240126 Theory

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Politecnico di Milano Energy Conversion Technologies prof. Emanuele Martelli - Academic Year 2023-24 page 1 of 1 Written Exam of 26 January 2024 - Theory Time: 45 minutes 1) Books, lecture notes, cell phones are strictly forbidden. Using them or talking with colleagues and/or copying will lead to the immediate invalidation 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. Energy Conversion Technologies Question 1 (18 points) - Provide the definition of excess of air of a combustion process (2 points) - Provide the definition of the adiabatic flame temperature of a combustion process (2 points) - Write the equation to compute the adiabatic flame temperature as a function of the excess or air. (6 points) - Explain the criteria used to determine the excess of air for a boiler and a gas turbine. (8 points) Question 2 (18 points) - Draw the cycle scheme and the T-s diagram of a real superheated steam cycle (3 points) - Explain and motivate the effects of superheating on the efficiency of the cycle. (4 points) - Draw the cycle scheme and T-s diagram of a real saturated Rankine cycle with dry- expansion fluid and regeneration (e.g., an Organic Ranking Cycle using toluene as working fluid) (3 points) - Explain and motivate the effects of regeneration on the efficiency of the cycle. (4 points) - Explain and motivate for which applications Organic Rankine Cycles are preferred to steam cycles (4 points).