Pump Horsepower (SI Units) Calculator

Pump Horsepower Formula:

\[ HP = \frac{Q \times H \times \rho \times g}{3960 \times 0.7457 \times \eta} \]

Flow Rate (Q):

m³/s

Head (H):

meters

Density (ρ):

kg/m³

Efficiency (η):

(0-1)

Pump Horsepower (HP):

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1. What is Pump Horsepower?

Pump horsepower (HP) is the power required to move a fluid at a specified flow rate against a specified head. This calculation converts the SI unit power calculation to traditional horsepower units, accounting for pump efficiency.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

\[ HP = \frac{Q \times H \times \rho \times g}{3960 \times 0.7457 \times \eta} \]

Where:

\( Q \) — Volumetric flow rate (m³/s)
\( H \) — Total dynamic head (meters)
\( \rho \) — Fluid density (kg/m³)
\( g \) — Acceleration due to gravity (9.81 m/s²)
\( \eta \) — Pump efficiency (0-1)
3960 — Conversion factor (ft-lb/min per HP)
0.7457 — kW to HP conversion factor

Explanation: The formula calculates the hydraulic power and converts it to horsepower, adjusting for pump efficiency.

3. Importance of Pump HP Calculation

Details: Accurate horsepower calculation is essential for proper pump selection, motor sizing, and energy efficiency considerations in fluid systems.

4. Using the Calculator

Tips: Enter flow rate in m³/s, head in meters, density in kg/m³ (1000 for water), and efficiency as a decimal (e.g., 0.85 for 85%). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between hydraulic HP and brake HP?
A: Hydraulic HP is the theoretical power needed to move the fluid, while brake HP includes pump inefficiencies (what the motor must actually deliver).

Q2: Why is density important in the calculation?
A: Denser fluids require more power to pump at the same flow rate and head. Water at 1000 kg/m³ is the standard reference.

Q3: What are typical pump efficiencies?
A: Centrifugal pumps typically range from 40-85% efficiency depending on size and design. Positive displacement pumps can reach 90%.

Q4: How does viscosity affect the calculation?
A: High viscosity fluids may require more power than calculated here, as this formula assumes Newtonian fluid behavior.

Q5: Can this be used for air or gas pumps?
A: For compressible fluids, additional factors like compression ratio and specific heat ratio must be considered.