Blowers
Fluid Mechanics · FE Reference Handbook section
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.
blowers used for aeration in a wastewater basin Given weight flow rate (w) = 1.5000 N/s; actual inlet temperature ratio factor (Q) = 1.0000; discharge pressure (p_2) = 227.0 kPa; inlet pressure (p_1) = 97.0000 kPa; efficiency (e) = 0.6100, determine the blower power (P) in kW.
Given
actual inlet temperature ratio factor (Q) = 1.0000
Find
blower power (P), in kW
Start with the thinking
- The governing relation printed in this handbook section is Blowers (adiabatic power).
- 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.
- Blowers deliver air at modest pressure rise, and their power is estimated from an adiabatic compression relation.
Figure 1 — schematic for Blowers (adiabatic power) — solve for blower power — Blowers
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that P stands alone on the left-hand side.
Step 3 — List the givens: weight flow rate (w) = 1.5000 N/s, actual inlet temperature ratio factor (Q) = 1.0000, discharge pressure (p_2) = 227.0 kPa, inlet pressure (p_1) = 97.0000 kPa, efficiency (e) = 0.6100.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning P = 0.0225 kW to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0450 — kept a factor of two that cancels in the correct rearrangement.
- 0.0113 — dropped that same factor in the other direction.
- 0.0248 — rounded an intermediate value before the final step.
Reference: FE Handbook — Blowers
a centrifugal blower on a dust-collection duct Given volumetric flow (Q) = 8.8000 m^3/s; pressure rise (\Delta p) = 22,500 Pa; efficiency (\eta) = 0.5900, determine the shaft power (W) in W.
Given
Find
shaft power (W), in W
Start with the thinking
- The governing relation printed in this handbook section is Blower / compressor fluid power.
- Everything except W is given, so isolate W 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 blower raises the pressure of an air stream across an aeration basin diffuser system.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for W:
Step 3 — List the givens: volumetric flow (Q) = 8.8000 m^3/s, pressure rise (\Delta p) = 22,500 Pa, efficiency (\eta) = 0.5900.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning W = 335,593 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 671,186 — kept a factor of two that cancels in the correct rearrangement.
- 167,797 — dropped that same factor in the other direction.
- 369,153 — rounded an intermediate value before the final step.
Reference: FE Handbook — Fans, Blowers, and Compressors
blowers supplying combustion air at low pressure rise Given weight flow rate (w) = 12.5000 N/s; actual inlet temperature ratio factor (Q) = 1.0000; discharge pressure (p_2) = 164.0 kPa; inlet pressure (p_1) = 97.5000 kPa; blower power (P) = 104.0 kW, determine the efficiency (e).
Given
actual inlet temperature ratio factor (Q) = 1.0000
Find
efficiency (e)
Start with the thinking
- The governing relation printed in this handbook section is Blowers (adiabatic power).
- Everything except e is given, so isolate e 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.
- Blowers deliver air at modest pressure rise, and their power is estimated from an adiabatic compression relation.
Figure 3 — schematic for Blowers (adiabatic power) — solve for efficiency — Blowers (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that e stands alone on the left-hand side.
Step 3 — List the givens: weight flow rate (w) = 12.5000 N/s, actual inlet temperature ratio factor (Q) = 1.0000, discharge pressure (p_2) = 164.0 kPa, inlet pressure (p_1) = 97.5000 kPa, blower power (P) = 104.0 kW.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning e = 0.0006 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0013 — kept a factor of two that cancels in the correct rearrangement.
- 0.0003 — dropped that same factor in the other direction.
- 0.0007 — rounded an intermediate value before the final step.
Reference: FE Handbook — Blowers
a compressor supplying pneumatic construction tools Given shaft power (W) = 176,326 W; pressure rise (\Delta p) = 38,800 Pa; efficiency (\eta) = 0.6900, determine the volumetric flow (Q) in m^3/s.
Given
Find
volumetric flow (Q), in m^3/s
Start with the thinking
- The governing relation printed in this handbook section is Blower / compressor fluid power.
- Everything except Q is given, so isolate Q 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 blower raises the pressure of an air stream across an aeration basin diffuser system.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: shaft power (W) = 176,326 W, pressure rise (\Delta p) = 38,800 Pa, efficiency (\eta) = 0.6900.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Q = 3.1357\ \text{m^3/s}Step 6 — Check: returning Q = 3.1357 m^3/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6.2714 — kept a factor of two that cancels in the correct rearrangement.
- 1.5678 — dropped that same factor in the other direction.
- 3.4493 — rounded an intermediate value before the final step.
Reference: FE Handbook — Fans, Blowers, and Compressors
blowers moving air through ductwork at elevated pressure Given weight flow rate (w) = 4.0000 N/s; actual inlet temperature ratio factor (Q) = 1.0000; discharge pressure (p_2) = 195.0 kPa; inlet pressure (p_1) = 95.5000 kPa; efficiency (e) = 0.8700, determine the blower power (P) in kW.
Given
actual inlet temperature ratio factor (Q) = 1.0000
Find
blower power (P), in kW
Start with the thinking
- The governing relation printed in this handbook section is Blowers (adiabatic power).
- 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.
- Blowers deliver air at modest pressure rise, and their power is estimated from an adiabatic compression relation.
Figure 5 — schematic for Blowers (adiabatic power) — solve for blower power (case 2) — Blowers (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that P stands alone on the left-hand side.
Step 3 — List the givens: weight flow rate (w) = 4.0000 N/s, actual inlet temperature ratio factor (Q) = 1.0000, discharge pressure (p_2) = 195.0 kPa, inlet pressure (p_1) = 95.5000 kPa, efficiency (e) = 0.8700.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning P = 0.0347 kW to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0693 — kept a factor of two that cancels in the correct rearrangement.
