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Unformatted text preview: 1016 A simple ideal Rankine cycle with water as the working fluid operates between the specified pressure limits. The maximum thermal efficiency of the cycle for a given quality at the turbine exit is to be determined. Assumptions 1 Steady operating conditions exist. 2 Kinetic and potential energy changes are negligible. Analysis For maximum thermal efficiency, the quality at state 4 would be at its minimum of 85% (most closely approaches the Carnot cycle), and the properties at state 4 would be (Table A5) K kJ/kg 7440 . 6 ) 8234 . 6 )( 85 . ( 9441 . kJ/kg 3 . 2274 ) 3 . 2335 )( 85 . ( 27 . 289 85 . kPa 30 4 4 4 4 4 4 ⋅ = + = + = = + = + = = = fg f fg f s x s s h x h h x P Since the expansion in the turbine is isentropic, kJ/kg 5 . 3115 K kJ/kg 7440 . 6 kPa 3000 3 4 3 3 = ⋅ = = = h s s P Other properties are obtained as follows (Tables A4, A5, and A6), kJ/kg 31 . 292 04 . 3 27 . 289 kJ/kg 04 . 3 m kPa 1 kJ 1 kPa ) 30 3000 )( /kg m 001022 . ( ) ( /kg m 001022 . kJ/kg 27 . 289 in p, 1 2 3 3 1 2 1 in p, 3 kPa 30 @ 1 kPa 30 @ 1 = + = + = = ⋅ = = = = = = w h h P P w h h f f v v v Thus, kJ/kg . 1985 27 . 289 3 . 2274 kJ/kg 2823.2 31 . 292 5 . 3115 1 4 out 2 3 in = = = = = = h h q h h q and the thermal efficiency of the cycle is...
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 Spring '10
 CHEN
 kJ/kg, Gas turbine, Combined cycle, Qin

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