Turbulent Flow Impeller Mixer
Environmental Engineering · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Values of the Impeller Constant KT
- Note: Constant assumes baffled tanks having four baffles at the tank
- wall with a width equal to 10% of the tank diameter.
- Reprinted with permission from Industrial & Engineering Chemistry,
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
turbulent flow impeller mixer power requirement for rapid mix Given impeller constant (K_T) = 5.8500; fluid density (rho) = 995.0 kg/m^3; rotational speed (N) = 4.3000 rev/s; impeller diameter (D_i) = 0.5700 m, determine the power input (P) in W.
Given
impeller diameter (D_i) = 0.5700 m
Find
power input (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 1 — schematic for Turbulent Flow Impeller Mixer — solve for power input — Turbulent Flow Impeller Mixer
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: impeller constant (K_T) = 5.8500, fluid density (rho) = 995.0 kg/m^3, rotational speed (N) = 4.3000 rev/s, impeller diameter (D_i) = 0.5700 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 27,846 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 55,691 — kept a factor of two that cancels in the correct rearrangement.
- 13,923 — dropped that same factor in the other direction.
- 30,630 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer design in a coagulation basin Given impeller constant (K_T) = 3.7500; fluid density (rho) = 999.5 kg/m^3; impeller diameter (D_i) = 1.0200 m; power input (P) = 33,767 W, determine the rotational speed (N) in rev/s.
Given
impeller diameter (D_i) = 1.0200 m
Find
rotational speed (N), in rev/s
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except N is given, so isolate N symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 2 — schematic for Turbulent Flow Impeller Mixer — solve for rotational speed — Turbulent Flow Impeller Mixer (2)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: impeller constant (K_T) = 3.7500, fluid density (rho) = 999.5 kg/m^3, impeller diameter (D_i) = 1.0200 m, power input (P) = 33,767 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 2.0132 rev/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 4.0265 — kept a factor of two that cancels in the correct rearrangement.
- 1.0066 — dropped that same factor in the other direction.
- 2.2145 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent impeller flow mixer power calculation for flocculation Given impeller constant (K_T) = 2.0000; fluid density (rho) = 992.0 kg/m^3; rotational speed (N) = 0.8500 rev/s; power input (P) = 23,718 W, determine the impeller diameter (D_i) in m.
Given
Find
impeller diameter (D_i), in m
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except D_i is given, so isolate D_i symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 3 — schematic for Turbulent Flow Impeller Mixer — solve for impeller diameter — Turbulent Flow Impeller Mixer (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for D_i:
Step 3 — List the givens: impeller constant (K_T) = 2.0000, fluid density (rho) = 992.0 kg/m^3, rotational speed (N) = 0.8500 rev/s, power input (P) = 23,718 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning D_i = 1.8107 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.6215 — kept a factor of two that cancels in the correct rearrangement.
- 0.9054 — dropped that same factor in the other direction.
- 1.9918 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer power requirement for rapid mix Given impeller constant (K_T) = 1.0500; fluid density (rho) = 995.5 kg/m^3; rotational speed (N) = 1.7500 rev/s; impeller diameter (D_i) = 1.2100 m, determine the power input (P) in W.
Given
impeller diameter (D_i) = 1.2100 m
Find
power input (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 4 — schematic for Turbulent Flow Impeller Mixer — solve for power input (case 2) — Turbulent Flow Impeller Mixer (4)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: impeller constant (K_T) = 1.0500, fluid density (rho) = 995.5 kg/m^3, rotational speed (N) = 1.7500 rev/s, impeller diameter (D_i) = 1.2100 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 14,530 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 29,060 — kept a factor of two that cancels in the correct rearrangement.
- 7,265 — dropped that same factor in the other direction.
- 15,983 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer design in a coagulation basin Given impeller constant (K_T) = 0.7000; fluid density (rho) = 995.0 kg/m^3; impeller diameter (D_i) = 0.6700 m; power input (P) = 46,243 W, determine the rotational speed (N) in rev/s.
Given
impeller diameter (D_i) = 0.6700 m
Find
rotational speed (N), in rev/s
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except N is given, so isolate N symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 5 — schematic for Turbulent Flow Impeller Mixer — solve for rotational speed (case 2) — Turbulent Flow Impeller Mixer (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: impeller constant (K_T) = 0.7000, fluid density (rho) = 995.0 kg/m^3, impeller diameter (D_i) = 0.6700 m, power input (P) = 46,243 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 7.8931 rev/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 15.7863 — kept a factor of two that cancels in the correct rearrangement.
- 3.9466 — dropped that same factor in the other direction.