- 0.0173 — dropped that same factor in the other direction.
- 0.0381 — rounded an intermediate value before the final step.
Reference: FE Handbook — Blowers
a positive-displacement blower feeding an aeration basin Given shaft power (W) = 102,017 W; volumetric flow (Q) = 10.4000 m^3/s; pressure rise (\Delta p) = 20,500 Pa, determine the efficiency (\eta).
Given
Find
efficiency (\eta)
Start with the thinking
- The governing relation printed in this handbook section is Blower / compressor fluid power.
- Everything except \eta is given, so isolate \eta 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 blower raises the pressure of an air stream across an aeration basin diffuser system.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for \eta:
Step 3 — List the givens: shaft power (W) = 102,017 W, volumetric flow (Q) = 10.4000 m^3/s, pressure rise (\Delta p) = 20,500 Pa.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning \eta = 2.0898 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 4.1797 — kept a factor of two that cancels in the correct rearrangement.
- 1.0449 — dropped that same factor in the other direction.
- 2.2988 — rounded an intermediate value before the final step.
Reference: FE Handbook — Fans, Blowers, and Compressors
blowers used for aeration in a wastewater basin Given weight flow rate (w) = 19.0000 N/s; actual inlet temperature ratio factor (Q) = 1.0000; discharge pressure (p_2) = 162.0 kPa; inlet pressure (p_1) = 97.0000 kPa; blower power (P) = 174.0 kW, determine the efficiency (e).
Given
actual inlet temperature ratio factor (Q) = 1.0000
Find
efficiency (e)
Start with the thinking
- The governing relation printed in this handbook section is Blowers (adiabatic power).
- Everything except e is given, so isolate e 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.
- Blowers deliver air at modest pressure rise, and their power is estimated from an adiabatic compression relation.
Figure 7 — schematic for Blowers (adiabatic power) — solve for efficiency (case 2) — Blowers (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that e stands alone on the left-hand side.
Step 3 — List the givens: weight flow rate (w) = 19.0000 N/s, actual inlet temperature ratio factor (Q) = 1.0000, discharge pressure (p_2) = 162.0 kPa, inlet pressure (p_1) = 97.0000 kPa, blower power (P) = 174.0 kW.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning e = 0.0006 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.0011 — kept a factor of two that cancels in the correct rearrangement.
- 0.0003 — dropped that same factor in the other direction.
- 0.0006 — rounded an intermediate value before the final step.
Reference: FE Handbook — Blowers
a centrifugal blower on a dust-collection duct Given volumetric flow (Q) = 3.8000 m^3/s; pressure rise (\Delta p) = 34,200 Pa; efficiency (\eta) = 0.6000, determine the shaft power (W) in W.
Given
Find
shaft power (W), in W
Start with the thinking
- The governing relation printed in this handbook section is Blower / compressor fluid power.
- Everything except W is given, so isolate W 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 blower raises the pressure of an air stream across an aeration basin diffuser system.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for W:
Step 3 — List the givens: volumetric flow (Q) = 3.8000 m^3/s, pressure rise (\Delta p) = 34,200 Pa, efficiency (\eta) = 0.6000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning W = 216,600 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 433,200 — kept a factor of two that cancels in the correct rearrangement.
- 108,300 — dropped that same factor in the other direction.
- 238,260 — rounded an intermediate value before the final step.
Reference: FE Handbook — Fans, Blowers, and Compressors
blowers supplying combustion air at low pressure rise Given weight flow rate (w) = 8.5000 N/s; actual inlet temperature ratio factor (Q) = 1.0000; discharge pressure (p_2) = 192.0 kPa; inlet pressure (p_1) = 98.5000 kPa; efficiency (e) = 0.7800, determine the blower power (P) in kW.
Given
actual inlet temperature ratio factor (Q) = 1.0000
Find
blower power (P), in kW
Start with the thinking
- The governing relation printed in this handbook section is Blowers (adiabatic power).
- 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.
- Blowers deliver air at modest pressure rise, and their power is estimated from an adiabatic compression relation.
Figure 9 — schematic for Blowers (adiabatic power) — solve for blower power (case 3) — Blowers (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that P stands alone on the left-hand side.
Step 3 — List the givens: weight flow rate (w) = 8.5000 N/s, actual inlet temperature ratio factor (Q) = 1.0000, discharge pressure (p_2) = 192.0 kPa, inlet pressure (p_1) = 98.5000 kPa, efficiency (e) = 0.7800.
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning P = 0.0763 kW to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.1526 — kept a factor of two that cancels in the correct rearrangement.
- 0.0381 — dropped that same factor in the other direction.
- 0.0839 — rounded an intermediate value before the final step.
Reference: FE Handbook — Blowers
a compressor supplying pneumatic construction tools Given shaft power (W) = 181,731 W; pressure rise (\Delta p) = 16,700 Pa; efficiency (\eta) = 0.8100, determine the volumetric flow (Q) in m^3/s.
Given
Find
volumetric flow (Q), in m^3/s
Start with the thinking
- The governing relation printed in this handbook section is Blower / compressor fluid power.
- Everything except Q is given, so isolate Q 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 blower raises the pressure of an air stream across an aeration basin diffuser system.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: shaft power (W) = 181,731 W, pressure rise (\Delta p) = 16,700 Pa, efficiency (\eta) = 0.8100.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Q = 8.8145\ \text{m^3/s}Step 6 — Check: returning Q = 8.8145 m^3/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 17.6290 — kept a factor of two that cancels in the correct rearrangement.
- 4.4072 — dropped that same factor in the other direction.
- 9.6959 — rounded an intermediate value before the final step.
Reference: FE Handbook — Fans, Blowers, and Compressors