Orifice Flow Calculator Formula
Understand the math behind the orifice flow calculator. Each variable explained with a worked example.
Formulas Used
Volumetric Flow Rate
flow_m3s = cd * a_orifice * sqrt(2 * dp_pa / density)Flow Rate
flow_lps = cd * a_orifice * sqrt(2 * dp_pa / density) * 1000Variables
| Variable | Description | Default |
|---|---|---|
cd | Discharge Coefficient (Cd) | 0.62 |
orifice_dia | Orifice Diameter(mm) | 50 |
delta_p | Differential Pressure(kPa) | 20 |
density | Fluid Density(kg/m^3) | 1000 |
d_m | Derived value= orifice_dia / 1000 | calculated |
a_orifice | Derived value= pi * pow(d_m, 2) / 4 | calculated |
dp_pa | Derived value= delta_p * 1000 | calculated |
How It Works
Orifice Plate Flow Measurement
An orifice plate restricts flow in a pipe, creating a measurable pressure difference proportional to flow rate.
Formula
Q = Cd A sqrt(2 delta_P / rho)
where Cd is the discharge coefficient (typically 0.60-0.65 for sharp-edged orifices), A is the orifice area, delta_P is the measured differential pressure, and rho is fluid density.
Worked Example
A 50 mm orifice in a water pipe with 20 kPa differential pressure, Cd = 0.62.
cd = 0.62orifice_dia = 50delta_p = 20density = 1000
- 01A = pi x 0.05^2 / 4 = 0.001963 m^2
- 02sqrt(2 x 20000 / 1000) = sqrt(40) = 6.325 m/s
- 03Q = 0.62 x 0.001963 x 6.325 = 0.00770 m^3/s = 7.70 L/s
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