Pump hydraulic power
A compact explanation of hydraulic power, flow conversion and efficiency for preliminary water-pump sizing.
ENGINEERING PRINCIPLE
Hydraulic power is the rate at which a pump increases fluid potential energy; shaft input rises as efficiency falls.
Pinput = ρgQH/ηVariables and units
- ρ in kg/m³
- g in m/s²
- Q in m³/s
- H in m
- η as a decimal
Worked example
For water at Q = 0.015 m³/s, H = 30 m and η = 0.70, Pinput = 1000 × 9.81 × 0.015 × 30 / 0.70 = 6.31 kW.
Calculation method
- Convert flow to m³/s.
- Use a fluid density at the actual process temperature and pressure.
- Divide hydraulic power by an efficiency appropriate to the planned operating point.
Practical applications
- Water-transfer systems
- Process circulation loops
- Initial motor-capacity estimates
Review boundary and reference
- Pump selection needs a system curve and manufacturer curve.
- NPSH, viscosity, motor efficiency and transient duty must be checked separately.
Formula and displayed units independently checked for the stated conditions. This is not a code-compliance design method.
Source: Hydraulic-power relation derived from conservation of energy; use manufacturer curves for selection.