The agitation is achieved by movement of the heterogeneous mass (liquid-solid phase).
The bulk can be composed of different substances and the aim of the operation is to blend it or to improve the efficiency of a reaction by a better contact between reactive product.
Agitation may also be used to increase heat transfer or to maintain particles in suspension.
Depending on its shape, the impeller can generate: These two phenomena provide energy consumption.
Turbines (flat blades or pitched blades) which inlet flow is axial and outlet flow is radial will provide shearing, turbulence and need approximately 20 time more energy than propellers, for the same diameter and same rotation speed.