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Flow Through a Packed Bed

Fluid Mechanics · FE Reference Handbook section

Fluid Mechanics
11 formulas
10 exam-style examples
~60 min
All Fluid Mechanics lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • A porous, fixed bed of solid particles can be characterized by
  • The Ergun equation can be used to estimate pressure loss through a packed bed under laminar and turbulent flow conditions.
  • Submerged Orifice Operating under Steady-Flow Conditions:
  • in which the product of Cc and Cv is defined as the coefficient of discharge of the orifice.

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.

Example 1
Flow through a packed bed (Ergun-type head loss) — solve for head loss — Flow Through a Packed Bed

flow through a packed bed of granular filter media Given dynamic viscosity (mu) = 0.0006 Pa*s; bed porosity (epsilon) = 0.3100; superficial velocity (V) = 0.0360 m/s; gravity (g) = 9.7400 m/s^2; fluid density (rho) = 820.0 kg/m^3; particle diameter (D_p) = 0.0028 m; bed depth (L) = 1.2000 m, determine the head loss (h_f) in m.

Given

  • dynamicviscosity(mu)=0.0006Pa∗sdynamic viscosity (mu) = 0.0006 Pa*s
  • bedporosity(epsilon)=0.3100bed porosity (epsilon) = 0.3100
  • superficialvelocity(V)=0.0360m/ssuperficial velocity (V) = 0.0360 m/s
  • gravity(g)=9.7400m/s2gravity (g) = 9.7400 m/s^2
  • fluiddensity(rho)=820.0kg/m3fluid density (rho) = 820.0 kg/m^3
  • particlediameter(Dp)=0.0028mparticle diameter (D_p) = 0.0028 m
  • beddepth(L)=1.2000mbed depth (L) = 1.2000 m

Find

head loss (h_f), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except h_f is given, so isolate h_f 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0006 Pa*s, bed porosity (epsilon) = 0.3100, superficial velocity (V) = 0.0360 m/s, gravity (g) = 9.7400 m/s^2, fluid density (rho) = 820.0 kg/m^3, particle diameter (D_p) = 0.0028 m, bed depth (L) = 1.2000 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=0.9923 mh_{f} = 0.9923\ \text{m}
  6. Step 6 — Check: returning h_f = 0.9923 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=0.9923 mh_{f} = 0.9923\ \text{m}

Why the other options are there

  • 1.9846 — kept a factor of two that cancels in the correct rearrangement.
  • 0.4962 — dropped that same factor in the other direction.
  • 1.0915 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 2
Flow through a packed bed (Ergun-type head loss) — solve for superficial velocity — Flow Through a Packed Bed (2)

flow through a packed bed reactor with spherical particles Given dynamic viscosity (mu) = 0.0017 Pa*s; bed porosity (epsilon) = 0.3100; gravity (g) = 9.8300 m/s^2; fluid density (rho) = 1,030 kg/m^3; particle diameter (D_p) = 0.0068 m; bed depth (L) = 0.4000 m; head loss (h_f) = 3.3580 m, determine the superficial velocity (V) in m/s.

Given

  • dynamicviscosity(mu)=0.0017Pa∗sdynamic viscosity (mu) = 0.0017 Pa*s
  • bedporosity(epsilon)=0.3100bed porosity (epsilon) = 0.3100
  • gravity(g)=9.8300m/s2gravity (g) = 9.8300 m/s^2
  • fluiddensity(rho)=1,030kg/m3fluid density (rho) = 1,030 kg/m^3
  • particlediameter(Dp)=0.0068mparticle diameter (D_p) = 0.0068 m
  • beddepth(L)=0.4000mbed depth (L) = 0.4000 m
  • headloss(hf)=3.3580mhead loss (h_f) = 3.3580 m

Find

superficial velocity (V), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except V is given, so isolate V 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that V stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0017 Pa*s, bed porosity (epsilon) = 0.3100, gravity (g) = 9.8300 m/s^2, fluid density (rho) = 1,030 kg/m^3, particle diameter (D_p) = 0.0068 m, bed depth (L) = 0.4000 m, head loss (h_f) = 3.3580 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    V=0.9644 m/sV = 0.9644\ \text{m/s}
  6. Step 6 — Check: returning V = 0.9644 m/s to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
V=0.9644 m/sV = 0.9644\ \text{m/s}

