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Unformatted text preview: 1 (kJ/kg) (7–17) cen54261_ch07.qxd 11/18/03 9:57 AM Page 287 287
CHAPTER 7 To perform the integrations in Eqs. 7–15 and 7–17, one needs to know the
relationship between T and s during a process. One special case for which
these integrations can be performed easily is the internally reversible isothermal process. It yields
Qint rev T0 S (kJ) T 1
process (7–18) or 2 qint rev T0 s (kJ/kg) (7–19) where T0 is the constant temperature and S is the entropy change of the system during the process.
An isentropic process on a T-s diagram is easily recognized as a verticalline segment. This is expected since an isentropic process involves no heat
transfer, and therefore the area under the process path must be zero (Fig.
7–17). The T-s diagrams serve as valuable tools for visualizing the second-law
aspects of processes and cycles, and thus they are frequently used in thermodynamics. The T-s diagram of water is given in the appendix in Fig. A–9.
Another diagram commonly used in engineering is the enthalpy-entropy diagram, which is quite valuable in the analysis of steady-flow devices such as
turbines, compressors, and nozzles. The coordinates of an...
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This document was uploaded on 11/28/2012.
- Spring '09