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# How to calculate the saturated flow volume in natural gas (scf)

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## How to calculate the saturated flow volume in natural gas (scf)

(OP)
I would like to know calculation for the saturated flow volume in natural gas (scf).

I'm not sure, it should have water vapor factor or not.

and I don't know how to water vapor equation.

Please help to answer me.

thank you very much

### RE: How to calculate the saturated flow volume in natural gas (scf)

water in pounds/mmscf=(10^(3.5551-0.94283*LOG(psig+15)+0.01576*(temp in degrees F-31)))

### RE: How to calculate the saturated flow volume in natural gas (scf)

That equation deviates pretty dramatically from the ASTM data.  I've attached a graph of temperature vs. water content for four pressures between 14.73 psia and 2,000 psia.  As you can see, at atmospheric pressure the equation matches the ASTM data nearly perfectly from about 40F to about 90F.  A pretty good range to match in.  But the equation is semi-log linear and the data isn't.  By the time you get to 2,000 psia the lines only match at one point.

There are many empirical equations like that one floating around, all of them do a good job for a reasonable range of temperatures for a single pressure.  I did some serious curve fitting in MathCad a few years ago and came up with a ratio of two polynomials (6 constants) that did an OK job, but either worked at high pressure or at low pressure.  Not both.  So I went back to the drawing board and generated an equation for low pressure and a different equation for high pressure.  It matches really well over the whole range.  I don't share those equations, but you can generate you own with a couple of months of 20 hour days and seven day weeks (I tend to get obsessed with a problem like that).

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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### RE: How to calculate the saturated flow volume in natural gas (scf)

GPA is doing a new regression on the McKenna graphs and from the latest lab data.  There will be a new equation out soon.

### RE: How to calculate the saturated flow volume in natural gas (scf)

Will the GPA equation be semi-log linear?  Are they going to make pi=3.0 next?

David

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