Exam 2020 06 04 Solution

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Department of Energy Politecnico di Milano Author Pag.1 of 11 Date 11/06/2020 Milan, 5th June 2020 Exam – Advanced Thermodynamic and Thermoeconomics Exam Simulation – Solutions Exercise 1. (15pt) Let’s consider a simple Energy Conversion System (ECS) enclosed in the control volume depicted in the figure (dashed line). The system is composed by 2 micro- CHP systems (a and b), and one absorption chiller (c), exchanging mass and energy flows between themselves and environment. Two micro- CHP systems receive primary energy from outside of the ECS’s boundary, producing heat and electricity. Electricity is used for the residential buildings, while Heat is used for the absorption chiller to provide cooling load for the buildings. Streams number 8 (flue gases) and 9 (steam leakage) are released to the environment without any additional cost. Table 1 State Ex [MW] 1 Primary Energy 100 2 Primary Energy 100 3 Heat 30 4 Heat 20 5 Cooling Load 20 6 Electricity 40 7 Electricity 20 8 Flue gases 5 9 Steam leakage 5 Table 2 unit cost of Fuel (c1, c2) [€/GJ] 8.333 Z_CHP a (Investment, O&M) [€/s] 0.2 Z_CHP b (Investment, O&M) [€/s] 0.125 Z_Absorption Chiller (Investment, O&M) [€/s] 0.1 Table 3 Chemical exergy Specific heat value (cp) @ 65°C Molar mass kJ/kmol kJ/kmol*K kg/kmol C2H6 (ethane) 1493900 57.9 30 CH4 (methane) 830200 37.7 16 Tamb 25°C Pamb 101325 Pa Absorption Chiller (c) ECS (Primary Energy) Micro CHP (a) Micro CHP (b) 2 (Primary Energy) 1 4 (Heat)3 (Heat) (Cooling Load) 5 Electricity Electricity 6 7 8 Flue gases Steam leakage 9 Department of Energy Politecnico di Milano Author Pag.2 of 11 Date 11/06/2020 With reference to the data provided by the tables, it is required to: a. Write analytically the exergy balance and derive of the rational and functional efficiency of each…