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Unformatted text preview: €“9 Entropy Change of an Ideal Gas Air is compressed from an initial state of 100 kPa and 17Â°C to a final state of
600 kPa and 57Â°C. Determine the entropy change of air during this compression process by using (a) property values from the air table and (b) average specific heats. cen54261_ch07.qxd 11/18/03 9:57 AM Page 299 299
CHAPTER 7
T Pa 0k P2 = 600 kPa P2 T2 = 330 K 0
=6 2 AIR
COMPRESSOR P1 = Pa 100 k 1 P1 = 100 kPa
s T1 = 290 K FIGURE 7â€“34
Schematic and Ts diagram
for Example 7â€“9. SOLUTION A sketch of the system and the Ts diagram for the process are
given in Fig. 7â€“34. We note that both the initial and the final states of air are
completely specified.
Assumptions Air is an ideal gas since it is at a high temperature and low pressure relative to its criticalpoint values. Therefore, entropy change relations developed under the idealgas assumption are applicable.
Analysis (a) The properties of air are given in the air table (Table Aâ€“21). Reading sÂ° values at given temperatures a...
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This document was uploaded on 11/28/2012.
 Spring '09

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