7 replies to this topic

[panoska]

Is there a real difference between the two terms: chocked flow and critical fl flow?

[latexman]

No.  Same, same.

[breizh]

Hi,

Choked flow not chocked flow.

Did you ask Google ?

Breizh 

Attached Files

•  Choked Flow of Gases.pdf   387.02KB   28 downloads

[panoska]

Hi Latexman, thanks for the confirmation! I had the same opinion.
Breizh, always first google and then I check with group here! Thanks for the document and the correction!

[fallah]

Is there a real difference between the two terms: chocked flow and critical fl flow?

 

Hi,

 

They are almost the same, but...

 

"Critical" mostly refers to the fluid (gas) pressure (usually in ratio) or velocity at the point at which the flow passing a throttling device such as nozzle, orifice,...becomes critical or choked.

 

On the other hand, "choked" just refers to the flow at critical condition rather than referring to the relevant pressure or velocity.

[panoska]

Hello Breizh, from your attachment I can understand the following:

 

The velocity and the flowrate are not necessarily chocked at the same pressure ratio. We can have chocked velocity, but not chocked flow. 

This is something I did not know at all. And I had the impression that if we are at choked conditions then the flowrate is maximum and it is not increase anymore. With kind of calculations, can we show that the flowrate is choked?

From the attached article, it does not make clear the difference between critical and choked. Can you please further explain it? It differentiates only the choked velocity and choked flowrate.

 

Hello Fallah,

I am happy you answered me. This question comes are consequence of the pressure regulator graph. Where I see that the flowrate is constant after a pressure increase, which means that it is at choked conditions and it is the maximum flowrate at this pressure.

I got confused with your latest sentence can you please explain it further?

 

Critical and choked both mean that we have constant velocity or constant pressure.

Choked flow means directly maximum flowrate through an orifice. Right?

 

Thanks for your answers.

Edited by panagiotis, 25 June 2024 - 02:09 PM.

[fallah]

 

Hello Fallah,

I am happy you answered me. This question comes are consequence of the pressure regulator graph. Where I see that the flowrate is constant after a pressure increase, which means that it is at choked conditions and it is the maximum flowrate at this pressure.

I got confused with your latest sentence can you please explain it further?

 

Critical and choked both mean that we have constant velocity or constant pressure.

Choked flow means directly maximum flowrate through an orifice. Right?

 

Thanks for your answers.

 

Hi,

 

Suppose we have an orifice with constant pressure at the inlet. With decreasing the outlet pressure, initially, the passing flow will be increased so does the velocity of fluid. To continue decreasing the outlet pressure a point will be reached at which further decreasing the outlet pressure will result in no increase in passing flow.

The pressure of that point is titled "critical pressure" and the corresponding fluid flow and fluid velocity are titled "critical or choked flow" and "critical velocity", respectively.  As you see, beyond the critical pressure (lower outlet pressure) the passing flow will be constant at "choked flow" so does the fluid velocity.

Hope, at the moment it has been clarified for you...

[panoska]

Hi Fallah, it is clear.

Thank you!