For a turbine agitator installed in a tank of diameter d, the typical impeller diameter range used in design is:

Introduction / Context:
Turbine agitators are radial-flow impellers commonly used for gas dispersion, liquid blending, and solid suspension. Selecting an appropriate impeller diameter relative to tank diameter ensures efficient power draw and mixing without excessive shear or mechanical penalties.

Given Data / Assumptions:

• Cylindrical tank diameter = d.
• Standard six-blade Rushton or similar turbine.
• No unusual baffle or multiple-impeller special cases considered.

Concept / Approach:
Empirical mixer design practice places turbine impellers in the range of roughly one-third to one-half of tank diameter to balance flow circulation, tip speed, and power number. Much larger impellers approach the tank wall causing inefficient flow; much smaller impellers underutilize the volume.

Step-by-Step Solution:
Identify accepted design range for turbine impellers.Use rule of thumb: D_impeller ≈ 0.3 d to 0.5 d.Therefore, the correct answer is 0.3 to 0.5 d.

Verification / Alternative check:
Mixing handbooks and vendor guidelines routinely recommend roughly 0.33 d to 0.5 d for single-stage turbines in baffled tanks.

Why Other Options Are Wrong:
0.1–0.2 d: too small; poor circulation and long blend times.0.65–0.85 d or 0.95 d: too large; wall interference and excessive power draw.0.05–0.08 d: far too small for practical mixing.

Common Pitfalls:
Forgetting to adjust diameter when multiple impellers are installed at different elevations.Ignoring baffles; unbaffled tanks require different considerations.

Final Answer:
0.3 to 0.5 d