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ENERGY CONVERSION A 2016-17 Name/Lastname:__________________________________________ Code n.___________ Exam 27/06/2017 Exercise 1 (10 points) Consider a small-scale combined cycle for an industrial cogeneration application comprising two natural gas-fired gas turbines Siemens SGT-100 and a one-pressure level heat recovery steam cycle. The exhaust gases are cooled down in the steam generator first to 180°C by the recovery cycle, then to 90°C by the cogeneration bundle produc- ing hot water for the industry, and lastly they are dissipated at the stack. The heat recovery steam cycle is water- cooled and has an evaporation pressure of 20 bar. Each of the two gas turbines is characterized (ISO conditions) by:  gas turbine net electric power: 5.4 MWe,  gas turbine net electric efficiency: 30%,  exhaust mass flow rate: 20 kg/s,  turbine outlet temperature: 545°C, Knowing that the evaporation specific enthalpy of water at 20 bar is 1900 kJ/kg, please: i. clearly motivate the solution procedure and highlight the assumptions (1 point); ii. sketch the plant layout, the T-s diagram of the cycle and the T-Q diagram of the steam generator (2 points); iii. calculate the generated steam mass flow rate (2 points); iv. determine the wasted power of the evaporator and superheater (3 points); v. indicate without computing how the turbine outlet temperature changes in the hotter season (2 points). Exercise 2 (12 points) Consider the concentrated solar power plant illustrated in the figure. The working fluid is characterized by: MM=150 kg/kmol, cp0=1.5 kJ/kgK, cL=2 kJ/kgK, ρL=2500 kg/m3, Tcrit=250°C, pcrit=100 bar. The working fluid at the exit of the solar collectors (prior to the throttling valve) is at 17.5 bar and is subcooled (with respect to saturation) by 10°C. The throttling…