Orifice (diaphragm) calculation
1. Introduction
2. Pressure drop through an orifice
1. Introduction
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 diaphragm.
2. Pressure drop through an orifice
The following correlation is given by Gibson, it is reproduced in many books.
Equation 1 : singularity pressure
drop coefficient for an orifice
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 coefficient K can also be calculated thanks to the following graph :
Graph 1 : K coefficient as a
function of d/D
Source
Gibson et al., Hydraulics and its
applications, 5th edition, Constable London, 1952