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Unformatted text preview: ake the water in the cylinder as the system (Fig. 7–69).
This is a closed system since no mass crosses the system boundary during the
process. We note that the pressure and thus the temperature of water in the
cylinder remain constant during this process. Also, the entropy of the system
decreases the process because of heat loss.
Assumptions 1 There are no irreversibilities involved within the system boundaries, and thus the process is internally reversible. 2 The water temperature
remains constant at 100°C everywhere, including the boundaries.
Analysis (a) Noting that water undergoes an internally reversible isothermal
process, its entropy change can be determined from ∆Ssystem Q
Tsystem (100 600 kJ
273 K) 1.61 kJ/K T = 100°C 600 kJ H2O
Tsurr = 25°C FIGURE 7–69
Schematic for Example 7–21. cen54261_ch07.qxd 11/18/03 9:57 AM Page 330 330
FUNDAMENTALS OF THERMAL-FLUID SCIENCES (b) To determine the total entropy generation during this process, we consider
the extended system, which includes the water, the piston-cylinder device, and
the region immediately outside the system that experiences a temperature
change so that the entire boundary of the e...
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- Spring '09