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Unformatted text preview: at loss), and thus the entropy change of water will be 1.61 kJ/K.
Also, the entropy transfer at the boundary of the extended system will have the
same magnitude but opposite direction. This will result in an entropy generation
of 0.4 kJ/K. The negative sign for the entropy generation indicates that the reverse process is impossible.
To complete the discussion, let us consider the case where the surrounding
air temperature is a differential amount below 100°C (say 99.999 . . . 9°C) instead of being 25°C. This time, heat transfer from the saturated water to the
surrounding air will take place through a differential temperature difference rendering this process reversible. It can be shown that Sgen
0 for this process.
Remember that reversible processes are idealized processes, and they can be
approached but never reached in reality. Entropy Generation Associated with
a Heat Transfer Process
In Example 7–21 it is determined that 0.4 kJ/K of entropy is generated during
the heat transfer process, but it...
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- Spring '09