This problem uses the standard reciprocating compressor volumetric efficiency equation (found in the Guidebook or the SPE Handbook Series). It can be difficult to recognize this, though, when you are merely asked for a gas rate.
It's fairly plug-n-chug once you have the necessary equation. The only trick? "L" (gas slippage) is not given so you must draw on experience assuming it's between 0-5%. When I did this problem I used 0%, then 5%, and found both gave the same answer "B": (A) 7.4 SCF/min
(B) 8.4 SCF/min
(C) 9.4 SCF/min
(D) 6.4 SCF/min.
I am having trouble with a part of this formula.
ReplyDeleteIn the reference guide by SPE, and in Ken Arnold's book it is given as:
Ev= 96-R-C{[R^(1/k)(Zs2/Zd2)]-1}-L
In your reference guide and I found in Petrowiki as:
Ev= 96-R-C{R^(1/k)[(Zs2/Zd2)-1]}-L
The difference is that in first equation 1 is subtracted from R^(1/k)(Zs2/Zd2) and in the second equation 1 is subtracted from Zs2/Zd2 and then multiplied by R^(1/k)
I don't have the Book3 in the HS. Would much appreciate if you could confirm the correct equation.
What version of Guidebook do you have?
DeleteCompressor manufacturers lack agreement on this equation.
DeleteFor this reason I just use the SPE VIII P291, which estimates Ev exactly as the Guidebook shows. When in doubt on the exam, go with SPE, even if you disagree with it in practice :-).
Now THAT would be a good question for an exam: What factor typically has the greatest effect on making Ev less than unity? A) Gas heated when entering the cylinder; B) ring and valve leakage; C) re-expansion of gas trapped in the clearance volume of the prior stroke; D) they are roughly the same. Answer: C. Hey, enjoy your weekend :-).
2018/#3
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