In McCabe and Smith, the Orifice Si

[choack]

In McCabe and Smith, the Orifice Sizing equation for mass flowrate for compressible fluid is only applicable to fluids having pressure ratio above 0.53. (page 232, 7th edition).

Can someone advise what equation to use for 0.53 and below? Thanks.

 

[Latexman]

Benedict [J. Basic Eng., 93, 121-137 (1971)]. Referenced in Perry's Handbook.

Good luck,
Latexman

 

[Latexman]

The reference above is for the expansion factor, Y. I have McCabe and Smith's 3rd Ed. so I could not see what equation you are talking about. I hope I guessed right!

Good luck,
Latexman

 

[hacksaw]

in the 7th ed it is on p.213, and references compressible flow through orifices and venturis

the pressure ratio he uses is discharge ratio, i.e. the exit to inlet pressure ratio.

once the discharge is below 0.53 or so, you have sonic flow at the throat of venturi, as the pressure is reduced the mass flow stays fixed, and the basis for critical flow venturi and flow nozzles used in flow calibration

this is only approximately true for sharp edged orifices

the restriction to pressure ratios above 0.53 is for none critical flow conditions

 

[choack]

I think I got my answer....

Thanks for the reply!!

Christopher Kenneth Choa

 

[choack]

Here is the answer!

Christopher Kenneth Choa