www.piclist.com/techref/index.htm?key=calc+cfm+pressure

** Is it possible to calculate, or estimate, CFM through an orifice of a

known size by the pressure, psi, on each side of the orifice? This would be

ambient air at about 75 degrees F and, say, 50% relative humidity. **

__________________

There is an easy way to set an UPPER limit - the maximum flow velocity is

sonic in the "throat". While sonic velocity will vary with temperature and

pressure, this fact will give you a first approximation. Sonic flow occurs

for pressure differentials above about 30 psi AFAIR. Searching for "De Laval

nozzle" will give you leads to rocket nozzle design which is what you are

ending up with (even though it doesn't look much like one :-) ).

RM

Somewhat technical intro (but it's going to be)

I think this probably will allow you to work out what you want to know

msohttp://www.anu.edu.au/~geoff/AFD/De_Laval_Nozzle.pdf

Another

http://astron.berkeley.edu/~jrg/ay202/node100.html

Flow through an orifice - just about spot on (maybe :-) )

(See 'Sonic flow from the end of a pipe')

http://www.optimal-systems.demon.co.uk/appendix-e.htm

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