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Unformatted text preview: Thermodynamics I Lecture 25: Clausius inequality, Entropy, increase in entropy principle Paul E. Sojka Summer 2011 This Lecture Clausius inequality usage Entropy The increase in entropy principle Entropy Entropy is a property, BUT A NON CONSERVED ONE Its a natural result of the 2 nd Law Clausius Inequality Clausius inequality will be used to develop entropy ,, irrevC rev HH b HCHC QQ QQ Q TT TT T =<= & Clausius Inequality (contd.) Consider the following: There are two cycles between states 1 and 2 c Cycle 1: A and C (both internally reversible) c Cycle 2: B and C (both internally reversible) Does the Clausius integral depend on the path? No! Its zero in both cases. SO ITS A PROPERTY! Entropy c We define the property entropy based on a reversible heat transfer process: c For a closed system c For a thermal reservoir nt.rev. Q dS T = 2 21 1 nt.rev. Q SSS T == , HC RHC HC QQ SorT T TT =+ c o n s t a n Entropy Generation 2 1 1 R Q S T  21 12 brevirrev QQQ TT T + & Consider two paths, one irreversible and one internally reversible, connecting states 1 and 2. Write Clausius inequality for the cyclic process R I 1 2 12 21 21 rrevirrev QQ SS TT = + Entropy Generation (contd.)Entropy Generation (contd....
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 Summer '08
 GAL

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