Example 4-2
Air with an initial temperature of 60°F and 14.7 psia is
compressed adiabatically and quasi-statically in a piston-
cylinder assembly. The mass of air is 0.066 lbm. If 1470
ft·lbf of work is done on the gas, find the final temperature
and pressure. Assume constant specific heats at 60°F.
Solution:
From the first law
U
Q
W
∆
=
−
Since the process is adiabatic
W
U
= −∆
(
)
2
1
v
W
mc
T
T
= −
−
Btu
CV(air,
60)
0.172
lbm R
v
c
T
=
=
=
⋅
2
1
v
W
T
T
mc
=
−
(
)
(
)
o
2
1Btu
1470ft lbf
778ft lbf
60 F
Btu
0.0661 lbm
0.172
lbm R
T
⎛
⎞
−
⋅
⎜
⎟
⋅
⎝
⎠
=
−
⎛
⎞
⎜
⎟
⋅
⎝
⎠
o
2
227 F
T
=
To find the final pressure, note that this is an adiabatic,

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