Static Pressure Drop Calculator
Calculate the static pressure drop in a pipe or duct using the Darcy-Weisbach equation. Supports both laminar and turbulent flow with the Colebrook-White friction factor.
Sum of all fitting/valve K values (elbows, valves, etc.)
Results will appear here.
Formulas Used
Reynolds Number:
Re = ρ·V·D / μ
Darcy Friction Factor:
Laminar (Re < 2300): f = 64 / Re (Hagen-Poiseuille)
Turbulent (Re ≥ 2300): Colebrook-White equation (iterative):
1/√f = −2 log₁₀( ε/(3.7·D) + 2.51/(Re·√f) )
Dynamic Pressure:
q = ½·ρ·V²
Major Pressure Drop (Darcy-Weisbach):
ΔP_major = f · (L/D) · q
Minor Pressure Drop:
ΔP_minor = K_total · q
Total Pressure Drop:
ΔP_total = ΔP_major + ΔP_minor
Assumptions & References
- Steady, incompressible, fully-developed internal flow assumed.
- Pipe is assumed to be straight and circular in cross-section.
- Laminar flow friction factor uses the exact Hagen-Poiseuille solution (f = 64/Re).
- Turbulent friction factor solved iteratively via the Colebrook-White equation (100 iterations, converges to <10⁻¹² tolerance).
- Transitional flow (2300 ≤ Re < 4000) uses the Colebrook-White equation as an approximation; results should be treated with caution in this regime.
- Minor losses are approximated as ΔP = K·q; K values must be summed externally (e.g., elbow K≈0.9, gate valve K≈0.2).
- Typical roughness values: commercial steel ε = 0.000046 m, drawn tubing ε = 0.0000015 m, cast iron ε = 0.00026 m, smooth pipe ε = 0.
- Typical air properties (20°C, 1 atm): ρ = 1.204 kg/m³, μ = 1.81×10⁻⁵ Pa·s.
- Typical water properties (20°C): ρ = 998 kg/m³, μ = 1.002×10⁻³ Pa·s.
- References: Moody (1944); White, F.M. Fluid Mechanics, 8th ed.; Colebrook & White (1937), Proc. R. Soc. London.