Thus p1 t1 dwrev wrev wrev wact dwact wact or turbine

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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 wrev wact T qact T ds 0 since ds qact 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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