Choked flow through restrictive venturi calculation
Choked flow through restrictive venturi calculation
(OP)
Unable to find an equation that will let me calculate if the venturi is experiencing choked flow. I have inlet pressure, pressure drop and all the other useful info. but all of the formulas i have found require, FL^2, the recovery coefficient. Which I do not have
any help?
any help?





RE: Choked flow through restrictive venturi calculation
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Ted
RE: Choked flow through restrictive venturi calculation
Ever wonder why people go to the trouble to write FAQ? I write them to get information that people need to know available in a peer-reviewed format.
One thing you can be certain of is that if someone puts BS in an eng-tips.com FAQ (or a post for that matter)someone will call them on it pretty quickly--this is the best peer-reviewed site in the world. I don't know if freestudy.co.uk can say that.
David
RE: Choked flow through restrictive venturi calculation
RE: Choked flow through restrictive venturi calculation
RE: Choked flow through restrictive venturi calculation
I need to go through two restrictive venturi's with an inlet pressure of 135 psi and outlet of 30 psi. SG is 1.2, Vapor pressure 4.2 psia, 1.5 inch pipe and 85 gpm.
venturi's are required and i am not sure if i will need two or three and not sure if i am designing this properly.
My initial estimate is the first venturi has a dP of 70 and the second a dP of 35
thoughts?
RE: Choked flow through restrictive venturi calculation
New pressure drops are 62.33 psi on the first and 43.32 for the second. calculations use a vena contracta pressure of -9.5 psi
RE: Choked flow through restrictive venturi calculation
Ted
RE: Choked flow through restrictive venturi calculation
Water: 25.9%
Nitric Acid: 32.92%
Adipic Acid: 13.6%
Glutaric Acid: 10.92%
Succinic Acid: 3.93%
Va: 0.07%
Cu: 0.66%
And 12% Solid Adipic Acid
RE: Choked flow through restrictive venturi calculation
I believe that venturi's are used where you can not tollerate the permenant drop of an orfice plate. (ie flow meters)
I also believe that they are mostly used on gases.
I could be way off base because of the slurry aspect but would you not be better off with a simple orfice plate?
For that matter I prefer to use a VFD on the pump to slow things down and not waste the energy in a large pressure drop if I can make that work.
This advice is probably worth what you paid for it.
Regards
Stonecold
RE: Choked flow through restrictive venturi calculation
i agree, wouldn't be dealing with this if vfd's were installed
RE: Choked flow through restrictive venturi calculation
In your original post you said Since only gases can experience choked flow, several of us assumed that you were using gas. The reason you can't find an equation for liquid choked flow is that there isn't one.
David
RE: Choked flow through restrictive venturi calculation
The pressure recovery coefficient for ventri is normally low amonge 0.1~0.3 still depending on the configuration of the ventri meter.
Hope this help.
RE: Choked flow through restrictive venturi calculation
Ok that makes sense. I have the minimum flow problem as well with some process pumps. They are a clean service so I use the orfice plate.
Sounds like Zdas has the answer for you on making the calculations.
Regards
StoneCold
RE: Choked flow through restrictive venturi calculation
RE: Choked flow through restrictive venturi calculation
RE: Choked flow through restrictive venturi calculation
unless, and that word should be emphasized, unless the fluid undergoes a phase change or in the case of compressible flows reaches sonic velocity at throat conditions.
the situaton is a bit different in the case of flow nozzles, or venturis with a exit angles greater than 45-60Degs. The latter would give you an abrupt pressure drop once you exited the venturi throat.
in your application is is more common to use really thick restriction plates or machined pipe sections, but not venturis
RE: Choked flow through restrictive venturi calculation
Good luck,
Latexman
RE: Choked flow through restrictive venturi calculation
RE: Choked flow through restrictive venturi calculation
so you'd need four venturi's in series assuming that they are widely separated
if you only used two elements, the flow would increase to 120 gpm's with pipe velocities exceeding 20 ft/s....pretty soon you'd have no pipe, oh well...that's a minor detail