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Unformatted text preview: elative to its criticalpoint value of
450°F. Therefore, the isentropic relations developed earlier for ideal gases are
applicable. T, R
P2 T2 = 780 R
P2 = ?
780 2
Isentropic
compression He
COMPRESSOR 4 psia P1 = 1 510 1 P1 = 14 psia
T1 = 510 R s FIGURE 7–40
Schematic and Ts diagram
for Example 7–11. cen54261_ch07.qxd 11/18/03 9:57 AM Page 304 304
FUNDAMENTALS OF THERMALFLUID SCIENCES Analysis The specific heat ratio k of helium is 1.667 and is independent of
temperature in the region where it behaves as an ideal gas. Thus the final pressure of helium can be determined from Eq. 7–43: P2 7–10 I P1 T2
T1 k/(k 1) (14 psia) 780 R
510 R 1.667/0.667 40.5 psia REVERSIBLE STEADYFLOW WORK The work done during a process depends on the path followed as well as on
the properties at the end states. Recall that reversible (quasiequilibrium)
moving boundary work associated with closed systems is expressed in terms
of the fluid properties as
2 Wb P dV
1 We mentioned that the quasiequilibrium work interactions lead to the maximum work output for workproducing devices and the minimum work input
for workconsuming devices.
It would also be very insightful to express the work associated with steadyflow devices in...
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This document was uploaded on 11/28/2012.
 Spring '09

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