Experimental results

For each configuration, the power number is measured for different angular velocities ($80$, $100$, $120$, $140$, $160$, $180$ and $200~RPM$). Tables 2.3, 2.4 and  2.5 gather obtained results.

Table 2.3: Experimental power number data for single beaver-tail baffle.

Single beaver-tail baffle
RPM	$Ne$
	Glycerol	Water-Glycerol solution	Water
80	0.931	0.700	0.532
100	1.062	0.703	0.596
120	0.946	0.665	0.591
140	1.021	0.684	0.565
160	0.981	0.724	0.532
180	1.012	0.651	0.539
200	0.947	0.655	0.500

Table 2.4: Experimental power number data for two beaver-tail baffles.

Two beaver-tail baffles
RPM	$Ne$
	Glycerol	Water-Glycerol solution	Water
80	1.059	0.826	0.660
100	1.061	0.912	0.806
120	1.092	0.810	0.737
140	0.997	0.595	0.672
160	0.963	0.755	0.714
180	0.879	0.715	0.643
200	0.904	0.771	0.648

Table 2.5: Experimental power number data for single finger baffle.

Single finger baffle
RPM	$Ne$
	Glycerol	Water-Glycerol solution	Water
80	0.940	0.651	0.611
100	1.112	0.672	0.646
120	0.950	0.644	0.660
140	0.828	0.734	0.655
160	0.933	0.662	0.552
180	1.014	0.641	0.633
200	0.949	0.647	0.608

The experimental power numbers measured for each configuration are compared against those calculated using the empirical correlations developed by Nagata (1975). Power characteristics calculated for the single beaver-tail baffle configuration, the two beaver-tail baffles configuration and the single finger baffle configuration are shown in Figure 2.2. The curve derived from the published material given by Tycon $-$ Technoglass is also reported as reference curve. Comparison between empirical curves and experimental data is shown in Figure 2.3, 2.4 and 2.5 for the single beaver-tail baffle configuration, the two beaver-tail baffles configuration and the single finger baffle configuration, respectively.

Figure 2.2: Power number versus Reynolds number: power characteristics calculated from Nagata (1975) for different configurations examined for laboratory tank.

Figure 2.3: Power number versus Reynolds number: power characteristic calculated from Nagata (1975) and experimental points for laboratory tank with single beaver-tail baffle.

Figure 2.4: Power number versus Reynolds number: power characteristic calculated from Nagata (1975) and experimental points for laboratory tank with two beaver-tail baffles.

Figure 2.5: Power number versus Reynolds number: power characteristic calculated from Nagata (1975) and experimental points for laboratory tank with single finger baffle.

The calculation of the power characteristics is made following the procedure described in Appendix B: geometrical parameters of the CSTR are used to calculate dimensionless geometrical ratios and the parameters of the power characteristics are then derived from available correlations. To calculate the empirical curve for the single finger baffle configuration, an equivalent baffle width equal to $33~mm$ is used. This equivalent width is obtained averaging the width of the baffle over the vertical, weighted on the azimuthal velocity profile obtained from numerical simulations. A curve lying in between the single and two beaver-tail baffles configurations is obtained. Experimental results are in good agreement with empirical curves. Deviations between experimental data and empirically derived power characteristic are observed at lower Reynolds numbers. A little scatter of experimental data can also be observed at both high and low Reynolds range.