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flow through orifice

flow through orifice

flow through orifice

(OP)
Can someone tell me, the gas flow volume through an orifice, calculated from the common formula given by different vendors, is at upstream pressure or downstream pressure?  

RE: flow through orifice

either one can be used, but you have to use the correct multiplier in the orifice equation.

RE: flow through orifice

(OP)
I came up with the 667 scfm the following formula. I believe this volume is at set pressure of 275 and not at downstream pressure (atmospheric). The constants and factors I used from Anderson Greenwood catalog. Am I right in my assumption that the volume is at set point??

A =    Area of Orifice    0.134    Sqr. Inch
F =    Factor    6.32    
M =    Molicular Weight of N. Gas    17.4    
T =    Temperature, oR, (oF+460)    560    
Z =    Compressibility Factor    0.97    
C =    Gas Constant    344    
K =    Valve Constant    0.878    
k =    Specific Heat Ratio    1.27    
Kb =    Back Press. Correction Factor    0.8    
Ps =    Set Pressure, psig    275    
Po =    Over Pressure of Set Press.    0.1    
Pa =    Atmospheric Pressure, psia    14.7    
P2  =    Back Pressure, psig        
P =    Pressure absolute    317.2    
            

A =     V x  MTZ / FCKPKb        
            
V =    Flow Rate, SCFM    667    

RE: flow through orifice

You are likely to get better responses to your question if you post in a more suitable group, e.g. fluid mechanics.

M

--
Dr Michael F Platten

RE: flow through orifice

(OP)
hacksaw and Mikeyp; thanks for your input and I will explore the fluid mechanic forum.

RE: flow through orifice

asghar,

this appears to be a restriction orifice or possibly a relief valve as no d/p is provided, and there are curious mentions of a "valve constant" and a back pressure correction factor.


RE: flow through orifice

on closer study. you are dealing with a relief valve.

case in point, the "pressure absolute" = the set pressure + 10% + 14.7 psia.

just follow the instructions in the AG sizing manual. It is very clear. You will also find excellent engineering support from the factory.

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