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Thermodynamic Question- Equation Of State Oxygen

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#1 Student5642


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Posted 31 December 2018 - 01:41 PM

Freshman chemical engineering student struggling to get started on a homework question :


Plot the p-v-T diagram for oxygen, using an appropriate equation of state – identify critical regions and places on the diagram.


Anyone know what equation of state would be an appropriate place to start? Once I have this equation how do I then plot the relevant data? 



#2 Technical Bard

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Posted 01 January 2019 - 07:50 PM

Oxygen is a simple diatomic gas.  At low pressures and elevated temperatures it behaves like an ideal gas.  For a wider range, a cubic EOS like Peng-Robinson or Soave-Redlich-Kwong will be reasonably accurate.

#3 PingPong


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Posted 02 January 2019 - 06:20 AM

Student5642, you could use BWR equation of state. That should be more accurate as it uses more constants that were moreover determined in the past by fitting to experiments, while PR and SRK only use constants based on pc , Tc and acentric factor of each component.

Especially in the region around the critical point BWR should be more accurate than PR and SRK.

#4 latexman


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Posted 02 January 2019 - 07:22 AM

Normally, I would recommend going to http://webbook.nist.gov/ , but "Due to the fact that the [ U.S.] federal government is currently shut down, the website down.nist.gov will be unavailable until further notice."

#5 Art Montemayor

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Posted 03 January 2019 - 12:34 PM



I think the erudite PingPong is correct.


Since the USA Government NIST web page is presently shut down, perhaps the attached document will help you apply his recommendation.


Attached File  A Modified B-W-R EOS for Gaseous & Liquid Oxygen.docx   16.71MB   17 downloads


Attached File  A Modified BWR EOS for Gaseous & Liquid Oxygen.pdf   1.91MB   28 downloads

#6 Art Montemayor

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Posted 09 January 2019 - 02:34 PM

To all interested members:


I've noted that there were significant downloads of the original pdf on the B-W-R EOS I submitted relative to the number of thread participants and due to the interest shown, I've edited and formatted the pdf into Word for Windows as a document that reads a lot better and is easier to grasp and study than the pdf.  I've attached this Word document (although lengthy) to the original submittal.


I hope this helps you all in a positive way to understand the work input that was done back in 1978 by NASA.  Happy New Year.

#7 Nikolai T

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Posted 10 January 2019 - 09:04 PM

Dear Art,


Thank you. Happy New Year!



Kind regards,


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