Unformatted text preview: device is 8,
determine the final temperature of the air. SOLUTION A sketch of the system and the Ts diagram for the process are
given in Fig. 7–38. We note that the process is reversible and adiabatic.
Assumptions At specified conditions, air can be treated as an ideal gas. Therefore, the isentropic relations developed earlier for ideal gases are applicable.
Analysis This process is easily recognized as being isentropic since it is both
reversible and adiabatic. The final temperature for this isentropic process can
be determined from Eq. 7–50 with the help of relative specific volume data
(Table A–21), as illustrated in Fig. 7–39.
Process: isentropic
Given: υ1, T1, and υ2
Find: T2
T
.
.
.
T2
T1 .
.
.
.
.
. υr
.
.
.
read υ = υ2 υ
. r2 υ1 r1
.
.
read
υr1
.
.
. At T1 295 K: From Eq. 7–50: υ2
υ1
647.9 V2
V1
υr1 For closed systems: υr2 υr1 υ2
υ1 (647.9) 80.99 → T2 662.7 K Therefore, the temperature of air will increase by 367.7°C during this process. ALTERNATIVE SOLUTION The final temperature could also be determined
from Eq. 7–42 by assuming co...
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 Spring '09
 Thermodynamics, Energy, Entropy, entropy change

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