**14. Validation of the computational model**

The experimental mixing curves for Monitor C (Tracer 1) and E (Tracer 2) were obtained from pH data plots against time. Experimental and simulation data are compared in **Figure 17**.

**Figure 17.** Comparison of experimental data (**Δ**,×) and numerically (—) obtained solutions.

Simulated curves in **Figure 17** were obtained at a stirrer speed of 100 rpm with liquid water, using MRF and realizable *k-* as working models. The injections were made in the regions established in **Figure 12**.

The mixing time for tracer 1 has a value of 15.4 s and for tracer 2, a total of 35.8 s (**Figures 18** and **19**). The criterion used to define the mixing time was the standard deviation of the concentration data registered in all monitors [26].

**Figure 18.** Standard deviation of data from MRF model at 100 rpm.

**Table 5.** Mass fraction of tracer dispersion at different times.

286 Modeling and Simulation in Engineering Sciences

established in **Figure 12**.

**14. Validation of the computational model**

**Figure 17.** Comparison of experimental data (**Δ**,×) and numerically (—) obtained solutions.

The experimental mixing curves for Monitor C (Tracer 1) and E (Tracer 2) were obtained from pH data plots against time. Experimental and simulation data are compared in **Figure 17**.

Simulated curves in **Figure 17** were obtained at a stirrer speed of 100 rpm with liquid water, using MRF and realizable *k-* as working models. The injections were made in the regions

**Figure 19.** Mixing times of tracer 1 and tracer 2 (all monitors).

The experimental and numerical mixing times are shown in **Table 6**. The mixing time in Monitor C differs from the experimental value by 5 seconds, while Monitor E differs from it by 0.1 seconds. The resemblance between Monitors B-C and D-E is due to their spatial position.


**Table 6.** Simulated and experimental mixing times for tracer 1 and 2.

The injection zone 1 (Tracer 1) allows a lower mixing time compared with the injection zone 2. However, mixing times of Monitors C and E are less sensitive to changes in stirrer speed.

The SM and ROT stirring models were discarded because the calculated mixing time does not correspond to the experimental data, as seen in **Figures 20** and **21**. Experimental mixing time is well fitted by MRF calculations.

**Figure 20.** Tracer 1 curves, Monitor C (100 rpm) with 3 different models: MRF, SM, and ROT.

**Figure 21.** Tracer 2 curves, Monitor E (100 rpm) with 3 different models: MRF, SM, and ROT.

## **15. Effect of the stirring speed**

Once MRF model was selected, a stirring speed swept from 100 to 300 rpm was done. Monitor C mixing time presents minor variations between 100 to 200 rpm; however, at 300 rpm the mixing time is drastically reduced (**Figure 22**). In contrast, in Monitor E the mixing time is reduced by increasing the stirring speed. An increase in the stirring speed leads to a reduced mixing time, allowing better contact among chemical species. Nevertheless, in the case of polymerization, a high stirring speed (above 300 rpm) can produce mechanical degradation of the formed chains.

**Figure 22.** MRF simulated mixing times at 100, 200 and 300 rpm.
