Supersonic flow

[Ninja1980]

I’ve just been asked the question if supersonic flow could occur at any point in the plant we are currently designing. I explained at no point the speed of fluid could exceed Mach 1 (chocked flow) unless flow passes though a convergent-divergent nozzle with sonic flow at the throat and the correct downstream pressure to create supersonic flow in the outlet. This is the same principle used jet engines.

However, this has got me thinking, could supersonic flow could occur though a blowdown valve or PSV? Assuming the back pressure was in the correct limitations, could this act as a De Laval nozzle???

 

[davefitz]

Yes.Sort of . Older tech papers that analyse the flow profile of steam exiting the steam dump to condenser sparger nozzle claim hypersonic flow fields of mach no of 6, down stream of the sharp edged holes.

 

[EGT01]

Here's a reference that suggests it could occur in relief valves.

http://www.freepatentsonline.com/4979540.html?query=PN/4979540+OR+4979540&stemming=on

 

[owg]

Sonic orifices are commonly used to meter purge steam to equipment in fouling service. If you have 150 psig steam for example and you size a nozzle to provide a purge to an area that typically runs in the say 20-50 psig range, the flow through the orifice will be at sonic or critical velocity and will be constant as long as the downstream pressure stays in the expected range.

HAZOP at

http://www.curryhydrocarbons.ca

 

[sailoday28]

Bursting of a rupture disc can lead to supersonic flow. This is a transient condition and probably will die out in the steady state.
Regards