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P1 (kJ/kg · K) (kJ/K) The inequality part of the Clausius inequality combined with
the definition of entropy yields an inequality known as the increase of entropy principle, expressed as Or, on a unit-mole basis,
Sgen 0 (kJ/K)
s2 where Sgen is the entropy generated during the process. Entropy
change is caused by heat transfer, mass flow, and irreversibilities. Heat transfer to a system increases the entropy, and heat
transfer from a system decreases it. The effect of irreversibilities is always to increase the entropy.
Entropy is a property, and it can be expressed in terms
of more familiar properties through the T ds relations, expressed as
T ds du T2
C υ, av ln
s1 Ru ln υ2
υ1 (kJ/kmol · K) T2
C p, av ln –
s1 Ru ln P2
P1 (kJ/kmol · K) T1 Isentropic process:
T1 P dυ T2
T ds dh P2
P1 υ dP These two relations have many uses in thermodynamics and
serve as the starting point in developing entropy-change relations for processes. The successfu...
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This document was uploaded on 11/28/2012.
- Spring '09