Pressure Surge Equation for Gases 2

[Normusss]

Hi,
I was wondering if there was equation to solve for pressure surges for gases (natural gas in my case) on slow closing valves.

As the only ones I have found is for imcompressible fluids: P = 0.07VL / t + P1, where P1 is the inlet pressure, V is the flow velocity in ft/sec, t is the valve closing time in seconds and L is the upstream pipe length in feet.

Thanks.

 

[MortenA]

You wont have surges in gasses!

Best regards

Morten

 

[btrueblood]

...and I doubt that equation is valid for all fluids.

 

[stanier]

It may be correct o say dry natural gas under stable conditions may not give rise to surges. You can get surges from slugs of liquids in gas pipelines. That is why they invented "slug catchers".

Two phase flow will give you surges. This is a very complex subject.

 

[sheiko]

I wonder if there is a definitive and unique definition for surge? Could anyone give this definition?

"We don't believe things because they are true, things are true because we believe them."

 

[MortenA]

Stainer - he said gasses! I wont call it surges if its two phase. There are miles and miles of dry gas lines all over the world!

And dry gas in any condition will not "surge".

Then of course we could start to discuss surges in a compressor - thats the word surge - and gas.

I think we should help the guy. Not confuse matters.

From Wikipedia: surge and lurch, is the rate of change of acceleration; that is, the derivative of acceleration with respect to time, the second derivative of velocity, or the third derivative of position.

Thats pretty OK.

From Webster: to rise and move in waves or billows : swell <the sea was surging> Not so bad either.

IMHO surge = "water hammer". But when its a liquid but its not water its easier to use surge

Best regards

Morten

 

[stanier]

MortenA

I see where your coming from. The original posting said the gas was "natural gas". Until processed natural gas contains liquids. I was just trying to warn the original poster of issues that may have not been considered.