Thermodynamics Chapter 4 Review
4.1 Moving Boundary Work
Moving Boundary Work – work done through expansion and compression

analysis is done under quasiequilibrium status

the differential work done in thei matter is
as follows:
PdV
PAds
Fds
W
b
=
=
=
δ
=
∫
2
1
Pdv

this is why moving boundary work is called P dV work

The area under the curve of a PV diagram is equal to the total work done
over that process
Polytropic Process
Polytropic process
– doing actual expansion and compression process of gasses,
pressure, and volume:
n
CV
P

=

when this is substituted into earlier equation:
n
V
P
V
P
n
V
V
C
dV
CV
PdV
W
n
n
n
b


=
+


=
=
=
+

+


∫
∫
1
1
1
1
2
2
1
1
1
2
2
1
2
1
For an Ideal Gas: (PV = mRT)
n
T
T
mR
W
b


=
1
)
(
1
2
n not equal to 1
For special case where n=1 which is an isothermal process for an ideal gas:
=
1
2
ln
V
V
PV
W
b
4.2 Energy Balance for Closed Systems
 For any process the energy change is as follows:
dt
dE
E
E
E
E
E
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 Spring '08
 kostic
 Thermodynamics, Energy, Ideal Gasses

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