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hw_Rankine_Q_A

# hw_Rankine_Q_A - Problem Set Rankine Cycles Problem 1...

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Center for Advanced Energy Systems Michael R. Muller, Director 640 Bartholomew Road, Piscataway NJ 08854 (908) 644-8469 FAX: (732) 445-0730 [email protected] http://caes.rutgers.edu Problem Set: Rankine Cycles Problem 1 : Calculate the thermal efficiency of a simple Rankine cycle for which steam leaves the boiler as saturated vapor at 3 x 10 6 N/m 2 and is condensed to saturated liquid at 7000 N/m 2 . The pump and turbine have isentropic efficiencies of 0.6 and 0.8, respectively. The pump inlet is saturated liquid. Solution : ( ) ( ) 73 . 0 7167 . 7 559 . 0 1878 . 6 1878 . 6 s J/g 2636 168 04 28 h h Q Pa M [email protected] 2804 J/g 168 3 6 . 0 007 . 1 163 ; J/g 163 3 , 4 3 2 3 in 3 2 1 2 1 = = + = = = = = = = = + = Δ + = = χ fg f s s x s h h W h h P v h h h so ( )( ) ( )( ) ( ) ( ) ( ) ( ) % 5 . 26 2636 / 5 704 704 8 . 0 880 1924 2804 8 . 0 J/g 1924 2572 73 . 0 163 27 . 0 4 3 4 = = = = = = = + = η η h h W h Problem 2 : A Rankine-cycle power plant has one stage of reheat. The turbine inlet is 3 x 10 6 N/m 2 at 500 ° C. After expansion to 0.5 x 10 6 N/m 2 the steam is reheated to 500 ° C and expanded in a second turbine to a condenser pressure of 0.007 x 10 6 N/m 2 . The steam leaves the condenser as saturated liquid. Calculate the cycle efficiency, using a pump efficiency of 0.6 and turbine efficiencies of 0.8. Solution : 1)

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