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Flow coefficient of a gas valve - hoping Joe Galliera or similar can help

Question asked by Eamon Ronan on May 20, 2011
Latest reply on Jul 20, 2011 by Eamon Ronan

Hi folks,

This is pretty basic as as I've just started with Flow but am struggling with some fundamentals of what I need it to do.

Basically, I'm trying to set up Flow to replicate flow coefficient tests in semiconductor gas valves, as opposed to water, although granted they're similar enough.  My baselines are experimental test results - although some may be questionable.

I'm trying to get the CFD to match these - the CV result for say the demo ball valve will be different is done with water as opposed to a gas.

 

So the rig, or model now that I've SW, is simply set up to create a 1 psig pressure drop across a valve by 'choking' the downstream (e.g.  60 psig inlet and 59 psig outlet) and measuring the volume flow rate at the outlet.

 

What I'm really struggling with is firstly whether I need to 'do something' to the units/results to standardise them or change them becuase of a feature of SW Flow?

Secondly, the issue of whether to measure the volume flow rate at the inlet or the outlet.  If I've looked at threads and examples correctly, I see some done differently - maybe because water is incompressible.

And indeed thirdly, I just can't seem to find real explanations of some of the parameters, conditions, etc.  e.g.  I have been using Static Pressure at inlet and outlet, and just don't know if that's right because I don't really understand the differences between environmental, static and total on the set-up.  The same really for mass flow versus volume flow (that's where some issues on standardised measures really started to throw me).

 

I running away with changing some of the above and now back-tracking through the ANSI and SEMI specs ......but any advice even on where to get the best explanations of total/static/etc and whether there are nuances in the CFD that need units to be changed - it would be a great help.

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