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Unformatted text preview: nstant specific heats for air: T2
T1 FIGURE 7–39
The use of υr data for calculating the
final temperature during an isentropic
process (Example 7–10). s const. υ1
υ2 T, K t. =
υ2 co Isentropic
compression AIR
P1 = 95 kPa
T1 = 295 K
V1
=8
V2 k1 ns 2 FIGURE 7–38
Schematic and Ts diagram
for Example 7–10. 1
8 υ1 =
295 t. cons 1 s cen54261_ch07.qxd 11/18/03 9:57 AM Page 303 303
CHAPTER 7 The specific heat ratio k also varies with temperature, and we need to use the
value of k corresponding to the average temperature. However, the final temperature is not given, and so we cannot determine the average temperature in
advance. For such cases, calculations can be started with a k value at the initial or the anticipated average temperature. This value could be refined later, if
necessary, and the calculations can be repeated. We know that the temperature
of the air will rise considerably during this adiabatic compression process, so we
guess that the average temperature will be about 450 K. The k value at this anticipated average temperature is determined from Table A–2b to...
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This document was uploaded on 11/28/2012.
 Spring '09

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