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Unformatted text preview: Thermodynamics I Lecture 27: Entropy balances Paul E. Sojka Summer 2011 Last Lecture c Ideal gas entropy changes This Lecture Closed system entropy balance Open system entropy balance Closed system entropy balance For closed systems, entropy change occurs only by: entropy transferdue to heat transfer at the system boundary entropy generationdue to irreversibilities within the system Closed system entropy balance Entropy balance for closed systems: 21 2 1 j j j system e SSS Q T ==+ Change in system entropy between given states Entropy transfer due to heat exchange at all j boundaries (dont forget boundary temperature) Entropy generation due to irreversibilities within the system Closed system entropy balance W Turbine 2 Turbine 1 W Turbine 2 Turbine 1 Q 1 , T 1 Q 2 , T 2 Q 3 , T 3 Q 4 , T 4 Thermal reservoir entropy balance 2 21 1 j ystemg eng en j jR Q Q SSSS TT ==+=+ Thermal reservoir at T R Q , reservoir genreservoir S S = = ntropy balance eversible isothermal process 21 systemg en sat Q SSSS T==+ at = Thermal resv at T R Q Thermal resv at T R Closed system entropy balance...
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This note was uploaded on 09/26/2011 for the course ME 200 taught by Professor Gal during the Summer '08 term at Purdue UniversityWest Lafayette.
 Summer '08
 GAL

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