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Unformatted text preview: elative to its critical-point value of
450°F. Therefore, the isentropic relations developed earlier for ideal gases are
applicable. T, R
P2 T2 = 780 R
P2 = ?
COMPRESSOR 4 psia P1 = 1 510 1 P1 = 14 psia
T1 = 510 R s FIGURE 7–40
Schematic and T-s diagram
for Example 7–11. cen54261_ch07.qxd 11/18/03 9:57 AM Page 304 304
FUNDAMENTALS OF THERMAL-FLUID 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 STEADY-FLOW 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 (quasi-equilibrium)
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 quasi-equilibrium work interactions lead to the maximum work output for work-producing devices and the minimum work input
for work-consuming 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