Instrumentation Tools

# Orifice Plate Flow and Pressure Drop Calculation Excel Tool

In fluid mechanics, orifices serve as crucial devices for regulating flow by mechanically restricting it. When fluid passes through an orifice plate, it encounters a pressure decrease, making it essential to accurately size the orifice plate to control the flow effectively.

It’s worth noting that the pressure drop across an orifice can also serve as a method for determining the flow rate of the fluid passing through it.

The type of orifice referred to here is typically a thin, perforated plate known as an orifice plate or diaphragm.

pressure drop coefficient for an orifice=

Where

K = Pressure drop coefficient

D = Pipe diameter (m)

d = orifice diameter (m)

um = fluid velocity, before diaphragm, (m/s)

ΔHs = Pressure drop in m

The following graph also makes it possible to determine the coefficient K:

This more direct relationship is provided by ISO 5167, which is utilized in the Calculator that can be found below.

Where

qm = flow rate of the fluid through the orifice (kg/s)
C = coefficient of discharge, which for an orifice plate is typically 0.65.
β = d/D
ε = Expansibility factor (only for gas; epsilon = 1 for liquid)
D = pipe diameter (m)
d = orifice diameter (m)
ρ = fluid density (kg/m3) upstream of the orifice plate
ΔP = The pressure drop that occurs via the orifice plate is measured in Pa.

With the help of the following formula, one is able to determine the expansibility factor for gasses.

Where:

ε = Expansibility factor (only for gas; epsilon = 1 for liquid)
β = d/D
p1 = upstream pressure (Pa)
p2 = downstream pressure (Pa)

For calculating the flow and pressure drop via an orifice plate, you can use an Excel calculation tool