Prelim_2_problem_2 - T 1 = 740 C , with NO INTERPOLATION....

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Prelim 2, Problem 2 Given: An ideal Rankine cycle without reheat and regeneration operates with a boiler pressure of 8 MPa and a condenser pressure of 0.1 MPa. The quality of the steam leaving the turbine and entering the condenser is 1; X 2 = 1. Find the temperature of the steam entering the turbine and the cycle efficiency. Solution: For an ideal Rankine cycle all process are reversible. Therefore the entropy is constant across the turbine (s 1 = s 2 ) and the pump (s 3 = s 4 ) and the pressure is constant in the boiler and the condenser. The cycle on a T-s diagram looks as follows: 1 2 3 4 T s X 2 =1 At 1: p = 8 MPa and s = s at 2. At 2: Water is saturated vapor at 0.1 MPa. From the tables, s 2 = 7.3594 kJ/kg K and h 2 = 2675.5 kJ/kg. For s 1 = 7.3594 kJ/kg K and p 1 = 8 MPa, from the super heat table,
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Unformatted text preview: T 1 = 740 C , with NO INTERPOLATION. For the cycle efficiency: 4 1 3 2 1 1 h h h h m Q m Q in out = = & & & & From the saturated water tables, h 2-h 3 =h g-h f =h fg =2258 kJ/kg From the superheat tables for T = 740 C and p = 8 MPa, h 1 = 3978.7 kJ/kg. h 4 could be obtained by interpolation from the compressed liquid tables. It is easier to use the results of section 6.9 regarding internally reversible steady-state flow work. kg kJ kg kJ kg kJ p p v h vdp h m W h h cv / 7 . 425 / 2 . 7 / 46 . 417 ) ( 3 4 3 3 4 3 3 3 4 = + = + + = + = & & Since liquid water is nearly incompressible it is ok to assume v = constant for integration. Substitution for the efficiency gives = 36.4%...
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This note was uploaded on 03/15/2010 for the course ENGRD 221 taught by Professor Staff during the Fall '08 term at Cornell University (Engineering School).

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