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Unformatted text preview: Sin Sout or, in the rate form, as
Heat ·
Sin ·
Sout ·
Sgen ·
∆Ssystem 14243 FIGURE 7–61
Mechanisms of entropy transfer
for a general system. Tsurr
Immediate
surroundings SYSTEM
Q FIGURE 7–62
Entropy generation outside system
boundaries can be accounted for by
writing an entropy balance on an
extended system that includes the
system and its immediate
surroundings. 13
2 123 Rate of net entropy transfer
by heat and mass Rate of entropy
generation (kW/K) (7–77) Rate of change
in entropy ·
where the rates of entropy transfer by heat transferred at a rate of Q and mass
·
·
·
· s. The entropy balance
· are S
Q / T and S mass m
flowing at a rate of m
heat
can also be expressed on a unitmass basis as
(sin sout) sgen ∆ssystem (kJ/kg · K) (7–78) where all the quantities are expressed per unit mass of the system. Note that
for a reversible process, the entropy generation term Sgen drops out from all of
the relations above.
The term Sgen represents the entropy generation within the system boun...
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This document was uploaded on 11/28/2012.
 Spring '09

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