Inputs
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Water at ~20°C ≈ 998.2 kg/m³ or 62.3 lb/ft³.
Adjust if necessary; used for head and pressure.
If enabled, velocity uses this Q with global diameter.
Assumes circular pipe. Velocity V = 4Q / (π D²).
Used to estimate equivalent length Le = K·D/f.
If different segments have different diameters, disable global flow/diameter and enter per-row Q or D to compute local velocity.
| # | Component | K | Count | Dia (m) | Flow Q (m³/s) | Velocity V (m/s) | hm per item (m) | hm total (m) | Le per item (m) | Notes |
|---|
Results
- ΣK: 0.000
- Total head loss hm: 0.000 (m)
- Pressure drop ΔP: 0.00 (Pa)
- Equivalent length ΣLe: 0.000 (m)
Velocity uses global or per-row Q and D. ΔP = ρ g hm.
Keyboard & Tips
Press Enter to recompute. Use Tab to navigate. Toggle units anytime.
Example K‑Values (typical references)
| Component | Typical K | Notes |
|---|---|---|
| Entrance, sharp-edged | 0.5 | Depends on geometry and approach. |
| Exit, discharge to reservoir | 1.0 | Often taken as unity. |
| Elbow, 90° standard radius | 0.9 | Radius and roughness affect values. |
| Gate valve, fully open | 0.15 | Much higher when partially closed. |
| Globe valve, fully open | 10.0 | High local loss due to tortuous path. |
| Tee, through run | 0.6 | Branching increases K considerably. |
| Sudden contraction | 0.5 | Varies with area ratio and edge. |
| Sudden expansion | 1.0 | Ideal K ≈ (1 − A₁/A₂)²; 1.0 commonly used. |
Always confirm K from vendor data or standard references for your case.
Formulas Used
- Velocity for circular pipe: V = 4Q / (π D²).
- Minor head loss for one item: hm,i = Ki · Vi² / (2g).
- Total head loss: hm = Σ (counti · hm,i).
- Pressure drop: ΔP = ρ g hm.
- Equivalent length per item: Le,i = Ki · D / f (approximate; requires Darcy f).
Use local velocity V for each component; if diameters change per segment, compute V from that segment’s Q and D.
How to Use
- Select units and set fluid density and gravity if needed.
- Keep “Use global flow and diameter” enabled for constant pipe sizes and Q.
- Otherwise, disable it and enter per-row Q or D for local velocity.
- Enter each component’s name, K, and count. Add notes if useful.
- Optional: set friction factor to estimate equivalent lengths.
- Review results for ΣK, total head loss, pressure drop, and ΣLe.
- Export a CSV of rows or a PDF snapshot for records.
FAQs
Minor losses are additional energy losses caused by fittings, valves, entrances, exits, expansions, and contractions. Each is represented by a dimensionless coefficient K multiplying the local velocity head V²/(2g).
Use global velocity when diameter and flow are uniform. If diameter or flow changes between items, compute velocity locally for that segment to avoid significant error.
They come from experiments, vendor literature, and handbooks. Always verify K for your specific fitting size, radius, roughness, and Reynolds number, as values can vary considerably.
It is an approximation that converts each K into an equivalent straight-pipe length using a friction factor. Accuracy depends on choosing an appropriate Darcy friction factor for the pipe regime.
For low Mach numbers and modest pressure changes, this approach is commonly used. For high compressibility or choked conditions, specialized gas models are recommended.
Estimate f with Moody charts, the Colebrook-White correlation, or manufacturer data. For smooth turbulent flow, values around 0.015–0.025 are common; verify for your Reynolds number and roughness.
If ΔP and velocity are known, you can infer an effective ΣK from K = 2g h / V² where h = ΔP/(ρ g). Compare against tabulated K to sanity‑check your model.