A regenerative Rankine cycle uses one open feedwater preheater and one closed feedwater preheater. Using the stream numbering from Fig. 5.6, and the specified conditions below, the plant capacity is to be 75 MW. Other constraints are as follows: The efficiency of each turbine stage is 85%; the pump efficiencies are 80%; and the feedwater leaving the closed preheater is 5°C below the temperature of the condensate draining from the bottom of the closed preheater. For the options below, calculate

(a) The flowrate of stream 1.

(b) The thermal efficiency of the plant.

(c) The size of the feedwater pumps (kW).

Options:

(i) The conditions are T₁ = 500°C, P₁ = 4 MPa, P₂ = 0.7 MPa, P₃ = 0.12 MPa, and P₄ = 0.02 MPa.

(ii) The conditions are T₁ = 600°C, P₁ = 4 MPa, P₂ = 1.6 MPa, P₃ = 0.8 MPa, and P₄ = 0.01 MPa.

Transcribed Image Text:

1 Boiler/ Superheater QH 9 A I 2 10 8 A II m 3 6 Pump III 5 4 Qc Condenser 11 Figure 5.6 Schematic for a system with a closed feedwater preheater, A, and an open feedwater preheater, B.