A modified Rankine cycle uses reheat and one closed feedwater preheater. The schematic is a modification of Fig. 5.7 obtained by adding a reheater between the T-joint and turbine II. Letting stream 3 denote the inlet to the reheater, and stream 3a denote the inlet to the turbine, the conditions are given below. The plant capacity is to be 80 MW. Other constraints are as follows: The efficiency of each turbine stage is 85%; the pump efficiency is 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 pump (kW);

Options:

(i) T₁ = 500°C, P₁ = 4 MPa, P₂ = 0.8 MPa, T_3a = 500°C, P₄ = 0.01 MPa.

(ii) T₁ = 600°C, P₁ = 4 MPa, P₂ = 1.2 MPa, T_3a = 600°C, P₄ =  0.01 MPa.

Transcribed Image Text:

1 Boiler/ Superheater Q 7 I Feedwater Preheater 2 8 6 3 II Condenser Pump 5 4 9 Figure 5.7 Regenerative Rankine cycle for Example 5.3.