Description

p₁ - pressure on the inlet

Absolute pressure in front of the orifice

p₂ - pressure on the outlet

Absolute pressure after the orifice

Δp - pressure drop

Pressure difference between pipe start and pipe end

Δω - pressure loss

That can't be recovered after the orifice

D₁ - diameter of tube

Internal pipe diameter

D₂ - orifice size

Diameter of orifice

e - expansion factor

Coefficient used for compressible flow calculation

C - coefficient of discharge

Coefficient used for orifice plate based on ISO 5167

R_eD - upstream Reynolds number

Reynolds number calculated in front of the orifice

K - resistance coefficient

That you can use in pipeline calculation, as orifice is creating local pressure losses in the pipeline

q₁ - volumetric flow rate

Fluid flow rate in terms of units of volume per unit of time on the inlet conditions

q - standard flow

Flow rate at standard conditions. Used only if the selected fluid is gas.

ṁ - mass flow rate

Fluid flow rate in terms of units of mass per unit of time

V₁ - upstream velocity

Flow velocity in front of the orifice where flow diameter is D₁

T₁ - upstream temperature

Fluid temperature for gas density calculation based on the ideal gas state equation

ρ₁ - upstream density

Fluid density in the front of orifice in terms of mass per unit of volume

R - gas constant

Gas constant in terms of energy per unit of mass and temperature, for gas density calculation using ideal gas state equation

κ - isentropic coefficient

Specific heat ratio

ν - kinematic viscosity

Result of fluid particles colliding to each other and moving at different velocities in terms of area per square unit of time

μ - dynamic viscosity

Result of fluid particles colliding to each other and moving at different velocities in terms of mass per square unit of distance and time

Sizing calculation setup

Select orifice type based on the measuring taps placement

Corner taps

When measuring taps are placed in the orifice corners

Flange taps

When measuring taps are placed in the orifice flanges

D - D/2

When measuring taps are placed in front and after the orifice on given distance

Select value to input. You should enter selected one. The other one will be calculated

p₂

pressure downstream from the orifice

Δp

measured pressure difference in front and after the orifice

Select value to input. You should enter selected one. The other one will be calculated

ν

kinematic viscosity

μ

dynamic viscosity

Select value to input. Available only if gas is selected. You should enter selected one. The other one will be calculated

T₁

upstream temperature.

ρ₁

upstream density.

Select fluid type

Gas

for compressible flow where ideal gas state equation is applicable

Liquid

for incompressible flow of liquids

Application of ISO 5167 constraints

ISO constraints

Deselect if you don't want to check if the orifice and the flow conditions are within the limits of the ISO standard.

Why should you use this calculator?

Use this calculator to quickly calculate the actual flow rate through the orifice plate flow meter with only a few inputs. This calculator performs the flow rate calculation from the measured pressure drop caused by the orifice plate inserted in the pipeline.

When is this calculator relevant?

The calculator is suitable for liquids and perfect gases, a subsonic flow of single phase fluid. It is not applicable for pulsating flow. The pipeline should be circular. The calculator is not applicable for rectangular ducts.

When is this calculator not relevant?

This calculator is not suitable for multiphase fluids, like a flow of liquids that contain solid particles or flow of liquids that contain undissolved gases. Also, it is not suitable for gases that are not ideal, i.e., gases that don't relate to the ideal gas law.

What has to be understood to perform the calculation?

To calculate flow rate, you have to enter the orifice plate throat diameter as well as pipe interior diameter, together with fluid properties - density and viscosity. For a gas as flowing fluid, instead of the density, you can enter gas constant, pressure and temperature at actual conditions. Density is then calculated using a perfect gas state equation. You should enter density on real flow conditions - pressure and temperature.

How is the calculation performed?

The calculator is doing calculation according to ISO 5167-2. You can expect to have correct and reliable results only if the orifice plate meets the conditions from the standard.

What are the standard ISO 5137-2 conditions?

For the flow of a perfect gas, the pressure loss created by the orifice must be higher than 0.75.

Orifice meters which have corner pressure tappings or D and D/2 pressure tappings must meet following conditions:

d > 12.5 mm
50 mm < D < 1000 mm
0.1 < β < 0.75
ReD > 5000 for 0.1 < β < 0.56
ReD > 16000xβ² for β > 0.56

Orifice meters which have flange pressure tappings must meet following conditions:

d > 12.5 mm
50 mm < D < 1000 mm
0.1 < β < 0.75
ReD > 5000 and ReD > 170xβ²xD

What happens if a calculation is not within these limits?

If the orifice plate properties or flow conditions are not according to the ISO 5167-2 calculator displays the message. If you want to do calculation regardless of the limitations in the standard, you can choose not to use ISO constraints in the calculation.