Choked Flow vs. Critical Flow
Choked Flow vs. Critical Flow
(OP)
Can anyone explain the difference between choked flow and critical flow, if there is one?
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Choked Flow vs. Critical Flow
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RE: Choked Flow vs. Critical Flow
We discuss critical pressure and critical temperature related to fluid phase limits. We also discuss critical speeds for large machinery. Please advise the context for critical flow.
RE: Choked Flow vs. Critical Flow
Correct?
RE: Choked Flow vs. Critical Flow
"...Although in actual service, pressure drop ratios can, and often will, exceed the indicated critical values, this is the point where critical flow conditions develop. Thus, for a constant P1, decreasing P2 (i.e., increasing P) will not result in an increase in the flow rate through the valve. Values of x, therefore, greater than the product of either FkxT or FkxTP must never be substituted in the expression for Y. This means that Y can never be less than 0.667. This same limit on values of x also applies to the flow equations that are introduced in the next section. ..."
RE: Choked Flow vs. Critical Flow
RE: Choked Flow vs. Critical Flow
RE: Choked Flow vs. Critical Flow
rmw
RE: Choked Flow vs. Critical Flow
Put simply, choked flow is that flow at which you cannot increase the flow by increasing dP. Flow below choked is called SUB-CRITICAL, flow above choked is called CRITICAL.
Hope this helps,
Ron
Ron Frend
http://www.predicon.net
RE: Choked Flow vs. Critical Flow
Critical refers to the fluid pressures (usually ratio) at the point at which the device becomes "choked"...For gases, the consequence of critical pressure difference is that a reduction in downstream pressure does not increase the flow. The term critical velocity is also used, and its deviation from the stagnant speed of sound gives some indication of the localized departure from predicted velocity due to the geometry of the device that is choked.
RE: Choked Flow vs. Critical Flow
P(crit)=P(upstream)*(2/(k+1))^((k/(k-1))
[both pressures in absolute terms]
This equation usually gives you a P(crit) greater than 1/2 P(upstream), so the 0.5 number is conservative and close enough for most applications (and it is easier to remember than 0.54 for a typical natural gas or 0.53 for air, but other gases can be much higher).
David