Fluid Shear Rates, Impeller Pumping Capacity and Power Consumption

2 Fluid Shear Rates, Impeller Pumping Capacity and Power Consumption 

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Fluid Shear Rates, Impeller Pumping Capacity and Power Consumption 689 h = r X (mv) [kgrti /s) (7-8)... 

On the left-hand side, visual descriptions of flow patterns and other types of descriptions of the flow patterns are helpful and important in establishing the effect of mixing variables on these criteria. In general, they are characterized by a requirement for high pumping capacity rather than fluid shear rate, and studies to optimize the pumping capacity of the impellers relative to power consumption are fruitful. 

The power consumption of an impeller is the product of the pumping capacity (circulation fiow rate) and the velocity head, which is directly related to shear rate and turbulence. Depending on the type and size of the impeller, either the flow or the turbulence can be favored [110]. Axial flow impellers usually produce a fluid motion that is downward at the central axis of the vessel and upward in the wall region. They are designed to produce a high flow/power ratio with little turbulent loss. The designs of axial-flow impellers are derived from three-blade propellers. Radial-flow turbines produce a radial fluid motion from the impeller to the wall, where the radial flow separates into an upper and a lower circulation loop. They are characterized by a relatively low flow/power ratio, with much of the energy dissipated by turbulence around the impeller. Radial-flow turbines have flat blades or a disk with flat blades. 

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