Unformatted text preview: ination of entropy change of a system during a process
involves evaluating entropy of the system at the beginning and at the end of
the process and taking their difference. That is,
Entropy change Entropy at final state Entropy at initial state or
∆Ssystem Sfinal Sinitial S2 S1 (7–69) Note that entropy is a property, and the value of a property does not change
unless the state of the system changes. Therefore, the entropy change of a
system is zero if the state of the system does not change during the process.
For example, the entropy change of steadyflow devices such as nozzles,
compressors, turbines, pumps, and heat exchangers is zero during steady
operation.
When the properties of the system are not uniform, the entropy of the system can be determined by integration from
Ssystem sdm sr dV (7–70) V where V is the volume of the system and r is density. Mechanisms of Entropy Transfer, Sin and Sout Entropy can be transferred to or from a system by two mechanisms: heat
transfer and mass flow (in contrast, energy is transferred by wo...
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This document was uploaded on 11/28/2012.
 Spring '09

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