Choose Sizing (solve the bore) or Rating (solve the flow), pick the service, enter the conditions and press Calculate.
Liquid: ṁ = Cd·A·√(2ρΔP)
Gas (subcritical): ṁ = Cd·Y·A·√(2ρ₁ΔP)
Gas (choked): ṁ = Cd·A·√(k·ρ₁·P₁·(2/(k+1))^…)
Engineering tips
- Choked gas: when P₂/P₁ ≤ (2/(k+1))^(k/(k−1)) the flow is sonic at the bore and capped by the upstream condition.
- Cd: 0.61 is a screening value for a thin square-edged plate — confirm from geometry/vendor data.
- Cavitation: a low σ or a high single-plate ΔP/P₁ points to a multi-stage RO.
Recommended values
- Bore ratio β: Keep β = d/D ≥ 0.2; very small bores cause high noise and erosion — consider multi-stage / multi-hole.
- Liquid cavitation: Keep downstream pressure above the fluid vapour pressure, or stage the pressure drop.
- Gas choking: Flow chokes at P2/P1 ≤ the critical ratio (≈ 0.5 for air); extra ΔP then adds no flow.
- Cd: Thin-plate sharp-edge ≈ 0.60–0.62; use the ISO 5167 value for the installed β and Re.
Limitations
- Single-stage: Thin-plate ISO 5167 basis — does not size multi-stage or multi-hole plates.
- Not included: Cavitation intensity, downstream acoustic (dBA) noise, and erosion life are separate checks.
About the standards
- ISO 5167: Measurement of fluid flow by means of pressure differential devices.
- Crane TP-410: Flow of Fluids.