ME200 - Lecture 331 - 11/15/2010...

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11/15/2010 1 Reversible Steady Flow Process ME 200 Thermodynamics I Purdue University , Dr. Tim Pourpoint – timothee@purdue.edu Lecture 33 November 15 th , 2010 Last Lecture: – Isentropic efficiency to compare ideal and actual process through steady flow devices Outline Today: ME 200 2 Reversible Steady Flow Process Next week: –E x am #3 on Wednesday (17 th ) from 8 to 9pm in WTHR 200 –C o v e r s lectures 1 to 32, emphasis on 2 nd law Solve SP32 BEFORE the exam , there will be an isentropic efficiency problem
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11/15/2010 2 • Entropy can be changed by: –Hea t transfer between system and surroundings (here modeled as isothermal) – Mass transfer (only for open systems (CVs) Entropy Balance SYSTEM S in Mass Heat Mass transfer (only for open systems (CVs)) – Irreversibilities (for all actual systems) S syst S gen 0 S out Mass Heat ME 200 3 Entropy Balance–Special Forms STEADY STATE: SINGLE INLET, SINGLE OUTLET: ME 200 4 CLOSED SYSTEM:
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11/15/2010 3 •Re ca l l moving boundary work formula Quasiequilibrium (QE) process • Valid for closed system undergoing quasiequilibrium compression or expansion •A quasiequilibrium process involves small departures from equilibrium •A l l states through which quasiequilibrium process passes ME 200 5 can be considered equilibrium states • Reversible process must proceed through a series of equilibrium states QE process is reversible • Otherwise there would a tendency for system to change spontaneously which is irreversible a quasiequilibrium process is ME 200 6 an internally reversible process
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11/15/2010 4 Reversible Steady Flow Work •C o n s i d e r the differential form of the first law for an open system at steady state: () qw d h d K E d P E  •F o r an internally reversible process: •S e c o n d Gibb’s (T ds) equation: •U s i n g definition of enthalpy and the above relations: int rev qT d s v Tds dh dP ME 200 7 v( ) ( ) rev wd P d K E d P E  22 1 21 2 1 2 11 vv rev P K E P E d P V V g z z    •Fo r incompressible fluid, we have: Special cases
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This note was uploaded on 12/11/2011 for the course ME 200 taught by Professor Gal during the Fall '08 term at Purdue University-West Lafayette.

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ME200 - Lecture 331 - 11/15/2010...

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