The amount of permanent pressure loss varies with the beta ratio (d/D). For a square-edged orifice, the permanent pressure loss as a percentage of the orifice differential pressure (delta-p) is:
46% for d/D = 0.75
52% for d/D = 0.70
63% for d/D = 0.60
73% for d/D = 0.50
81% for d/D = 0.40
88% for d/D = 0.30
93% for d/D = 0.20
97% for d/D = 0.10
The equation for this for those who are interested is:
where:
hl = permanent pressure loss
hw = orifice differential pressure (same units as hl, but generally inches of water in US)
B = d/D = beta ratio
There are other equations available that can be applied to just about any flow device, including quadrant- and square-edged orifices, nozzles, venturies, Annubars, pitot tubes, target, turbine, and vortex meters. This and other great flow stuff is in one of the best flow metering books I have run across:
"Flow Metering Engineering Handbook", Richard W. Miller, McGraw-Hill. It is a bit pricey, and used to be available from ISA where I got mine, although it doesn't appear on the web store now. It has saved my day far more than once when I needed detailed technical data on flow metering.
Thank you for the information, it proved very helpful to me.
>The amount of permanent pressure loss varies with the beta
>ratio (d/D). For a square-edged orifice, the permanent
>pressure loss as a percentage of the orifice differential
>pressure (delta-p) is:
>
>46% for d/D = 0.75
>52% for d/D = 0.70
>63% for d/D = 0.60
>73% for d/D = 0.50
>81% for d/D = 0.40
>88% for d/D = 0.30
>93% for d/D = 0.20
>97% for d/D = 0.10
>
>The equation for this for those who are interested is:
>
>hl / hw = 1 - 0.24 * B - 0.52 * B**2 - 0.16 * B**3
>
>where:
> hl = permanent pressure loss
> hw = orifice differential pressure (same units as hl, but generally
> inches of water in US)
> B = d/D = beta ratio