Results and discussion
In the segregation experiments, the sampling location was set with a
distance away from the inlet of acid injection. In order to guarantee
that a well-established micromixing process is achieved throughout the
whole reactor, the collection time after acid injection should be
determined in advance. The preliminary experiment was performed at a
Reynolds number of 12564 in the CTC. It can be seen from Figure 3 that
the critical collection time is 120 s after finishing the injection of
acid. However, within the range from 90 s to 240 s, the results used to
determine the collection time also appear to be acceptable. One can
argue that if the collection time is too short, the macromixing has not
been fully achieved, thus resulting in little amount of the product
being detected at the outlet. On the other hand, if the collection time
is too long, the UV result may lose its accuracy since \(I_{3}^{-}\) is
very sensitive to light. Therefore, the determination of the critical
collection time is crucial for acquiring reliable results. It should be
noted that for different operating conditions, the critical collection
time may be different within the acceptable range. The following
discussion on the micromixing in the TC reactor with two different inner
cylinder configurations will be based on the samples collected at the
critical collection time determined for the CTC and LTC, respectively.