08 07 19

Page 1

Department of Energy Politecnico di Milano Author F. Sanvito, E. Colombo Pag.1 of 8 Date 20/07/2019 Milan, 2nd June 2019 Exam – Advanced Thermodynamic and Thermoeconomics 08-07-2019 Please consider that the score breakdown within the exercise is a general indication. The final score include also an overall evaluation on the quality of the answer, the structure of the answer, the calculation and the explanation given Exercise 1. (15 pt) Politecnico di Milano (Energy Department) is developing a new heat transfer fluid named X-185 with advanced properties. The fluid is used in the Heat Exchanger (HE) of the plant presented in the figure. The institute wants to assess the maximum cost of the fluid (on exergy basis) given the target cost for electricity production by the turbine (T) equal to 0.5 €/kWh. Heat Exchanger takes in stream 1 that consists of CO 2. The purpose of Heat Exchanger is to increase the temperature of stream 1 in order to perform the following expan sion. The heat is provided by the new heat transfer fluid, X-185 (stream 4 and 5). Considering that: - The cost of compressed CO 2 (stream 1) is 0.176 €/kWh on exergy basis. - Stream 5 of X-185 is collected and stored again. - The expanded CO2 stream is t hen discharged into the environment with zero additional cost. - Environment conditions are 25°C and 1 atm. HE Ex2Ex1 Ex3 Ex5 Ex4 Wel T Table 1 Stream # [kW]iEx 1 23.06 2 57.03 3 2.56 4 50.33 5 2.14 W el 27.24 Table 2 model ,is T &OMi n vZ  ‐ € / h T_baseline 0.85 3 HE 5 t_eX250i 0.90 5 t_eHW‐75 0.75 2 Department of Energy Politecnico di Milano Author F. Sanvito, E. Colombo Pag.2 of 8 Date 20/07/2019 It is requested to: a. For each component write the ex ergy balance, compute exergy destructions, functional and rational exergy efficiencies. b. Considering…