A power plant works with an ideal steam regenerative cycle. It consists of the following: a. A vapor turbine that ideally expands steam from 3.0 MPa and 400 oC to 10 kPa, after which the fluid goes to the condenser. b. Two extraction points in the turbine for the regenerative system, which are used as follows: i. First, steam is extracted at 0.8 MPa for a close FWH. ii. Second, steam is extracted at 100 kPa for an open FWH. iii. Condensate from the close FWH is drained through a trap to the open FWH and the water leaving the trap is saturated liquid. c. Two pumps, one is used to bring the water leaving the condenser up to 100 kPa for an open FWH, and the other one brings the feedwater up to 3.0 MPa. d. The flows from the extraction points in the turbine are controlled in such a way that the feedwater leaves the condenser, the open FWH, and the close FWH as saturated liquid.
NOTE: STATE 5 is a saturated liquid & please include a Pressure Volume Diagram
Calculate the thermal efficiency of the cycle and the specific net work for the following two cases:
1. This fully operational power plant, as described above.
2. After many years of operation of the power plant, a control valve (not shown in the figure) in the pipeline connecting the 1st extraction point and the closed FHW starts malfunctioning. It is decided to close it completely, which totally restricts any flow through that line, and subsequent lines. It is desired to keep operating the power plant while fixing the problem by adjusting the flow in the second point of extraction in order to still have as saturated liquid the feedwater leaving the open FWH.