Why the other options are there

  • 1.9289 — kept a factor of two that cancels in the correct rearrangement.
  • 0.4822 — dropped that same factor in the other direction.
  • 1.0609 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 3
Flow through a packed bed (Ergun-type head loss) — solve for bed depth — Flow Through a Packed Bed (3)

flow through a packed bed used in a water treatment column Given dynamic viscosity (mu) = 0.0008 Pa*s; bed porosity (epsilon) = 0.5200; superficial velocity (V) = 0.0480 m/s; gravity (g) = 9.7900 m/s^2; fluid density (rho) = 1,050 kg/m^3; particle diameter (D_p) = 0.0040 m; head loss (h_f) = 1.6330 m, determine the bed depth (L) in m.

Given

  • dynamicviscosity(mu)=0.0008Pa∗sdynamic viscosity (mu) = 0.0008 Pa*s
  • bedporosity(epsilon)=0.5200bed porosity (epsilon) = 0.5200
  • superficialvelocity(V)=0.0480m/ssuperficial velocity (V) = 0.0480 m/s
  • gravity(g)=9.7900m/s2gravity (g) = 9.7900 m/s^2
  • fluiddensity(rho)=1,050kg/m3fluid density (rho) = 1,050 kg/m^3
  • particlediameter(Dp)=0.0040mparticle diameter (D_p) = 0.0040 m
  • headloss(hf)=1.6330mhead loss (h_f) = 1.6330 m

Find

bed depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except L is given, so isolate L 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0008 Pa*s, bed porosity (epsilon) = 0.5200, superficial velocity (V) = 0.0480 m/s, gravity (g) = 9.7900 m/s^2, fluid density (rho) = 1,050 kg/m^3, particle diameter (D_p) = 0.0040 m, head loss (h_f) = 1.6330 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=28.4566 mL = 28.4566\ \text{m}
  6. Step 6 — Check: returning L = 28.4566 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=28.4566 mL = 28.4566\ \text{m}

Why the other options are there

  • 56.9132 — kept a factor of two that cancels in the correct rearrangement.
  • 14.2283 — dropped that same factor in the other direction.
  • 31.3023 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 4
Flow through a packed bed (Ergun-type head loss) — solve for head loss (case 2) — Flow Through a Packed Bed (4)

flow through a packed bed of granular filter media Given dynamic viscosity (mu) = 0.0016 Pa*s; bed porosity (epsilon) = 0.3100; superficial velocity (V) = 0.0250 m/s; gravity (g) = 9.8200 m/s^2; fluid density (rho) = 870.0 kg/m^3; particle diameter (D_p) = 0.0086 m; bed depth (L) = 2.7500 m, determine the head loss (h_f) in m.

Given

  • dynamicviscosity(mu)=0.0016Pa∗sdynamic viscosity (mu) = 0.0016 Pa*s
  • bedporosity(epsilon)=0.3100bed porosity (epsilon) = 0.3100
  • superficialvelocity(V)=0.0250m/ssuperficial velocity (V) = 0.0250 m/s
  • gravity(g)=9.8200m/s2gravity (g) = 9.8200 m/s^2
  • fluiddensity(rho)=870.0kg/m3fluid density (rho) = 870.0 kg/m^3
  • particlediameter(Dp)=0.0086mparticle diameter (D_p) = 0.0086 m
  • beddepth(L)=2.7500mbed depth (L) = 2.7500 m

Find

head loss (h_f), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except h_f is given, so isolate h_f 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0016 Pa*s, bed porosity (epsilon) = 0.3100, superficial velocity (V) = 0.0250 m/s, gravity (g) = 9.8200 m/s^2, fluid density (rho) = 870.0 kg/m^3, particle diameter (D_p) = 0.0086 m, bed depth (L) = 2.7500 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=0.4173 mh_{f} = 0.4173\ \text{m}
  6. Step 6 — Check: returning h_f = 0.4173 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=0.4173 mh_{f} = 0.4173\ \text{m}

Why the other options are there

  • 0.8346 — kept a factor of two that cancels in the correct rearrangement.
  • 0.2087 — dropped that same factor in the other direction.
  • 0.4591 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 5
Flow through a packed bed (Ergun-type head loss) — solve for superficial velocity (case 2) — Flow Through a Packed Bed (5)

flow through a packed bed reactor with spherical particles Given dynamic viscosity (mu) = 0.0015 Pa*s; bed porosity (epsilon) = 0.5300; gravity (g) = 9.8400 m/s^2; fluid density (rho) = 1,070 kg/m^3; particle diameter (D_p) = 0.0090 m; bed depth (L) = 1.2500 m; head loss (h_f) = 2.1130 m, determine the superficial velocity (V) in m/s.

