5 replies to this topic

[HMAlmosa]

Do you know of a formula that I can insert in Excel to calculate gas compressibility factor. I have looked in many places, but could not find one. I finally developed a complicated formula through curve fitting the compressibility factor charts in GPSA as a function of reduced pressure and temperature (Pr & Tr). Can you help with this one?

[latexman]

There must be dozens of Equation of States (EOS) you could use to estimate Z. The van der Waals equation is simple and general. The most widely used two parameter Equation of State is the Redlich-Kwong equation. Check in your MEB and thermo textbooks, Perry's Handbook, and Sherwood, Reid , and Prausnitz.

[joerd]

There's even one on this site: www.cheresources.com/srk.xls

[ankur2061]

Hello,

Please look into the following thread where I have posted an excel sheet to calculate the compressibility factor Z :

http://www.cheresour...?showtopic=4731

Regards,
Ankur

[iceman]

The best method is as you mentioned using reduced pressure and temperature. Then finding the compressibilty factor from charts. The reason being the charts have been built using experimental data i.e more accurate than any method for calculating the factors. Usually this is straight forward once you know the Tr/Pr values with final aim being of calculating the volume of a real gas. It gets a little bit involved (but only just that) when trying to find the pressure or temperature of a known volume of a gas. Then as you mentioned you end up with an equation of the type
Z= K x P or Z= K x T where K is a numerical figure obtained from setting up the equation.
Plotting this in the experimental chart and finding your pressure or temperature at the intersection of this plotted straight line through the origin with slope K with the Z curve of either the known pressure or temperature as the case may be. Assuming either the pressure ot temperature is unknown then V,n,T,R are known and the equation becomes as above.

I hope this of some benefit and if known then at least to confirm it.

regds
iceman

Do you know of a formula that I can insert in Excel to calculate gas compressibility factor. I have looked in many places, but could not find one. I finally developed a complicated formula through curve fitting the compressibility factor charts in GPSA as a function of reduced pressure and temperature (Pr & Tr). Can you help with this one?

[breizh]

In case you need more input :
http://www.cheng.cam...hermo/pure.html

regards
Breizh