Question: Steam enters the first turbine stage of a vapor power cycle with reheat and regeneration at 32 MPa, 600C, and expands to 8 MPa. A portion of the flow is diverted to a closed feedwater heater at 8 MPa, and the remainder is reheated to 560C before entering the second turbine stage. Expansion through the second turbine stage occurs to 1 MPa, where another
Steam enters the first turbine stage of a vapor power cycle with reheat and regeneration at 32 MPa, 600C, and expands to 8 MPa. A portion of the flow is diverted to a closed feedwater heater at 8 MPa, and the remainder is reheated to 560C before entering the second turbine stage. Expansion through the second turbine stage occurs to 1 MPa, where another portion of the flow is diverted to a second closed feedwater heater at 1 MPa. The remainder of the flow expands through the third turbine stage to 0.15 MPa, where a portion of the flow is diverted to an open feedwater heater operating at 0.15 MPa, and the rest expands through the fourth turbine stage to the condenser pressure of 6 kPa. Condensate leaves each closed feedwater heater as saturated liquid at the respective extraction pressure. The feedwater streams leave each closed feedwater heater at a temperature equal to the saturation temperature at the respective extraction pressure. The condensate streams from the closed heaters each pass through traps into the open feedwater heater. Saturated liquid exiting the open heater is pumped to the steam generator pressure.
(a) sketch the layout of the cycle and number the principal state points.
(b) determine the amount of heat rejected in the condenser
Answer (1)
(a) Sketch the layout of the cycle and number the principal state points:State 1: Steam enters the first turbine stage (at 32 MPa, 600°C).State 2: Steam expands in the first turbine stage to 8 MPa.State 3: A portion of the flow is diverted to a closed feedwater heater (at 8 MPa). The rest is reheated to 560°C.State 4: The flow that is reheated enters the second turbine stage (at 8 MPa, 560°C).State 5: Expansion through the second turbine stage occurs to 1 MPa.State 6: A portion of the flow is diverted to a second closed feedwater heater at 1 MPa.State 7: The remainder of the flow expands through the third turbine stage to 0.15 MPa.State 8: A portion of the flow is diverted to an open feedwater heater (at 0.15 MPa), and the rest expands through the fourth turbine stage to the condenser pressure of 6 kPa.State 9: The steam reaches the condenser (at 6 kPa).State 10: Condensate leaves the condenser and is pumped to the steam generator pressure (32 MPa).(b) Determine the amount of heat rejected in the condenser:The heat rejected in the condenser can be found using the following process:Heat in the steam entering the condenser - The heat energy entering the condenser is the enthalpy of the steam at state 8 (before it enters the condenser).Heat out of the condenser - The heat energy leaving the condenser is the enthalpy of the liquid at state 10 (after the condensate is pumped).The amount of heat rejected in the condenser (Q_rejected) is:Q_rejected = h8 - h10Where:h8 = enthalpy at state 8 (before entering the condenser)h10 = enthalpy at state 10 (after exiting the condenser, saturated liquid at 6 kPa)To calculate this, you would need steam tables for enthalpies at various states (like 8 MPa, 560°C; 1 MPa, etc.) and the properties of water at the extraction pressures (6 kPa for the condenser). With these values, you can plug them into the equation above to get the heat rejected.
