8 replies to this topic

[muthukmaar]

Process air is available at a pressure of 30kg\cm2,172 deg.C through a 6inch pipe for Process at a flow rate of 4500 Normal metre cube per hour. A 3inch tapping is available for Decoking for Fired heaters from the 6inch pipe. It is proposed to take a 3inch line for service air requirements from the 3 inch line used for decoking, how to find the maximum flow possible from the piipe.

[latexman]

Two physical limits are 4500 Ncmh (input) and mach 1 at the end expansion of the 3" line (output), but it could be frictionally choked too.

[muthukmaar]

Can't understand it,can you please explain a bit in detail

[thorium90]

He is referring to choked flow.

The flow will max out at choked flow.

 

The article below will be useful.

 

https://neutrium.net...ow/choked-flow/

[muthukmaar]

Thank You So Much

[breizh]

Hi,

A few documents to share .

 

http://www.engsoft.c...team_flow_e.htm

 

Good luck

Breizh

Edited by breizh, 02 June 2019 - 12:50 AM.

[Art Montemayor]

Latexman has opened the door to a topic that has often caused much confusion and sad results for many Chemical Engineers in Fluid Mechanics courses in the past.  And it is well and good that he has done so because this is a topic that - in my opinion - has been sadly and badly dealt with in many Fluid Mechanics texts.  To my sad luck, I never received a proper, simple answer to my basic question(s) while in university:  How are the speed of sound and mass flow rate related  and what does sound have to do with the flow of gas?

 

After some years of producing and handling gases I now know the answer.  But I also have found many text book and technical article authors that totally avoid this basic question(s).  It seems that they somehow hate the subject or perhaps don't even know the answer.  Nevertheless, as Latex has indicated: the subject won't go away and is one of prime importance to all Chemical Engineers and not just aeronautical engineers and rocket scientists.

 

Breizh has - as usual - contributed some very interesting and useful information and teaching tools that should be of great help to all young engineers and students.  I am attaching a document that might be of interest to those that feel the need to go further into the phenomena of compressible flow and its sonic conditions.  This paper raises some interesting, common points regarding sonic and supersonic flow.  Like its author, I also highly recommend that all Chemical Engineers should own and use Crane's Technical Paper No. 410.

 

 My Current Understanding of Sonic Velocity Limits.docx   57.97KB   53 downloads

[breizh]

Hi All,

In addition to my previous post :

 

https://www.grc.nasa...ane/shortc.html

 

Hope this is helping you.

Breizh

[latexman]

Art,

 

I read Doug McDaniel's document with great interest.  Thank you for sharing.  Doug has excellent insight in this area.  In these days of Mach 6-ish hypersonic missiles, I'm not sure I'm sold yet on supersonic flow cannot occur in a converging-diverging nozzle, but I plan on re-reading his paper a few more times.  The "turbulent jet" theories make a lot of sense to me.

 

This reminds me when I had a eureka moment or epiphany (about 2000) that a thin plate orifice will not choke.  I got it from a memorandum by Dennis Kirk at http://members.ozema...MO_Y Factor.pdf

 

I remember during college the professors taught and I learned that orifices (all orifices) choke flow with enough pressure drop (~ 0.5 x inlet pressure).  I had to un-learn that for thin plate orifices..

Edited by latexman, 03 June 2019 - 09:27 AM.