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Unformatted text preview: cen54261_ch07.qxd 11/18/03 9:57 AM Page 308 308
FUNDAMENTALS OF THERMAL-FLUID SCIENCES Substituting this relation into the preceding equation and dividing each term
by T, we obtain
T ds 0 since
T Also, T is the absolute temperature, which is always positive. Thus,
P1, T1 dwrev wrev wrev > wact dwact wact or TURBINE P2, T2 FIGURE 7–44
A reversible turbine delivers more
work than an irreversible one if both
operate between the same end states. Therefore, work-producing devices such as turbines (w is positive) deliver
more work, and work-consuming devices such as pumps and compressors
(w is negative) require less work when they operate reversibly (Fig. 7–44). 7–11 I MINIMIZING THE COMPRESSOR WORK We have just shown that the work input to a compressor is minimized when
the compression process is executed in an internally reversible manner. When
the changes in kinetic and potential energies are negligible, the compressor
work is given by (Eq. 7–53)
2 wrev, in 1 υ dP (7–56) Obviously one way of m...
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This document was uploaded on 11/28/2012.
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