Mechanically radial flow impeller

There are four types of turbine impellers, which are characterized by the flow patterns and level of shear they create axial flow, radial flow, hydrofoil, and high-shear impellers. They have the widest use in low and medium viscosity liquid applications, solids suspension, liquid-liquid emulsification, and gas dispersion. Turbine impellers can have blades varying from 2 to 12 in number. Two blades are normally unstable mechanically, while it is difficult to install more than six blades on a hub. Axial flow impellers generally have three or four blades, and radial flow impellers are designed with six blades. 

Although low shear emulsification equipment (mechanical stirrers or impellers) can differ in the type of fluid flow imparted to the mixture (axial-flow propeller or radial-flow turbines), no subclasses have been defined. 

The impeller blades are usually mounted at a height between 0.25 and 0.5 of the height of the liquid layer. The diameter of the impeller conunonly varies between 0.2 and 0.5 of the tank diameter a diameter ratio of 1/3 is often preferred. The tanks are usually equipped with baffles (most often four), flat plates of a width of about 0.1 of the tank diameter, mounted vertically along the walls. These baffles serve to reduce liquid circulation around the axis and so to avoid the formation of a vortex in the middle they also promote vertical circulation. Propellers are usually made so that they pump downwards, as a result of which there is a liquid flow going up near the wall. Turbine impellers pump radially, so that in the lower half of the tank the liquid circulates downwards near the wall and upwards in the middle, and in the upper half the other way around. In some respects there is no important difference between these two types of impellers. Both create an effective circulation, and in both cases most of the supplied mechanical energy is eventually dissipated in small eddies. The friction losses at the wall and at the impeller blades are a relatively small fraction of the total energy dissipation. 

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