Pressure Loss accross a valve

[DW1006]

Afternoon,

I am trying to work out how you calculate the pressure loss across a valve?

We have a stored volume pressure at 600psi contained in 6 vessels, 90ft long 6ft internal diameter and around 45mm thick.
On demand, we can release all this to atmosphere in a matter of around 40 seconds.
The air passes through valves, and when this happens, we can see a pressure loss across the valve?

two questions.
1) how do you calculate pressure loss across a valve
2) what could cause be causing the pressure loss.

 

[LittleInch]

It's called valve CV - look it up.

Why do you want to waste all that energy?

A lot depends on what type of valve you have. A full bore Gate or ball valve should have the equivalent CV of the some size piece of pipe, but many are either reduced bore or have other flow restrictions.

This will though be sonic, choked flow which bring a whole heap of other issues.

Your mass flow rate will gradually drop as the internal pressure reduces, but exit velocity will be the speed of sound.
Your 40 seconds sounds very low and what do you mean by "all". You could probably get down to 20 or 30psi, but the last bit takes a loooooong time.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DW1006]

Hi, thanks for the reply, some good stuff for me to look into. Sorry, I should have said, we are operating a High speed Wind Tunnel blow down facility. Running up to Mach 3.7

By all, I was referring to clean dry compressed air. However, you are right, we don't completely drain down to zero, we generally take it down to as low as 500kPa (72.5psi thereabouts) from 4000kPa (580psi)

 

[LittleInch]

"a High speed Wind Tunnel blow down facility. Running up to Mach 3.7"

No idea what that is or how you get > 1Mach

How does that work?

what type of valves?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DW1006]

This facility conducts aerodynamic testing to assess the stability and control of aircraft. Scaled models of the aircraft are equipped with strain gauges, and as the tunnel is operated at different Mach numbers, the model is systematically traversed to collect data on its performance. The Mach number is maintained consistently throughout the test run, achieved by adjusting valve positions in conjunction with the tunnel's geometry to ensure the desired airflow speed. The facility has advanced control systems to precisely adjust airflow parameters, including velocity and pressure, to simulate different operating conditions accurately. Cant really say much more than. Its other valves within the system we sometimes see pressure drops. We have various types, control valves, manual and slam shut.

 

[GBTorpenhow]

Its a big supersonic nozzle.

You will have to be far more specific with your questions to get useful answers, OP.

https://www.emerson.com/documents/a...zing-standardized-method-fisher-en-140724.pdf

https://dam.bakerhughes.com/m/47616...lve-Sizing-Handbook-GEA19540A-English-pdf.pdf

https://cti-ct.com/images/cti/template/Control-Valve-Sizing.pdf

 

[DW1006]

Cheers for the links GBTorpenhow. That's a very good representation as well.