240115 theoretical test

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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2022-23 15th January 2024 Prof. Andrea Giostri Time: 1 hour NAME and SURNAME:.................................................................................................................................................. COURSE and CFU:......................................................................................................................................................... MARK IN THE PRACTICAL PART (if you have done it in previous exam calls):……...................................... Instructions for the examination: 1) Clearly indicate your name on all the sheets you will deliver. 2) Give a synthetic and clear answer to as many questions as possible. The final score will be normalized according to the average results. 3) Talk with colleagues and / or cheating will cause the cancellation of the exam. OPEN QUESTIONS (points 18) 1. Considering a modern wind turbine, draw a typical speed triangle over the cross-section of the blade and explain why blades are twisted moving from the hub to the tip. 2a. For Mechanical Engineering students and Management Engineering students : Considering a plane solar thermal collector with a single glass, derive the efficiency of collector as function of its optical properties and the overall heat transfer coefficient. D raw the curve of efficiency as a function of temperature of the working fluid, identify and define the stagnation point. 2b. For Energy Engineering students (8 CFU): What power cycle would you adopt to exploit a superheated stream of geothermal vapor? Justify your answer and discuss the components characteristics used in the layout. MULTIPLE-CHOICE QUESTIONS (points 12) Answer to the following 15 questions. Select the box with correct answer (0.8 points if correct,…