Vena Contracta

[GJZ]

When a gas flows from a plenum into a pipe of diameter D, I understand that the vena contracta forms approximately 0.5D downstream from the pipe entrance. How far downstream from the vena contracta or the pipe entrance does the gas flow become fully distributed across the pipe area?

 

[TD2K]

Per my copy of Miller, flow measurment engineering handbook, it's about 2 pipe diameters.

 

[KernOily]

Hey TD2K, you better guard that copy of Miller's with your life 'cuz it's now out-of-print. But - I'll trade ya mine for your copy of "Petroleum Refiner's Handbook" tho... ;-) Thanks!
Pete
P. J. (Pete) Chandler, PE
Principal Engineer
Mechanical, Piping, Thermal, Hydraulics
Processes Unlimited International, Inc.
Bakersfield, California USA
pjchandl@prou.com

 

[TD2K]

That's too bad, it was the bible from the Instrumentation engineers I've talked to.

 

[GJZ]

Dear TD2K - Thanks for your help, but is that two diameters from the pipe entrance or from the vena contracta?

 

[TD2K]

It's from the entrance.