How do you find Z when the temperature line ends on the compressibility chart?

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SUMMARY

The discussion focuses on determining the compressibility factor (Z) using a compressibility chart when the temperature line ends. Specifically, it addresses scenarios where the reduced pressure (P_r) is 0.75 and the reduced temperature (T_r) is 0.96, highlighting that the T_r = 0.95 line does not extend to the required pressure. Participants clarify that values below the saturated vapor line cannot utilize the equation Pv = ZRT, and one user concludes that the value for T_r at P_r = 0.4 and Z = 0.6 is 0.86.

PREREQUISITES
  • Understanding of compressibility charts
  • Knowledge of reduced pressure (P_r) and reduced temperature (T_r)
  • Familiarity with the ideal gas law and the equation Pv = ZRT
  • Concept of saturated vapor lines in thermodynamics
NEXT STEPS
  • Study the construction and interpretation of compressibility charts
  • Learn about the implications of reduced properties in thermodynamic calculations
  • Research the behavior of gases below the saturated vapor line
  • Explore the relationship between compressibility factor (Z) and phase behavior
USEFUL FOR

Thermodynamic engineers, chemical engineers, and students studying phase behavior and compressibility in gases will benefit from this discussion.

zachdr1
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How do you find a value for Z using the compressibility chart when the temperature line you're trying to use ends?

For example, if you look at the compressibility chart and try to find a value for z with P_r = .75 and T_r = .96, you will notice that the line for T_r = .95 ends well before the pressure of .75. How do you find a value for Z in this situation?
 
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How many phases do you have to deal with when Pr, Tr are less than 1.0?
 
Bystander said:
How many phases do you have to deal with when Pr, Tr are less than 1.0?
1
 
Z.PNG
 
zachdr1 said:
Why do the Tr lines stop increasing in Pr after a while?
What do you think the dashed line in the figure represents?
 
Chestermiller said:
What do you think the dashed line in the figure represents?
the psuedo reduced specific volume

edit: i just realized you meant the saturated vapor line, anything below that line isn't a saturated vapor so I am assuming you can't use Pv=ZRT?

So if I asked you what the value for Tr is at Pr= .4 and Z=.6, what would your response be? This isn't a homework question by the way I just want to know what your response would be.
 
zachdr1 said:
the psuedo reduced specific volume

edit: i just realized you meant the saturated vapor line, anything below that line isn't a saturated vapor so I am assuming you can't use Pv=ZRT?

So if I asked you what the value for Tr is at Pr= .4 and Z=.6, what would your response be? This isn't a homework question by the way I just want to know what your response would be.
0.86
 

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