- Q is nozzle flow (L/min or gpm).
- K is the nozzle K-factor in matching units.
- P is gauge pressure at the nozzle (bar or psi).
- Total system flow: Q_total = N · Q.
- Design margin: Q_design = Q_total · (1 + SF).
- A = π d² / 4, with d in meters.
- ΔP is pressure drop across the orifice (Pa).
- ρ is water density from temperature (kg/m³).
- Jet velocity: v = Q / A.
- Reynolds number: Re = ρ v d / μ.
- Select a model: K-factor for vendor-rated nozzles, or orifice for geometry-based estimates.
- Choose pressure units, then enter nozzle pressure or supply and losses.
- Fill in the nozzle data, plus number of active nozzles.
- Add a safety factor and discharge duration for storage sizing.
- Press calculate, then export the report as CSV or PDF.
| Scenario | Method | Inputs | Expected output |
|---|---|---|---|
| Compact cabinet | K-factor | K=8.0 L/min/√bar, P=70 bar, N=6, SF=10%, t=10 min | Per nozzle ≈ 67 L/min; design flow ≈ 442 L/min; volume ≈ 4,420 L |
| Turbine enclosure | K-factor | K=1.8 gpm/√psi, P=1200 psi, N=12, SF=15%, t=15 min | Per nozzle ≈ 62 gpm; design flow ≈ 857 gpm; volume ≈ 48,650 gal |
| Orifice estimate | Orifice | d=0.20 mm, Cd=0.62, P=80 bar, N=12, SF=10%, t=10 min, 20°C | Per nozzle ≈ 3.3 L/min; design flow ≈ 43.6 L/min; volume ≈ 436 L |
Pressure and flow scaling
Water mist nozzles are rated at nozzle gauge pressure. This calculator treats pressure as the driving term and applies square‑root scaling, so increasing pressure from 50 bar to 100 bar raises flow by √2, not by two. Keep units consistent when comparing bar, kPa, MPa, and psi. If you only know pump pressure, enable supply minus loss to estimate nozzle value.
K-factor versus orifice approach
The K‑factor method matches how manufacturers publish nozzle performance: Q = K·√P. Use it when you have certified K data for a nozzle and strainer configuration. The orifice method is geometry based: Q = Cd·A·√(2ΔP/ρ). It is useful for early feasibility checks, prototype orifice inserts, and sensitivity studies on diameter, but it should be replaced by vendor curves for final design.
Temperature, density, and viscosity inputs
Water properties change with temperature and influence results in the orifice model. Density shifts by a few percent across normal plant conditions, which slightly changes flow for the same pressure. Viscosity changes more, affecting Reynolds number and the likelihood of turbulent discharge. At about 0°C viscosity is near 1.8 mPa·s, around 20°C it is near 1.0 mPa·s, and at 100°C it can drop below 0.3 mPa·s.
Interpreting totals for system sizing
After computing per‑nozzle flow, the calculator multiplies by active nozzle count in each zone to get total demand. The safety factor increases that demand to create a conservative design flow for pump selection and header sizing. Storage volume is then calculated as design flow times duration, giving liters, cubic meters, and US gallons. For example, 200 L/min for 10 minutes requires about 2,000 L before allowance for reserve.
Quality checks before issuing reports
Use the results panel to review inputs, then download CSV or PDF for traceable records. Sanity‑check the flow regime outputs when using the orifice model; very low Reynolds numbers may indicate an unrealistic diameter or pressure. Confirm that “active nozzles” reflects the design discharge scenario, not the installed quantity. Finally, compare computed flow at a reference pressure against vendor data to validate assumptions.
FAQs
What pressure should I enter for a nozzle?
Enter the gauge pressure available at the nozzle inlet. If you only know pump pressure, use the supply minus loss option and enter estimated piping and fitting losses for the discharge path.
When is the K-factor method the better choice?
Use it when the nozzle vendor provides a K value or flow curve at defined pressures. It aligns with certified nozzle performance and is typically the preferred basis for detailed design and submittals.
What does the discharge coefficient represent in the orifice model?
Cd captures real losses from contraction, friction, and non-ideal jet formation. Values near 0.6 are common for sharp-edged orifices, but your insert geometry and surface finish can shift it significantly.
Why does the calculator include a safety factor?
It creates a conservative design flow to cover uncertainty in losses, manufacturing tolerances, and simultaneous nozzle demand. Many engineers apply a margin so the pump and storage still meet requirements under off‑nominal conditions.
What is included in the CSV and PDF downloads?
Both exports include the chosen method, the entered inputs, and the key calculated results. CSV is convenient for spreadsheets and batch comparisons, while PDF is suited for attaching a fixed report to design records.
Can I use this for liquids other than clean water?
For additives, brackish water, or glycol mixes, density and viscosity can change enough to affect orifice results. Use vendor data for the actual fluid, or adjust properties externally and treat the output as a screening estimate.