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Test_2_Solution - ENGR 30 F2009 Exam 2 Closed Notes Open...

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ENGR 30 F2009 Exam 2 11/09/2009 Closed Notes. Open Book. Do all the three problems. 1. Steam at 5 MPa and 350 0 C is being used to generate power in an adiabatic turbine whose exit pressure is 80 kPa and it comes out as saturated steam. How much power can we expect to generate using this turbine if steam flow rate through the turbine is 15 kg/s? What will happen to power generated per kg of steam passing through it if the turbine is not adiabatic and loses heat at a rate of 25 kJ/kg steam? Solution: Assume steady state operation, negligible changes in KE and PE. Governing equation: m h in – m h out + Q in – W out = 0 (a) Adiabatic operation --> Q in = 0 kJ/s m = 15 kg/s Inlet: Steam at 5 MPa and 350 0 C This is superheated steam since 350 0 C > T sat at 5 MPa From superheated steam tables h in = 3069.3 kJ/kg Outlet: Saturated steam at 80 kPa From pressure table for saturated water h g = 2662.4 kJ/kg at 75 kPa h g = 2675.0 kJ/kg at 100 kPa --> h out = 2662.4 + (2675.0 – 2662.4) (80-75)/(100-75) = 2664.92 kJ/kg Using governing equation: W out = (15 kg/s) (3069.3 – 2664.92) kJ/kg = (15 kg/s) (404.38 kJ/kg) = 6075.7 kJ/s or kW
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