Given

  • dynamicviscosity(mu)=0.0015Pa∗sdynamic viscosity (mu) = 0.0015 Pa*s
  • bedporosity(epsilon)=0.5300bed porosity (epsilon) = 0.5300
  • gravity(g)=9.8400m/s2gravity (g) = 9.8400 m/s^2
  • fluiddensity(rho)=1,070kg/m3fluid density (rho) = 1,070 kg/m^3
  • particlediameter(Dp)=0.0090mparticle diameter (D_p) = 0.0090 m
  • beddepth(L)=1.2500mbed depth (L) = 1.2500 m
  • headloss(hf)=2.1130mhead loss (h_f) = 2.1130 m

Find

superficial velocity (V), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except V is given, so isolate V 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that V stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0015 Pa*s, bed porosity (epsilon) = 0.5300, gravity (g) = 9.8400 m/s^2, fluid density (rho) = 1,070 kg/m^3, particle diameter (D_p) = 0.0090 m, bed depth (L) = 1.2500 m, head loss (h_f) = 2.1130 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    V=4.3182 m/sV = 4.3182\ \text{m/s}
  6. Step 6 — Check: returning V = 4.3182 m/s to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
V=4.3182 m/sV = 4.3182\ \text{m/s}

Why the other options are there

  • 8.6364 — kept a factor of two that cancels in the correct rearrangement.
  • 2.1591 — dropped that same factor in the other direction.
  • 4.7500 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 6
Flow through a packed bed (Ergun-type head loss) — solve for bed depth (case 2) — Flow Through a Packed Bed (6)

flow through a packed bed used in a water treatment column Given dynamic viscosity (mu) = 0.0019 Pa*s; bed porosity (epsilon) = 0.4500; superficial velocity (V) = 0.0010 m/s; gravity (g) = 9.8700 m/s^2; fluid density (rho) = 870.0 kg/m^3; particle diameter (D_p) = 0.0022 m; head loss (h_f) = 1.0040 m, determine the bed depth (L) in m.

Given

  • dynamicviscosity(mu)=0.0019Pa∗sdynamic viscosity (mu) = 0.0019 Pa*s
  • bedporosity(epsilon)=0.4500bed porosity (epsilon) = 0.4500
  • superficialvelocity(V)=0.0010m/ssuperficial velocity (V) = 0.0010 m/s
  • gravity(g)=9.8700m/s2gravity (g) = 9.8700 m/s^2
  • fluiddensity(rho)=870.0kg/m3fluid density (rho) = 870.0 kg/m^3
  • particlediameter(Dp)=0.0022mparticle diameter (D_p) = 0.0022 m
  • headloss(hf)=1.0040mhead loss (h_f) = 1.0040 m

Find

bed depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except L is given, so isolate L 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0019 Pa*s, bed porosity (epsilon) = 0.4500, superficial velocity (V) = 0.0010 m/s, gravity (g) = 9.8700 m/s^2, fluid density (rho) = 870.0 kg/m^3, particle diameter (D_p) = 0.0022 m, head loss (h_f) = 1.0040 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=44.1045 mL = 44.1045\ \text{m}
  6. Step 6 — Check: returning L = 44.1045 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=44.1045 mL = 44.1045\ \text{m}

Why the other options are there

  • 88.2090 — kept a factor of two that cancels in the correct rearrangement.
  • 22.0522 — dropped that same factor in the other direction.
  • 48.5149 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 7
Flow through a packed bed (Ergun-type head loss) — solve for head loss (case 3) — Flow Through a Packed Bed (7)

flow through a packed bed of granular filter media Given dynamic viscosity (mu) = 0.0007 Pa*s; bed porosity (epsilon) = 0.5600; superficial velocity (V) = 0.0090 m/s; gravity (g) = 9.7500 m/s^2; fluid density (rho) = 1,110 kg/m^3; particle diameter (D_p) = 0.0092 m; bed depth (L) = 1.5000 m, determine the head loss (h_f) in m.