- 8.6825 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent impeller flow mixer power calculation for flocculation Given impeller constant (K_T) = 3.6500; fluid density (rho) = 999.5 kg/m^3; rotational speed (N) = 3.0000 rev/s; power input (P) = 32,887 W, determine the impeller diameter (D_i) in m.
Given
Find
impeller diameter (D_i), in m
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except D_i is given, so isolate D_i symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 6 — schematic for Turbulent Flow Impeller Mixer — solve for impeller diameter (case 2) — Turbulent Flow Impeller Mixer (6)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for D_i:
Step 3 — List the givens: impeller constant (K_T) = 3.6500, fluid density (rho) = 999.5 kg/m^3, rotational speed (N) = 3.0000 rev/s, power input (P) = 32,887 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning D_i = 0.8030 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.6060 — kept a factor of two that cancels in the correct rearrangement.
- 0.4015 — dropped that same factor in the other direction.
- 0.8833 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer power requirement for rapid mix Given impeller constant (K_T) = 4.9000; fluid density (rho) = 1,000 kg/m^3; rotational speed (N) = 0.9500 rev/s; impeller diameter (D_i) = 0.9900 m, determine the power input (P) in W.
Given
impeller diameter (D_i) = 0.9900 m
Find
power input (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 7 — schematic for Turbulent Flow Impeller Mixer — solve for power input (case 3) — Turbulent Flow Impeller Mixer (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: impeller constant (K_T) = 4.9000, fluid density (rho) = 1,000 kg/m^3, rotational speed (N) = 0.9500 rev/s, impeller diameter (D_i) = 0.9900 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 3,995 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 7,990 — kept a factor of two that cancels in the correct rearrangement.
- 1,998 — dropped that same factor in the other direction.
- 4,395 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer design in a coagulation basin Given impeller constant (K_T) = 0.7000; fluid density (rho) = 999.0 kg/m^3; impeller diameter (D_i) = 0.7600 m; power input (P) = 49,594 W, determine the rotational speed (N) in rev/s.
Given
impeller diameter (D_i) = 0.7600 m
Find
rotational speed (N), in rev/s
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except N is given, so isolate N symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 8 — schematic for Turbulent Flow Impeller Mixer — solve for rotational speed (case 3) — Turbulent Flow Impeller Mixer (8)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for N:
Step 3 — List the givens: impeller constant (K_T) = 0.7000, fluid density (rho) = 999.0 kg/m^3, impeller diameter (D_i) = 0.7600 m, power input (P) = 49,594 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning N = 6.5398 rev/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 13.0796 — kept a factor of two that cancels in the correct rearrangement.
- 3.2699 — dropped that same factor in the other direction.
- 7.1938 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent impeller flow mixer power calculation for flocculation Given impeller constant (K_T) = 3.5000; fluid density (rho) = 992.0 kg/m^3; rotational speed (N) = 0.5000 rev/s; power input (P) = 2,722 W, determine the impeller diameter (D_i) in m.
Given
Find
impeller diameter (D_i), in m
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except D_i is given, so isolate D_i symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 9 — schematic for Turbulent Flow Impeller Mixer — solve for impeller diameter (case 3) — Turbulent Flow Impeller Mixer (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for D_i:
Step 3 — List the givens: impeller constant (K_T) = 3.5000, fluid density (rho) = 992.0 kg/m^3, rotational speed (N) = 0.5000 rev/s, power input (P) = 2,722 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning D_i = 1.4437 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.8874 — kept a factor of two that cancels in the correct rearrangement.
- 0.7219 — dropped that same factor in the other direction.
- 1.5881 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer
turbulent flow impeller mixer power requirement for rapid mix Given impeller constant (K_T) = 4.7500; fluid density (rho) = 993.0 kg/m^3; rotational speed (N) = 1.6500 rev/s; impeller diameter (D_i) = 0.2200 m, determine the power input (P) in W.
Given
impeller diameter (D_i) = 0.2200 m
Find
power input (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Turbulent Flow Impeller Mixer.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A turbulent flow impeller mixer requires power proportional to impeller speed and diameter for rapid mixing in a basin.
Figure 10 — schematic for Turbulent Flow Impeller Mixer — solve for power input (case 4) — Turbulent Flow Impeller Mixer (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: impeller constant (K_T) = 4.7500, fluid density (rho) = 993.0 kg/m^3, rotational speed (N) = 1.6500 rev/s, impeller diameter (D_i) = 0.2200 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 10.9196 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 21.8393 — kept a factor of two that cancels in the correct rearrangement.
- 5.4598 — dropped that same factor in the other direction.
- 12.0116 — rounded an intermediate value before the final step.
Reference: FE Handbook — Turbulent Flow Impeller Mixer