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Politecnico di Milano Department of Energy - School of Industrial Engineering Course Energy Systems prof. S. Consonni, E. Martelli, M Romano - Academic Year 2017/18 Written Exam 21 January 2019 Theoretical Questions ‐ Time: 1.00 h PLEASE NOTICE 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. Even if correct, additional considerations will NOT contribute to the final grade – and you have NOT enough time! 3) Fill this sheet with your name and return it with your answers. 4) MARK EACH SHEET OF YOUR ANSWERS with YOUR NAME AND PAGE/SHEET NUMBER. 5) WRITING AND SHEET/PAGE SEQUENCE MUST BE LEFT TO RIGHT AS USED IN WESTERN COUNTRIES. 6) The final grade is the sum of the points assigned to the answer of each question plus a bonus of max 3 points. The bonus will be given based on completeness, clarity and details of the explanations. 7) Wherever possible, support your statements with clear drawings and/or graphical representation 8) ORGANIZE YOUR ANSWERS CLEARLY: ANSWER TO 1.a; ANSWER TO 1.b, ETC. FIRST NAME…………………………………….......……FAMILY NAME………………………………………………….. Question 1 (16 points) Consider a basic vapor compression reversed cycle (i.e., Rankine cycle for refrigeration): a. draw the T‐s and p‐h diagrams; b. write the expression of COP for both a refrigeration system and a heat pump system; c. list the main parameters that affect the COP of the cycle; d. describe the effect of condensate subcooling on COP and refrigeration power; e. describe the double‐stage refrigeration cycle drawing the plant scheme, the T‐s and p‐h diagrams, and explaining the reasons why such double stage cycl e can exhibit better performances than…