SpecialProblems32-34 - values and appropriate lines of...

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Special Problems for ME 200 – Fall 2011 Special Problems 32, 33, and 34 Due Monday, November 21, 2011 SP32: Air at 260 kPa and 747 C enters the nozzle of a turbojet engine with a velocity of 80 m/s and exits at 87 kPa. The isentropic efficiency of the nozzle is 92%. Consider variable specific heats for air. (a) Calculate the actual velocity (m/s) of air at the nozzle exit. (b) Determine the entropy generation (kJ/kg-K) in the nozzle. SP33: Carbon dioxide expands through a turbine from 0.9 MPa and 587 C to 0.1 MPa in a reversible, steady-flow process during which Pv 2 = constant. Consider variable specific heats for carbon dioxide. (a) Calculate the specific work (kJ/kg) during the expansion process. (b) Determine the specific heat transfer (kJ/kg) during the expansion process. (c) Show the expansion process on T-s diagram. Label the states, show temperature
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Unformatted text preview: values, and appropriate lines of constant pressure. SP34: Consider a coal-fired steam power plant that produces 300 MW of electricity and the electric generator has an efficiency of 96%. The power plant operates on the ideal Rankine cycle in which steam enters the turbine at 6 MPa and 440 C and the condenser pressure is 30 kPa. Assume that coal has a heating value (energy released when fuel is burned) of 29,300 kJ/kg and that 75% of the energy from coal is transferred to the steam in the boiler. (a) Calculate the required mass flow rate (kg/s) of coal. (b) Determine the overall plant efficiency (%) which represents the electricity generated divided by the rate of energy input from the coal. (c) Show the cycle on T-s diagram. Label the states, show property values, and appropriate lines of constant pressure....
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