Given

  • dynamicviscosity(mu)=0.0007Pa∗sdynamic viscosity (mu) = 0.0007 Pa*s
  • bedporosity(epsilon)=0.5600bed porosity (epsilon) = 0.5600
  • superficialvelocity(V)=0.0090m/ssuperficial velocity (V) = 0.0090 m/s
  • gravity(g)=9.7500m/s2gravity (g) = 9.7500 m/s^2
  • fluiddensity(rho)=1,110kg/m3fluid density (rho) = 1,110 kg/m^3
  • particlediameter(Dp)=0.0092mparticle diameter (D_p) = 0.0092 m
  • beddepth(L)=1.5000mbed depth (L) = 1.5000 m

Find

head loss (h_f), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except h_f is given, so isolate h_f 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0007 Pa*s, bed porosity (epsilon) = 0.5600, superficial velocity (V) = 0.0090 m/s, gravity (g) = 9.7500 m/s^2, fluid density (rho) = 1,110 kg/m^3, particle diameter (D_p) = 0.0092 m, bed depth (L) = 1.5000 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=0.0017 mh_{f} = 0.0017\ \text{m}
  6. Step 6 — Check: returning h_f = 0.0017 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=0.0017 mh_{f} = 0.0017\ \text{m}

Why the other options are there

  • 0.0034 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0009 — dropped that same factor in the other direction.
  • 0.0019 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 8
Flow through a packed bed (Ergun-type head loss) — solve for superficial velocity (case 3) — Flow Through a Packed Bed (8)

flow through a packed bed reactor with spherical particles Given dynamic viscosity (mu) = 0.0014 Pa*s; bed porosity (epsilon) = 0.5400; gravity (g) = 9.8300 m/s^2; fluid density (rho) = 860.0 kg/m^3; particle diameter (D_p) = 0.0066 m; bed depth (L) = 1.4500 m; head loss (h_f) = 4.5030 m, determine the superficial velocity (V) in m/s.

Given

  • dynamicviscosity(mu)=0.0014Pa∗sdynamic viscosity (mu) = 0.0014 Pa*s
  • bedporosity(epsilon)=0.5400bed porosity (epsilon) = 0.5400
  • gravity(g)=9.8300m/s2gravity (g) = 9.8300 m/s^2
  • fluiddensity(rho)=860.0kg/m3fluid density (rho) = 860.0 kg/m^3
  • particlediameter(Dp)=0.0066mparticle diameter (D_p) = 0.0066 m
  • beddepth(L)=1.4500mbed depth (L) = 1.4500 m
  • headloss(hf)=4.5030mhead loss (h_f) = 4.5030 m

Find

superficial velocity (V), in m/s

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except V is given, so isolate V 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that V stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0014 Pa*s, bed porosity (epsilon) = 0.5400, gravity (g) = 9.8300 m/s^2, fluid density (rho) = 860.0 kg/m^3, particle diameter (D_p) = 0.0066 m, bed depth (L) = 1.4500 m, head loss (h_f) = 4.5030 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    V=4.0525 m/sV = 4.0525\ \text{m/s}
  6. Step 6 — Check: returning V = 4.0525 m/s to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
V=4.0525 m/sV = 4.0525\ \text{m/s}

Why the other options are there

  • 8.1049 — kept a factor of two that cancels in the correct rearrangement.
  • 2.0262 — dropped that same factor in the other direction.
  • 4.4577 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 9
Flow through a packed bed (Ergun-type head loss) — solve for bed depth (case 3) — Flow Through a Packed Bed (9)

flow through a packed bed used in a water treatment column Given dynamic viscosity (mu) = 0.0016 Pa*s; bed porosity (epsilon) = 0.3200; superficial velocity (V) = 0.0330 m/s; gravity (g) = 9.8900 m/s^2; fluid density (rho) = 1,090 kg/m^3; particle diameter (D_p) = 0.0050 m; head loss (h_f) = 1.0040 m, determine the bed depth (L) in m.

