centrifugal pump flow rate calculator

Centrifugal Pump Flow Rate Calculator

To estimate the flow rate of a centrifugal pump, you can use fundamental hydraulic equations or online calculators. Below are the key formulas and steps for manual calculation.

1. Basic Flow Rate Formula

The flow rate (Q) of a centrifugal pump depends on:

• Pump efficiency (η)

• Power input (P)

• Total head (H)

• Liquid density (ρ)

Formula:

$$Q=\frac{P\times \eta \times 3600}{\rho \times g\times H}$$

Where:

• $Q$ = Flow rate (m³/h)

• $P$ = Power input (kW)

• $\eta$ = Pump efficiency (decimal, e.g., 0.8 for 80%)

• $\rho$ = Liquid density (kg/m³, ~1000 for water)

• $g$ = Gravity (9.81 m/s²)

• $H$ = Total head (m)

Example Calculation:

If:

• Power (P) = 10 kW

• Efficiency (η) = 85% (0.85)

• Total head (H) = 50 m

• Density (ρ) = 1000 kg/m³

$$Q=\frac{10\times 0.85\times 3600}{1000\times 9.81\times 50}\approx \ast \ast 6.24{\text{m}}^3\mathrm{/}\text{h}\ast \ast$$

2. Alternative Method (Using Pump Curve)

If you have the pump performance curve, locate:

1. Head (H) vs. Flow (Q) curve.

2. Find the intersection of your system head with the pump curve.

https://www.engineeringtoolbox.com/docs/documents/1030/centrifugal-pump-performance-curve.png
*(Example: At 50m head, flow rate ≈ 6 m³/h.)*

3. Online Calculators & Tools

For quick estimates, use these free tools:

1. Engineering Toolbox Pump Calculator – Link

2. LMNO Engineering Calculator – Link

3. Hydraulic Institute (HI) Tools – Link

4. Key Factors Affecting Flow Rate

• Impeller diameter (larger = higher flow).

• Speed (RPM) – Affinity Laws:

  $$Q_2=Q_1\times \left(\frac{N_2}{N_1}\right)$$

  (Flow is directly proportional to speed.)

• System resistance (higher friction = lower flow).

5. Troubleshooting Low Flow

If actual flow < calculated:
✔ Check for clogged impeller/suction.
✔ Verify correct rotation direction.
✔ Inspect worn seals/impeller.
✔ Ensure discharge valve is fully open.

Need a Custom Calculation?

Provide these details for an accurate estimate:

• Pump power (kW/HP)

• Total head (m/ft)

• Liquid type (water, oil, etc.)

• Pump model (if available)

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