Results and discussion
The above promising results motivated the second step of thescale-up methodology; the actual comparison between datagenerated within the tubes bundle and that within a solid wallbubble column. This motivation stems from the finding thatthe proposed arrangement of internals could mimic the solidwall effect as shown above.Independent results of radial gas holdup profiles obtainedby Xue (2004) and Wu (2007) using the optical probe techniquein a separate unit consisting of solid wall column of the samediameter as our bundle of tubes are compared with the datagenerated in the current study.Figs. 8–10 illustrate the gas holdup radial profiles in the twosystems for Ug= 20 cm/s, 30 cm/s, and 45 cm/s, respectively.The examination of the above figures reveals that the radialgas holdup profiles in the 6tube bundle is always somewhathigher than the profile in columns of the same diameter withsolid walls. The average difference between the two is ∼15%while the maximum difference is only observed at the highestr/R. The latter was expected due to the interaction between theinside and outside of the tube bundle (note that in the current