Unformatted text preview: dary
only (Fig. 7–61), and not the entropy generation that may occur outside the
system boundary during the process as a result of external irreversibilities.
Therefore, a process for which Sgen 0 is internally reversible, but not necessarily totally reversible. The total entropy generated during a process can be
determined by applying the entropy balance to an extended system that includes the system itself and its immediate surroundings where external irreversibilities might be occurring (Fig. 7–62). Also, the entropy change in this
case is equal to the sum of the entropy change of the system and the entropy
change of the immediate surroundings. Note that under steady conditions, the
state and thus the entropy of the immediate surroundings (let us call it the
“buffer zone”) at any point will not change during the process, and the entropy
change of the buffer zone will be zero. The entropy change of the buffer zone, cen54261_ch07.qxd 11/18/03 9:57 AM Page 323 323
CHAPTER 7 if any, is usually small relative to the entropy change of the system, and thus
it is usually disregarded.
When evaluating the e...
View Full Document