Maximum Flow Calculator

• Area–Velocity: Q = A \times v where Q is volumetric flow, A area, and v average velocity.
• Orifice discharge: Q = C\_d \times A \times \sqrt{2\Delta P/\rho}. With head input, \Delta P = \rho g h.
• Pipe (friction-limited): Darcy–Weisbach: \Delta P = f \,(L/D)\,(\rho v^2/2). The friction factor f is estimated from Reynolds number using a smooth approximation, iterated to consistency.

1. Select a Model matching your setup (pipe, orifice, or area–velocity).
2. Enter fluid Density. For pipe flow, also enter Viscosity.
3. Fill the model-specific fields (geometry, pressure drop, length, diameter).
4. Pick your preferred Output flow unit.
5. Click Calculate Maximum Flow. Results appear above the form.
6. Use Download CSV or Download PDF for reports.

1) What “maximum flow” means

Maximum flow is the highest sustainable volumetric rate under defined limits. Limits often come from available pressure, allowable velocity, pipe sizing, or a restrictive component. The tool reports volumetric and mass flow so you can compare capacity across scenarios.

2) Continuity and the area–velocity method

When you already know an average cross-section velocity, continuity gives a direct estimate: Q = A × v. It is useful for ducts, channels, and quick “capacity” checks. Because velocity can vary across the section, using a well-justified mean velocity improves the accuracy of this approach.

3) Orifice discharge from pressure drop

An orifice converts pressure energy into kinetic energy. The relation Q = C_d A √(2ΔP/ρ) includes a discharge coefficient that captures contraction and losses. If you have a liquid head instead, the calculator converts it using ΔP = ρ g h.

4) Pipe flow limited by friction

For long pipes, friction dominates. Darcy–Weisbach relates the available pressure drop to velocity: ΔP = f (L/D) (ρ v²/2). Because the friction factor depends on Reynolds number and roughness, the calculator iterates to a consistent solution for v and Q.

5) Reynolds number and flow regime

Reynolds number Re = ρ v D / μ indicates whether the flow is laminar or turbulent. Laminar flow increases resistance sharply at low Re, while turbulent flow depends more on roughness. Reporting Re with the results helps you judge whether assumptions and coefficients are appropriate for your fluid conditions.

6) Roughness, fittings, and safety factors

Pipe roughness raises friction losses and can significantly reduce capacity at high Re. Real systems also include bends, valves, entrances, and expansions that add “minor losses.” If you know an equivalent length or extra losses, include them by increasing L or ΔP.

7) Units, density, and reporting outputs

Accurate unit handling is essential when comparing cases. This calculator standardizes inputs internally, then presents flow in common engineering units such as L/min, m³/h, or gpm. Density influences both the orifice equation and mass flow rate ṁ = ρQ, which is critical for pumps, dosing, and thermal calculations. Temperature shifts can change viscosity and density noticeably.

8) Interpreting results for design decisions

Choose the model matching your constraint: area–velocity, orifice discharge, or pipe friction. If predicted velocity is high, check noise, erosion, and cavitation risk. Export results to document inputs and assumptions, then refine with field data.

1) Which model should I choose?

Choose pipe flow when pressure drop, length, diameter, roughness, and viscosity are known. Use orifice flow for a restriction with a discharge coefficient and ΔP or head. Use area–velocity when you already have a representative mean velocity.

2) What does the discharge coefficient represent?

The discharge coefficient adjusts the ideal orifice equation to account for jet contraction and energy losses. It depends on geometry and Reynolds number. If you do not have test data, use a typical value for your orifice type and refine later.

3) Why is viscosity required for pipe calculations?

Viscosity sets Reynolds number, which determines laminar or turbulent behavior and influences friction factor. Without viscosity, the model cannot reliably connect ΔP to velocity. If you only need a rough estimate, use a representative viscosity for the operating temperature.

4) Does this include minor losses from fittings?

Not explicitly. You can approximate them by increasing the effective length or by increasing the required ΔP to reflect additional losses. For detailed design, calculate minor losses separately and combine them with the major (pipe friction) loss budget.

5) How do I interpret a very high predicted velocity?

High velocity can indicate unrealistic assumptions or an undersized pipe. It may create vibration, noise, erosion, and cavitation issues. Recheck ΔP availability, diameter, and roughness, and compare against recommended velocity limits for your fluid and materials.

6) Are the example rows exact results?

No. The example table is illustrative to show how to enter data and what scale of results to expect. Actual flow depends strongly on your geometry, roughness, fluid properties, and how much pressure drop is truly available in the system.

7) What should I export for documentation?

Export CSV for quick reuse in spreadsheets and batch comparisons. Export PDF for sharing a fixed report that includes inputs and results. Keep a note of the selected model, assumed coefficients, and operating conditions alongside the exported file.