Orifice (diaphragm) calculation
Equivalent length key pipe components
Singularity coefficient key pipe components
Partially filled pipe
Control valve sizing for gases
Pressure safety valves
Velocity in pipes
1. IntroductionOrifices 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 diapgragm.
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
Gibson et al., Hydraulics and its applications, 5th edition, Constable London, 1952