Question

Consider a reheat-regenerative vapor power cycle with two feedwater heaters, a closed feedwater heater and an open feedwater heater. Steam enters the first turbine at 8.0 MPa, 500°C and expands to 0.8 MPa. The steam is reheated to 500°C before entering the second turbine, where it expands to the condenser pressure of 10 kPa. Steam is extracted from the first turbine at 2 MPa and fed to the closed feedwater heater. Feedwater leaves the closed heater at 200°C and 8.0 MPa, and condensate exits as saturated liquid at 2 MPa. The condensate is trapped into the open feedwater heater. Steam extracted from the second turbine at 0.3 MPa is also fed into the open feedwater heater, which operates at 0.3 MPa. The stream exiting the open feedwater heater is saturated liquid at 0.3 MPa. The net power output of the cycle is 100 MW. If all the processes are reversible, Draw the system components, the T-s diagram, and determine (a) the thermal efficiency, (b) the mass flow rate of the steam entering the first turbine, in kg/h 6 10 12 13 State T (°C) P (MPa) 500 500 200 8.0 2.0 0.8 0.01 0.01 0.3 0.3 2.0 s (kJ/kg.K 6.7266 7.8692 8.1488 h (kJ/kg) 3399.5 3001.3 3481.33172.5 2494.6 191.81 561.43563.65 852.26 4 T 500°C Steam generator 0.8 MPa 8.0MPa r, = 500°C, 2 5 Condenser 10 kPa Closed heater heater 0.3 MPa T 200°C 2.0 MPa 10 12 13 Pump 2 Pump l Trap

Answer 1

Given data: - Stream enters the first turbine = 8 MPa Temperature = 500 degree c The condenser pressure = 10 kpa stream extracted from the first turbine = 2 Mpa Feed water levels closed heater = 200 degree c times 8 Mpa stream extracted from second turbine = 0.3 Mpa Net power output of the cycle = 100 Mw Find: - (a) Thermal efficiency (b) Mass flow rate of the stream entering the first turbine stream 1: - T_1 = 500 degree c, T_1 = 500 degree c P_1 = 8 Mpa h_1 = 3384.4 kJ/kg S_1 = 6.6586 kJ/kr] rightarrow From excepted water stream table stream 2: - P_2 = 2 Mpa S_2 = S_1 Now h_2 = 2953.5 kJ/kg \r\n stream 3: - P_3 = 0.7 Mpa, s_3 = S_1 From saturation water table. Saturation table is used as refer stream - 3 in the T - S curve S_F = 1.9925 kJ/kg - k