velocity, U-ex, at the partition plate is independent of column diameter; the exchange velocity U-ex is however found to be a strong function of the open area of the partition plates. The height of the gas cap forming underneath partition plates decreases significantly with increasing column diameter; this is a desirable result from the point of view of scale up. It is concluded that CFD simulations can be a powerful scale up tool. (C) 2003 Elsevier Science B.V. All rights reserved.