Example data table
| Nozzle | Cd | ΔP | Density | Estimated total flow |
|---|---|---|---|---|
| Circular 8 mm (1 nozzle) | 0.98 | 4 bar | 998 kg/m³ | ~ 14.9 L/min |
| Circular 12 mm (2 nozzles) | 0.95 | 3 bar | 998 kg/m³ | ~ 63.0 L/min |
| Rectangular 4×10 mm (1 nozzle) | 0.90 | 2 bar | 998 kg/m³ | ~ 15.2 L/min |
Formula used
The calculator applies an energy-based nozzle/orifice relationship:
A= nozzle area (m²). For a circle:A = π d² / 4.- Effective pressure drop:
ΔP_eff = ΔP − ρ g Δz(optional elevation correction). - Theoretical jet velocity:
V_th = √(2 ΔP_eff / ρ). - Actual velocity:
V = Cd · V_th. - Flow per nozzle:
Q = Cd · A · √(2 ΔP_eff / ρ). - Total flow:
Q_total = Q · N. - Hydraulic power:
P = ΔP_eff · Q_total. - Reynolds (estimate):
Re = ρ V D_h / μ.
Cd captures contraction and losses at the nozzle entry and along the throat.
How to use this calculator
- Select nozzle shape and enter diameter or width/height.
- Choose pressure method: upstream/downstream or direct drop.
- Enter elevation change if discharge point is higher or lower.
- Provide density, viscosity, Cd, and the number of nozzles.
- Pick your output unit and press Calculate.
- Use Download buttons to save CSV or PDF records.
If the effective pressure becomes negative, adjust inputs or direction.
Professional guidance article
Why nozzle flow matters on construction sites
Nozzles appear in temporary water supply lines, dust suppression systems, curing hoses, fire testing, washdown stations, and air or water jetting tasks. Selecting the right nozzle size is not only a productivity issue; it also affects pump loading, hose safety, overspray, and the ability to meet a specified delivery rate at the workface. A well-sized nozzle helps maintain steady pressure, limits excessive velocity, and reduces unplanned downtime caused by inconsistent discharge.
What the calculator is estimating
This calculator uses an orifice-style approach where the pressure drop is converted into jet velocity, then multiplied by nozzle area and an adjustable discharge coefficient. The discharge coefficient (Cd) represents real losses from entry contraction, internal friction, and geometric imperfections. For sharp-edged openings, Cd is commonly lower; for well-machined nozzles, it is typically higher. The optional elevation input adjusts the effective pressure when the discharge point is above or below the supply reference.
Example data and interpretation
Consider a circular nozzle with diameter 8 mm, Cd 0.98, and an effective pressure drop of 4 bar using water at 998 kg/m³. The calculator predicts about 14.9 L/min from one nozzle. If you install three identical nozzles on a manifold, total discharge rises to about 44.7 L/min (before any manifold losses). This is a practical checkpoint: confirm the pump can sustain the combined flow at the required pressure, and verify that upstream pipe sizing and filtration are adequate to avoid clogging and pressure fluctuations.
Field tips for reliable results
Use consistent units and confirm whether pressures are gauge or absolute in your workflow; the difference cancels when you use a pressure drop, but it can matter if you mix references. Prefer measured pressure at the nozzle inlet when possible, especially for long hose runs. If the nozzle is used for abrasive water, slurry, or air with entrained dust, Cd may change over time as the edge wears. Treat Reynolds number as a qualitative indicator: very low values suggest laminar behavior and higher uncertainty. For critical applications, compare against manufacturer flow curves and validate with a timed bucket test or a calibrated flow meter.
Documentation and handover
Record the selected nozzle size, Cd assumption, and the measured inlet pressure used for the final setup. Save the CSV or PDF output in your commissioning pack so future crews can reproduce the intent. If the scope changes, rerun the calculator with updated pressure and nozzle count to prevent mismatched pumps and unsafe hose reactions.
FAQs
1) What discharge coefficient should I use?
Use vendor data if available. As a rule, sharp-edged openings may be 0.60–0.65, while smooth nozzles are often 0.95–1.00. When uncertain, start conservative and confirm by measurement.
2) Can I use this for air flow?
It can provide a rough estimate if density is set correctly, but compressibility can be significant for air at higher pressure drops. For accurate air sizing, use compressible flow methods and manufacturer charts.
3) Why is my effective pressure drop negative?
This occurs when downstream pressure is higher than upstream, or when elevation rise is large enough that ρgΔz exceeds ΔP. Recheck flow direction, pressure references, and the elevation sign.
4) Does the calculator include pipe and hose losses?
No. It assumes the entered pressure drop is available across the nozzle. For long lines, estimate friction losses separately and use the remaining pressure drop as the nozzle input.
5) How does nozzle count affect results?
Total flow scales linearly with the number of identical nozzles in this model. In practice, manifolds and supply piping may reduce pressure as more nozzles open, lowering actual discharge.
6) What does Reynolds number tell me here?
Reynolds indicates whether flow is likely turbulent or laminar, based on density, viscosity, velocity, and characteristic diameter. Very low Reynolds values can increase uncertainty in Cd and flow prediction.
7) What is the best way to verify in the field?
Measure pressure near the nozzle and validate flow using a calibrated meter or a timed volume test. Compare measured and predicted values, then adjust Cd to match your nozzle condition and setup.