Instrumentation Calculators

# Orifice Plate Flow Rate Calculator

An orifice plate is a device used to measure flow rate in pipes. It consists of a thin plate with a hole in the center, inserted perpendicular to the flow in a pipe. The flow rate is calculated based on the pressure difference across the orifice plate.

This orifice plate flow rate calculator determines the flow rate of a fluid passing through an orifice plate based on differential pressure, pipe diameter, and fluid properties. This method is widely used in various industries for its simplicity and accuracy

Where:

• Q = Flow rate m³/s (typically in cubic meters per second or liters per second)
• C = Discharge coefficient (dimensionless)
• A = Cross-sectional area of the orifice m² (square meters)
• ΔP = Differential pressure Pa (pascals)
• ρ = Density of the fluid kg/m³ (kilograms per cubic meter)
• The discharge coefficient is a dimensionless number that accounts for the losses due to the geometry of the orifice and varies based on the type of orifice plate used.
• This accounts for the vena contracta effect and energy losses. It typically ranges from 0.6 to 0.85 for orifice plates.
• The cross-sectional area of the orifice can be calculated using the orifice diameter (d). For a circular orifice, the area is given by:

Where d is the diameter of the orifice.

• Differential pressure is the pressure drop across the orifice plate, typically measured in pascals (Pa). It drives the fluid flow through the orifice. This is measured between the upstream and downstream sides of the orifice plate.
• The density of the fluid is the mass per unit volume, typically measured in kilograms per cubic meter (kg/m³). It influences the flow rate for a given differential pressure. This depends on the fluid being measured and its temperature.
1. Measure or get the orifice plate’s internal diameter.
2. Use the diameter to compute the cross-sectional area using the circle area formula.
3. Determine the differential pressure across the orifice plate.
4. Determine the density of the fluid. This can be found in standard references or determined methodically.
5. Plug all of the data into the flow rate formula to calculate the flow rate.
6. Multiply the flow rate in cubic meters per second by 3600 to convert it to cubic meters per hour.

Here you can refer the calculator for converting Flowrate to Differential Pressure (DP)

Let us assume that you have the following information:

The diameter of the orifice, d, is equal to 0.05 meters.

The differential pressure, denoted by Δ P, is equal to 5000 pascals.

the density of the fluid, ρ = 800 kg/m3

The discharge coefficient, denoted as C, is set to 0.61.

Calculating the cross-sectional area:

A=π×(0.05/2​)2=0.00196m2

Calculating the Flow Rate:

The flow rate is approximately 0.0042 cubic meters per second.

To convert the flow rate from cubic meters per second (m³/s) to cubic meters per hour (m³/h), you can use the following conversion factor:

1 m3/s = 3600 m3/h

To convert the example flow rate:

Q = 0.0042 m3/s

Multiply by 3600

Q = 0.0042×3600 = 15.12 m3/h

The flow rate is approximately 15.12 cubic meters per hour.

• For high-precision measurements, it could be necessary to calculate the discharge coefficient (C) experimentally.
• Incompressible flow is assumed in this formula. Additional factors apply to gasses and compressible fluids.
• The precision of the pressure difference measurement and the discharge coefficient calculation determine the accuracy of the flow measurement.

Here you can refer more Online Instrumentation Calculators Collections

### Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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