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1. Introduction

2. Pressure drop through an orifice

3. Orifice flow and pressure drop
calculation tool

Orifices
are often used in fluid mechanics to limit mechanically the flow. It
is important to be able to size them.

The
restriction orifice mentioned here is a thin perforated plate, also
called orifice plate or diaphragm.

The following correlation is given
by Gibson, it is reproduced in many books.It relates the flow through
the orifice and the pressure drop.

**Equation 1 : singularity pressure
drop coefficient for an orifice**

With :

K = Pressure drop coefficient

D = Pipe diameter (m)

d = orifice diameter (m)

**u**_{m} = fluid velocity, before diaphragm, (m/s)

**ΔHs = Pressure drop in m**

K = Pressure drop coefficient

D = Pipe diameter (m)

d = orifice diameter (m)

The coefficient K can also be calculated thanks to the following graph :

*How to calculate the flow through an orifice plate ?*

You can access to an Excel calculation tool in order to assess the flow and pressure drop through an orifice plate : Excel calculation tool

Gibson et al., Hydraulics and its
applications, 5th edition, Constable London, 1952