Enter flow, pipe, and orifice sizes to estimate pressure drop accurately fast. Compare units, view head loss, and export results as CSV/PDF whenever needed.
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| Q (m³/h) | D (mm) | d (mm) | ρ (kg/m³) | Cd | Y | ΔP (kPa) |
|---|---|---|---|---|---|---|
| 12 | 100 | 60 | 998 | 0.61 | 1.00 | ≈ 6.0 |
| 8 | 80 | 40 | 900 | 0.61 | 1.00 | ≈ 6.6 |
| 150 | 200 | 120 | 1.20 | 0.61 | 0.98 | ≈ 5.7 |
A sharp-edged orifice plate relates volumetric flow rate Q and differential pressure ΔP by:
This calculator solves for ΔP:
Orifice plates create a controlled restriction so velocity rises and static pressure drops across the plate. Measuring this differential pressure supports flow monitoring in water distribution, chemical processing, and HVAC hydronics. The design is passive and rugged for harsh services.
The diameter ratio β = d/D shapes sensitivity. Small β produces larger pressure drop and stronger signal, while large β reduces signal and increases uncertainty. Many standards prefer mid‑range β values to balance signal and permanent loss. Keep diameters round and concentric.
The discharge coefficient Cd accounts for vena contracta formation, edge sharpness, and Reynolds-number effects. Calibrations often show Cd near 0.60–0.62 for sharp-edged plates, but installations can deviate if edges wear or deposits build. Use certified Cd when available and treat Cd as a key uncertainty term.
For compressible flow, the expansibility factor Y adjusts the ΔP–flow relationship. As pressure falls, density changes and the same volumetric flow may require different ΔP. Typical Y values are slightly below 1 and depend on pressure ratio and gas properties. When ΔP is small versus upstream pressure, Y approaches 1.
Density ρ should match operating temperature and composition. A density error propagates directly into computed ΔP. For liquids, use a property table or measurement near the meter. For gases, use an equation of state or historian values. If density varies, evaluate ΔP at minimum and maximum ρ.
Teams compare results in Pa, kPa, bar, psi, or millimetres of water. Consistent conversions prevent specification mistakes when transmitters are ranged in one unit but reports use another. Export files improve traceability by capturing the exact inputs and outputs for review and auditing.
Equivalent head loss expresses ΔP as metres of fluid column: h = ΔP/(ρg). This helps pump sizing and energy assessment because head integrates with system curves. Higher head improves signal but raises operating cost. Comparing head loss across β values supports balanced design choices.
Verify d < D and keep β within your chosen standard’s recommended range. Upstream disturbances, short straight runs, and poor tap placement can bias readings. Keep impulse lines clear and avoid trapped gas or sediment. For high accuracy, calibrate or validate against a reference method.
For best results, pair the computed ΔP with your transmitter range and allowable permanent pressure loss. Recheck inputs after maintenance, especially plate replacement. Recording β, Cd, and density with each run makes comparisons meaningful across different operating points and fluids, and health indicators over time.
It reports the differential pressure needed to sustain your entered volumetric flow through the orifice. It also shows equivalent head loss and common pressure units for easy instrumentation comparison.
Many standards favor mid‑range β values because very small β creates large losses, and very large β reduces signal. Keep β below 1 and follow your project standard for recommended limits.
Use Y below 1 for gases or vapors where compressibility matters. If ΔP is small relative to upstream pressure, Y approaches 1 and results resemble the incompressible case.
Use a certified value when available. Otherwise, start near 0.61 for a sharp-edged plate and refine with calibration or a standard-based correlation. Edge wear and fouling can change Cd over time.
Not directly. Reynolds effects are commonly absorbed into Cd when you use a correlation or calibrated value. If you expect large Reynolds variation, use Cd appropriate for your operating range.
Convert mass flow to volumetric flow using Q = ṁ/ρ at the operating density, then enter Q. For gases, ensure ρ reflects actual pressure and temperature, not standard conditions.
Head loss expresses ΔP as meters of fluid column, which links naturally to pump curves and system pressure budgets. It helps you judge whether the metering signal is worth the ongoing energy cost.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.