Determine the thermal efficiency of the cycle.

Question

  A steam power plant runs on an ideal reheat-regenrative-Rankine cycle. Details are given in Figure. Steam at turbine inlet is at 15 bars and 600⁰C. Condensor pressure is 0.10 bar. Steam exiting the HPT is at 40 bars. This steam is split in two parts, y and x. Part x is rehated at the same pressure to 600⁰C and sent to LPT. Part y is condensed completely in CFWH and it is pumped to 150 bars before it mixes with the flow at same pressure. A friction of steam, z, is extracted from LPT at 5 bars. Assume of steam, z, is extracted from LPT at 5 bars. Assume steam output of boiler as 1 kg/s for ease of computations. Determine:

(i) fraction y

(ii) fraction z

1. thermal efficiency of the cycle.

Given data is :

h1 = 191.81 kJ/kg h2 = 192.30 kJ/kg h3 = 640.09 kJ/kg h4 = 643.02 kJ/kg h5 = 1087.4 kJ/kg h6 = 1087.4 kJ/kg h7 = 1101.2 kJ/kg h8 = 1089.8 kJ/kg

h9 = 3155.0 kJ/kg h10 = 3155.0 kJ/kg h11 = 3674.9 kJ/kg h12 = 3014.8 kJ/kg h13 = 2335.7 kJ/kg Wpump 1 = 0.49 kJ/kg Wpump 2 = 3.83 kJ/kg Wpump 3 = 13.77 kJ/kg

 

R : Rehater HPT : High pressure turbine C : Condensor CFWH = Closed feedwater heat P1 : Pump 1 P3 : Pump 3

B: Boiler LPT : Low pressure turbine OFWH : Open feedwater heater MC : Mixing chamber P2 : Pump 2

Fig. 1 Schematic of steam power plant.