ANS:B - Helical screw

The agitator that is typically used for mixing high viscosity liquids (greater than 50000 centipoise) with a large blade area and rotating at a slow speed is the Flat Blade Turbine.

Explanation:

• Flat Blade Turbine: This type of agitator is designed with flat blades that provide a large surface area relative to the volume being mixed. It operates effectively at slow speeds to handle high viscosity fluids.
• Characteristics:
  • Large Blade Area: The flat blades of this turbine agitator create significant surface contact with the liquid, promoting efficient mixing and circulation.
  • Slow Speed: It rotates at slower speeds to prevent excessive shear and turbulence, which can be detrimental in high viscosity liquids.
  • Applications: Ideal for mixing applications where the viscosity of the liquid exceeds 50000 centipoise (cP), such as in the chemical, food processing, and pharmaceutical industries.
• Other Agitators:
  • Propeller: Generally used for low to medium viscosity fluids due to its high-speed mixing capability.
  • Helical Screw: Also known as ribbon agitators, used for viscous materials but may not handle very high viscosity liquids as effectively as flat blade turbines.
  • Curved Blade Turbine: Suitable for a wide range of viscosities but typically used in moderate viscosity applications.