Cicli a vapore rigenerativi testo

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Exercise: regenerative steam cycle Consider the ideal superheated steam cycle with one direct contact regenerator shown in the figure. Expansion is divided in a high pressure turbine (HPT) and a low pressure turbine (LPT). Between the two turbine sections, stream A is bled at the same pressure of stream 2 exiting the low pressure pump. The following data on the cycle are given: • No pressure drops in boiler and heat exchangers (pC=p3; p2=pA=pB; p1=p4) • Ideal pumps and turbines (hydraulic and isentropic efficiencies equal to 1) • Ideal motor/generator (pump/turbine motor/generator mechanical-electric efficiency equal to 1) • Evaporation pressure: p3 = 80 bar • Condensing Temperature: T4 = 30°C • Steam flow rate at HPT inlet: m3 = 1 kg/s • Steam temperature at HPT inlet: T3 = 450°C It is required to: • Draw a graph of the net efficiency of the cycle as a function of the regenerator pressure and find the optimal regeneration pressure maximizing the cycle efficiency. • Draw a graph of the second law efficiency losses as function of the regeneration pressure. In particular, draw the curves of the losses in the boiler, in the regenerator and the total losses. For this calculation, consider: o ambient temperature T0 equal to the condensing temperature o heat introduced in the cycle from an ideal hot source at the same temperature of the maximum steam cycle temperature. NOTE: TO SOLVE THIS EXERCISE (AND THE FUTURE PRECEPTS), IT IS STRONGLY SUGGESTED TO USE THE EXCEL ADD-INS FOR THE CALCULATION OF THE THERMODYNAMIC PROPERTIES OF WATER THAT CAN BE DOWNLOADED FROM BEEP ENERGY SYSTEMS SITE (SOFTWARE PAGE). 2 4 3 B A D HPT LPT 1 C