Principle, Construction, Working, Uses, Merits and Demerits of Turbines

Turbines

Principle

Due to the combination of centrifugal and rotational movement, turbine mixer agitators can create turbulent movements of fluids. This will effectively mix low to medium viscosity fluids.

Construction

There is a wide range of turbine designs, shown in figure below. They usually consist of a circle with several short blades attached. Turbine diameters differ from propeller diameters by 0.13-0.57, with 0.33:1 being the most common. Flat blade turbines produce radial and tangential flow, but as speed increases, radial flow takes over. Blade design may be straight, pitched, curved, or disk type. The turbine rotates slower, usually between 50 and 200 rpm, than propellers. Pitch bladed turbines produce axial flow, which demonstrates high turbulence and intense shear at the impeller zone. Diffuser rings are used to further enhance turbine shear. Turbines are enclosed in a stationary ring of perforated metal called a diffuser ring.

Working

With a mixing blade, a drum or pan is filled with material. The variable speed drill with a turbine mixer whirls air into the mixture as it revolves. Several different turbines and impellers are included in the top entry turbine mixer to handle both heat and mass transfer of liquids and solids. The product does not get damaged when using this type of mixer. A top-entry high-shear mixer emulsifies and homogenizes materials uniformly. The mixing blades revolve about a vertical axis.

Uses

• Extraction and chemical reactions are highly used methods. Chemical reactions in liquids and gases, for instance.
• A liquid used for preparing suspensions, emulsions, and syrups.

Merits

• Emulsification is performed with turbines because their high shearing forces allow them to produce a higher pumping rate even at low pumping rates.
• Despite its high viscosity, these mixers can mix high viscous solutions of up to 7.0 Pa.s.
• Dispersion containing 60% solids can be made with them.
• With the addition of baffles in the tank, turbines can handle liquids of large volume and high viscosity.
• The mixing efficiency is high since they generate high radial flows.
• Low viscous materials with large volumes are used with a turbine, which eliminates stagnant pockets by producing a strong current.

Demerits

• Solvents with a viscosity greater than 20 cP should not be used with these filters.
• Mixing materials in an enclosed space may result in oxidation due to air entrapment.

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