SP26 to 28 – Hints
This problem is almost the same as Example 26.2 covered in class  see solutions for it on Blackboard
(Home Page › Solved Examples)
System sketch:
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Goal here is to show whether or not the increase of entropy principle is violated in this case.
This means, you must calculate the total entropy generation during the process.
i.e.: if
S
air
+
S
surroundings
=
gen
0, claim is true, otherwise it is false.
Note that
S
surroundings
makes use of:
q
surroundings
, in magnitude equals the heat rejected from the system
T
surroundings
,
the temperature outside the system, given to you as 27
C
You can determine
q
air
from energy balance, basic equation for
U
and assumptions
Negative
q
air
indicates heat rejected from the system during the compression process
From the surrounding point of view, this heat is added =>
q
surroundings
= q
air
Adding
S
air
and
S
surroundings
leads to a negative total entropy generated => IMPOSSIBLE!
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 Fall '08
 GAL
 Entropy, Adiabatic process, Home Page, total entropy generation

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