In industrial mixing, which application is the helical screw agitator best suited for?\nSelect the scenario that matches its typical use.

Introduction / Context:
Choosing the right impeller or agitator is critical in chemical, polymer, and food processing. The helical screw (also called helical ribbon) agitator is a specialty device for moving extremely viscous materials that conventional turbines cannot handle effectively.

Given Data / Assumptions:

• Process fluid is highly viscous (pastes, gels, doughs, creams).
• Goal: bulk circulation with minimal dead zones in a tank.
• Helical screw/ribbon agitators sweep close to the tank wall.

Concept / Approach:
At high viscosity, inertial effects diminish and laminar flow dominates. Standard propellers lose efficiency because they rely on turbulence. Helical screw agitators create axial and radial flow in laminar regimes by physically conveying material along the vessel wall and back through the core, ensuring turnover without excessive shear heating.

Step-by-Step Solution:

Verification / Alternative check:
Industry practice confirms ribbon/helical screw mixers in adhesive compounding, battery pastes, plastisols, sealants, and dough mixing, which are all high-viscosity duties.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming temperature dictates impeller choice; ignoring laminar vs turbulent regime; or selecting high-speed propellers for pastes (inefficient and heat-intensive).

Final Answer:
Mixing highly viscous pastes