might be strengthened. Lu and Ju (1987) measured quantitatively the distribution of the mean velocity and turbulence intensity in the impeller discharge stream region of an aerated stirred tank using a conical hot-film probe CTA (constant temperature ane- mometry), and they found that the mean velocity at a constant impeller speed was reduced against growing aeration number and the turbulence intensity increased with increasing aeration rate. This means the gas phase affects the liquid flow in a complex way, which further illustrates that the gas phase can either increase or decrease the liquid mixing depending on its magnitude.
3.2.8. Effect of physical property of dispersed phase
Fig. 10 presents a set of experiments using the Rushton impeller with various oils. The physical properties of three dispersed oil phases can be seen in Table 2. The mixing time increases slightly by 7.9% with aeration and by 8.9% in the absence of gas when the dispersed oil is changed from kerosene (2.0mPa.s) to methyl silicone oil (565 mPa.s). The increase in mixing time is mainly attributed to higher effective viscosity as explained by Zhao et al. (2011). Einsele and Finn (1980) measured the liquid mixing time in gas–liquid systems, and revealed that the mixing time increased with higher liquid viscosity.