Why do you need to calculate power based on pressure and flow?
In the design and energy efficiency evaluation of fluid machinery such as pumps, fans and hydraulic systems, the rapid estimation of input power is very important. This calculation does not depend on the nameplate or measured data of the motor, but is based on the basic physical principle of fluid work.
Core calculation formula
under ideal working conditions (ignoring efficiency loss), the shaft power required by the fluid system (unit: Watt) can be estimated by the following formula:
- power P = Δp×q(International System of Units)
- where:Δpfor pressure difference (Pa, N/m²),Qvolume flow (m³/s)
if you use a common unit of the project: P (kW) ≈ Δp (bar) × Q (L/min) ÷ 600 — this is an approximate conversion (assume 1 bar = 10… Pa, 1 L/min = 1.667 × 10.. m³/s).
Efficiency should be considered in Practical application
due to mechanical, volume and hydraulic losses, the actual driving power shall be:
Pactual= (Δp × Q) / η, where N is system gross efficiency (usually 0.5-0.85, depending on equipment type and working condition).
Pump
Q (m³/s)
Δp = p₂ − p₁
Output stream
precautions
- the formula is applicable to steady-state and incompressible fluids (such as water and oil); The influence of compressibility and temperature change should be considered for gases.
- Pressure units must be unified (recommended for full use Pa and m³/s)
- this method provides a theoretical lower limit, and the safety margin must be superimposed during selection (usually +10% ~ 20%)
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