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flow restrictions for compressed air

flow restrictions for compressed air

flow restrictions for compressed air

(OP)
does anyone have the formula for calculating the maximum flow rate for compressed air through a pipe (say 6" dia)?

RE: flow restrictions for compressed air

There is a simple answer to that, if you have choked flow the velocity (in Imperial Units) is:

v=(k*g*R(gas)*T)^0.5

Convert that to a volume flow rate, or a mass flow rate using the usual equations.  You have choked flow (which is the maximum flow rate of a compressible fluid) whenever the downstream pressure is less than:

P(max choked) = P(upstream)*(2/(k+1))^(k/(k-1))

In both equations "k" is the ratio of specific heats and all pressures and temperatures must be in absolute terms.

If you are looking for a "maximum commercial" flow rate, then you'll have to restate your question.  That value is very dependent upon maximum allowable velocity which is a function of pressure and temperature.

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: flow restrictions for compressed air

(OP)
Ok, thanks.

RE: flow restrictions for compressed air

For a perfect gas, constant specific heat, the max flow will occur if choking conditions occur.

For adiabatic flow, the Mach No. =1
For isothermal flow the Mach No.  =  sqrt (1/gamma), where gamma is the ration of the specific heats Cp/Cv

Regards

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