Calculation Results
Total Dynamic Head
TDH (subtotal)--
TDH (psi)--
Recommended Head--
Rec. Head (psi)--
Pump Power--
Specific Gravity--
| Component | Head Loss (ft) | Head Loss (psi) | % of Total |
|---|
Method Notes
- Friction: Darcy-Weisbach h_f = f * (L/D) * (V^2/2g)
- Friction factor: Swamee-Jain explicit approximation of Colebrook-White (Re > 5000)
- Fitting losses: K-factor method, h_f = K * (V^2/2g), values from Crane TP-410 and ASHRAE
- Pump power: HP = (GPM * Head_ft * SG) / (3960 * efficiency)
- Calculations assume turbulent flow. Verify Re > 4000 for all pipe sections.
- For laminar/transitional flow, consult manufacturer curves or iterative Colebrook-White.
NPSHA Analysis
NPSHA--
NPSHR--
Margin (NPSHA - NPSHR)--
Cavitation Risk--
| Term | Value | Description |
|---|
Method Notes
- NPSHA = H_atm + H_static_suction - H_friction_suction - H_vapor
- All terms in feet of head. H_atm = atmospheric pressure head at site elevation.
- H_vapor from water vapor pressure table at fluid temperature (Engineering ToolBox / NIST).
- Cavitation risk: OK (margin > 3 ft), CAUTION (1-3 ft), DANGER (< 1 ft or negative).
- For pressurized tanks, add tank gauge pressure to atmospheric pressure.
Affinity Law Results
New Flow (Q2)--
New Head (H2)--
New Power (P2)--
Flow Ratio--
Head Ratio--
Power Ratio--
Affinity Laws
- Speed change: Q2/Q1 = N2/N1, H2/H1 = (N2/N1)^2, P2/P1 = (N2/N1)^3
- Impeller trim: Q2/Q1 = D2/D1, H2/H1 = (D2/D1)^2, P2/P1 = (D2/D1)^3
- Affinity laws apply to the same pump at similar operating points.
- For large speed changes (>50%), verify with manufacturer performance curves.
- Impeller trim limited by pump casing design — consult manufacturer minimum diameter.