Fig. 4b shows the variation of a/A as a function of Reynolds
number for different impellers in the unbaffled condition,
where a is the total cross-sectional area of the IMRs and A
is the cross-sectional area of the tank. It can be seen from the
figures that at a given Reynolds number, the disk impeller produced
the largest IMR structures, whereas the Rushton turbine
(DT6) had the smallest IMR structures. It must be pointed out
that further increase in Reynolds number for PR30 and Disk
exceeded the speed limit of the test rig (∼2000 rpm), thus the
a/A vs. Re data could only be obtained up to Re
∼
250 in the
current test set-up (Fig. 4b).