Calculator Inputs
Use absolute pressures for gas mode. Use pressure difference for liquid mode. The result appears above this form after submission.
Example Data Table
| Case | Fluid Mode | Flow Input | Pressure Condition | Cd | Estimated Area | Equivalent Diameter |
|---|---|---|---|---|---|---|
| 1 | Liquid | 6 L/min water | ΔP = 50 kPa | 0.62 | 16.113 mm² | 4.529 mm |
| 2 | Liquid | 12 L/min water | ΔP = 120 kPa | 0.62 | 20.802 mm² | 5.146 mm |
| 3 | Gas | 0.020 kg/s air | P1 = 3 bar abs, P2 = 1 bar abs | 0.72 | 39.227 mm² | 7.067 mm |
| 4 | Gas | 0.050 kg/s air | P1 = 6 bar abs, P2 = 2.5 bar abs | 0.72 | 49.033 mm² | 7.901 mm |
These sample rows are illustrative benchmarks for checking form usage and output structure.
Formula Used
1) Liquid leakage area from volumetric flow
Q = Cd × A × √(2ΔP / ρ)
A = Q / [Cd × √(2ΔP / ρ)]
2) Liquid leakage area from mass flow
ṁ = ρQ
A = ṁ / [Cd × √(2ρΔP)]
3) Gas leakage area, choked flow
Critical ratio = (2 / (γ + 1))γ / (γ - 1)
If P2/P1 ≤ critical ratio, flow is choked.
A = ṁ / {CdP1 √[(γ / ZRT) × (2 / (γ + 1))(γ + 1)/(γ - 1)]}
4) Gas leakage area, subcritical flow
A = ṁ / {CdP1 √[(2γ / ((γ - 1)ZRT)) × ((P2/P1)2/γ - (P2/P1)(γ + 1)/γ)]}
5) Equivalent circular diameter
d = √(4A / π)
6) Reynolds estimate
Re = ρv d / μ
Where Q is volumetric flow, ṁ is mass flow, A is leakage area, ρ is density, ΔP is pressure difference, Cd is discharge coefficient, γ is specific heat ratio, Z is compressibility factor, R is specific gas constant, T is absolute temperature, d is equivalent diameter, and μ is dynamic viscosity.
How to Use This Calculator
- Choose Liquid or Gas mode.
- Select whether your measured leak rate is volumetric or mass.
- Enter the appropriate pressure values. Use ΔP for liquids and absolute pressures P1 and P2 for gases.
- Enter density for liquids or gas properties for gases.
- Set a realistic discharge coefficient for the suspected leak geometry.
- Enter viscosity if you want a Reynolds estimate.
- Click Calculate Leakage Area.
- Review the result summary, Plotly graph, and export the current result as CSV or PDF.
Frequently Asked Questions
1) What does leakage area mean?
Leakage area is the effective opening size that would pass the measured flow under the stated pressure conditions. It is often smaller than a visible crack because real flow contracts and loses energy near the opening.
2) Why do I need the discharge coefficient?
The discharge coefficient corrects ideal flow equations for contraction and energy losses. A perfectly ideal opening would use 1.0, but real leaks usually require a lower value based on geometry and flow behavior.
3) Should I use gauge pressure or absolute pressure?
Use differential pressure for liquids. Use absolute upstream and downstream pressures for gas mode. Gas compressibility and choking checks depend on absolute pressure, not gauge pressure alone.
4) What happens when gas flow is choked?
Choked flow means the gas reaches sonic conditions at the restriction. Lowering downstream pressure further does not increase mass flux in the same way, so the calculator switches to the choked-flow relation automatically.
5) Can I use this for cracks or slots?
Yes. The result is an effective leakage area. The calculator also converts that area into an equivalent circular diameter, which helps compare non-circular leaks to a circular reference opening.
6) Why is viscosity included?
Viscosity is used here for a Reynolds estimate. That estimate helps you judge whether inertial behavior dominates or whether viscous effects may be more important than the simple orifice-style model suggests.
7) Does the graph change the actual result?
No. The graph keeps the entered flow target fixed and sweeps one pressure condition. It helps you see how sensitive the required leak area is to changing operating pressure.
8) When should I be cautious using this calculator?
Be cautious with multiphase flow, flashing liquids, very long cracks, highly viscous laminar leaks, strong heat transfer, or poorly known discharge coefficients. Those cases may need a more detailed leak model.