5_60_lecture9

5_60_lecture9 - MIT OpenCourseWare http://ocw.mit.edu 5.60...

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Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 5.60 Thermodynamics & Kinetics Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms . 5.60 Spring 2008 Lecture #9 page 1 Entropy For a reversible ideal gas Carnot cycle: rev Efficiency = w = 1 + q 2 rev = 1 T 2 q rev q 1 T 1 q 1 + q 2 = 0 v q rev = T 1 T 2 T The efficiency of any reversible engine has to be the same as the Carnot cycle: ( w ) ( w ) = = q 1 q 1 w Assume > (left Carnot engine less efficient cycle than Carnot cycle) T 1 (hot) T 2 (cold) q 2 q 1 w q 2 Some reversible engine Since the engine is reversible, we can run it backwards. Use the work (- w ) out of the Carnot engine as work input ( w ) to run the left engine backwards. Total work out = 0 (- w = w > 0) But ' > q w 1 > q w 1 w q 1 > q w 1 = w q 1 q 1 < q 1 since q 1 < 0, q 1 > 0 ( q 1 + q 1 ) > 0 This contradicts the 2...
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This note was uploaded on 07/31/2011 for the course CHM 170 taught by Professor Lemtayo during the Spring '11 term at MIT.

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5_60_lecture9 - MIT OpenCourseWare http://ocw.mit.edu 5.60...

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