Given

  • dynamicviscosity(mu)=0.0016Pa∗sdynamic viscosity (mu) = 0.0016 Pa*s
  • bedporosity(epsilon)=0.3200bed porosity (epsilon) = 0.3200
  • superficialvelocity(V)=0.0330m/ssuperficial velocity (V) = 0.0330 m/s
  • gravity(g)=9.8900m/s2gravity (g) = 9.8900 m/s^2
  • fluiddensity(rho)=1,090kg/m3fluid density (rho) = 1,090 kg/m^3
  • particlediameter(Dp)=0.0050mparticle diameter (D_p) = 0.0050 m
  • headloss(hf)=1.0040mhead loss (h_f) = 1.0040 m

Find

bed depth (L), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except L is given, so isolate L 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that L stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0016 Pa*s, bed porosity (epsilon) = 0.3200, superficial velocity (V) = 0.0330 m/s, gravity (g) = 9.8900 m/s^2, fluid density (rho) = 1,090 kg/m^3, particle diameter (D_p) = 0.0050 m, head loss (h_f) = 1.0040 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    L=2.4210 mL = 2.4210\ \text{m}
  6. Step 6 — Check: returning L = 2.4210 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
L=2.4210 mL = 2.4210\ \text{m}

Why the other options are there

  • 4.8421 — kept a factor of two that cancels in the correct rearrangement.
  • 1.2105 — dropped that same factor in the other direction.
  • 2.6632 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

Example 10
Flow through a packed bed (Ergun-type head loss) — solve for head loss (case 4) — Flow Through a Packed Bed (10)

flow through a packed bed of granular filter media Given dynamic viscosity (mu) = 0.0008 Pa*s; bed porosity (epsilon) = 0.4100; superficial velocity (V) = 0.0090 m/s; gravity (g) = 9.7300 m/s^2; fluid density (rho) = 870.0 kg/m^3; particle diameter (D_p) = 0.0082 m; bed depth (L) = 2.7500 m, determine the head loss (h_f) in m.

Given

  • dynamicviscosity(mu)=0.0008Pa∗sdynamic viscosity (mu) = 0.0008 Pa*s
  • bedporosity(epsilon)=0.4100bed porosity (epsilon) = 0.4100
  • superficialvelocity(V)=0.0090m/ssuperficial velocity (V) = 0.0090 m/s
  • gravity(g)=9.7300m/s2gravity (g) = 9.7300 m/s^2
  • fluiddensity(rho)=870.0kg/m3fluid density (rho) = 870.0 kg/m^3
  • particlediameter(Dp)=0.0082mparticle diameter (D_p) = 0.0082 m
  • beddepth(L)=2.7500mbed depth (L) = 2.7500 m

Find

head loss (h_f), in m

Start with the thinking

  • The governing relation printed in this handbook section is Flow through a packed bed (Ergun-type head loss).
  • Everything except h_f is given, so isolate h_f 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.
  • Flow through a packed bed filter or reactor obeys a Darcy/Ergun-type head loss relation with the bed porosity.

Step-by-step solution

  1. Step 1 — State the governing relation:

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}
  2. Step 2 — Rearrange the relation so that h_f stands alone on the left-hand side.

  3. Step 3 — List the givens: dynamic viscosity (mu) = 0.0008 Pa*s, bed porosity (epsilon) = 0.4100, superficial velocity (V) = 0.0090 m/s, gravity (g) = 9.7300 m/s^2, fluid density (rho) = 870.0 kg/m^3, particle diameter (D_p) = 0.0082 m, bed depth (L) = 2.7500 m.

  4. Step 4 — Substitute the given values into the rearranged relation.

  5. Step 5 — Evaluate:

    hf=0.0264 mh_{f} = 0.0264\ \text{m}
  6. Step 6 — Check: returning h_f = 0.0264 m to

    hfL=150μ(1−ϵ)2Vϵ3gρDp2\dfrac{h_f}{L} = \dfrac{150 \mu (1-\epsilon)^2 V}{\epsilon^3 g \rho D_p^2}

    reproduces the given quantities, and both sides carry the same units.

Answer:
hf=0.0264 mh_{f} = 0.0264\ \text{m}

Why the other options are there

  • 0.0527 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0132 — dropped that same factor in the other direction.
  • 0.0290 — rounded an intermediate value before the final step.

Reference: FE Handbook — Flow Through a Packed Bed

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