Engineering CalculatorsFlow in Pipes / Coolant Pump Sizing
Pressure drop of a liquid flowing through a pipe or hose run (Darcy-Weisbach with the Swamee-Jain friction factor, plus fitting minor losses and static head), and the pump head and power needed to drive it — pairs with the Heatsink and Heat Exchanger calculators to size a whole liquid-cooling loop.
| Component | kPa | % |
|---|---|---|
| Major (pipe friction) | 6.13 | 53 |
| Minor (fittings, ΣK=5) | 5.41 | 47 |
| Static (elevation 0 m) | 0 | 0 |
| Total | 11.54 | 100 |
New to Darcy-Weisbach / Colebrook-White? Read the guide: Pipe Pressure Drop & Pump Sizing: Darcy-Weisbach and the Friction Factor — a plain-language explainer of the standard behind this calculator.
Steady incompressible fully-developed flow of a Newtonian fluid in a single uniform-diameter pipe. Pressure drop is Darcy-Weisbach, ΔP = f·(L/D)·(ρ·v²/2), with the Darcy friction factor from f = 64/Re for laminar flow (Re < 2300) and the Swamee-Jain explicit fit to Colebrook-White, f = 0.25/[log₁₀(ε/(3.7·D) + 5.74/Re^0.9)]², for turbulent flow (Re ≥ 4000); the transitional band (2300–4000) is linearly interpolated, since real transitional flow isn't predictable. Fitting minor losses use ΣK·(ρ·v²/2) with representative textbook / Crane TP-410 K values — these vary materially by source, connection type and size, so use the manufacturer's K where available. Pipe roughness values are the classic Moody figures for new, clean pipe; aged, corroded or scaled pipe is rougher. Static head is ρ·g·Δz. Fluid density reuses this site's coolant presets (a single representative value — for water it doesn't capture the ~4% density change over 0–100 °C) and kinematic viscosity reuses the Heat Exchanger calculator's temperature-interpolated transport table, so the two tools agree on fluid data. Pump duty is H = ΔP/(ρ·g), hydraulic power ΔP·Q, and shaft power ÷ a constant assumed pump efficiency — size the real pump against its published head-vs-flow curve at this operating point.
Validated: reproduces a hand-worked textbook case — water at 20 °C (ρ ≈ 998 kg/m³, ν = 1.004×10⁻⁶ m²/s) flowing at 2.0 m/s through 100 m of 50 mm commercial-steel pipe (ε = 0.046 mm) gives Re ≈ 99,600 (turbulent), Swamee-Jain f = 0.0221 (matching the Moody chart), a major pressure drop of ≈ 88 kPa and a pump head of ≈ 9.0 m — all reproduced exactly. The laminar branch returns f = 64/Re exactly (Re = 100 → f = 0.64), and the minor-loss and static-head terms were checked against hand calculation.