Es LM 06 09 22

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Politecnico di Milano School of Industrial Engineering Course Energy Systems proff. S. Consonni, E. Martelli, M. Romano - Academic Year 2021-22 Energy Systems LM – written test of 6 September 2022 page 1 of 2 Written Exam of 6 September 2022 - Problems - Time: 2 hours PLEASE NOTICE 1) Exam is open book, but computers and cell phones are NOT allowed. Talking with colleagues and/or copying will lead to the immediate cancellation of the exam. 2) Answer clearly ONLY to the questions posed by the problem sets. Even if correct, additional considerations and/or calculations will NOT be considered. 3) Fill this sheet with your name and return it together with your solutions. 4) Mark each sheet of the solution with your name and page number. 5) In addition to the points obtained for the solution of each problem, a bonus of max 1 point may be given based on whether the solution of each problem is complete, with clear details and explanations. Problem 1 (15 points) An industrial furnace burns natural gas to heat up steel bars. The flue gases leave the combustor at 1500 °C and they exit the furnace at 400 °C transferring 10 MW of thermal power to the steel bars. At the outlet of the furnace, the flue gases enter an air preheater. The following data are known: • ambient air temperature is 15°C; • Air is pre-heated to 250 °C in the air-preheater • Thermal losses and unburned fuel losses account for 0.6% of the fuel thermal power, on LHV basis • The natural gas molar composition is: CH4: 84%, C3H8: 2.3%, C4H10: 3.2%, CO2: 6.5%, N2: 4.0%; molar mass: 20.29 kg/kmo; LHV: 39.82 MJ/kg Requests: 1) draw the plant scheme (1 point) 2) determine the mass flow rate of air and natural gas (5 points) 3) determine the flue gas temperature at the outlet of the air-preheater (2 points) 4) determine…