Determine...
a.) The thermal efficiency of the cycle.
b.) The mass flow rate of water/steam through the boiler in kg/h. if the net power output of the cycle is 320 MW.
Tuesday, May 22, 2007
HW #9, P4 - Special Rankine Cycle with Reheat and Regeneration - 8 pts
A power plant operates on a regenerative vapor power cycle with one closed feedwater heater. Steam enters the high-pressure turbine at 120 bar and 520oC and expands to 10 bar, where some of the steam is extracted and diverted to a closed feedwater heater. Condensate leaves the feedwater heater as a saturated liquid at 10 bar and then passes through an expansion valve before it is combined with the effluent from the low-pressure turbine. This combined stream flows to the condenser. The boiler feed leaves the feedwater heater at 120 bar and 170oC. The condenser pressure is 0.06 bar. Each turbine stage has an isentropic efficiency of 82%. The pump is essentially isentropic.
Determine...
a.) The thermal efficiency of the cycle.
b.) The mass flow rate of water/steam through the boiler in kg/h. if the net power output of the cycle is 320 MW.
Determine...
a.) The thermal efficiency of the cycle.
b.) The mass flow rate of water/steam through the boiler in kg/h. if the net power output of the cycle is 320 MW.
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7 comments:
For clarification, the only purpose of the FWH is to preheat the boiler stream? Is this the only regeneration part of this cycle?
I need help finding the enthalpy of stream 9. So far I've used the mass balance equation for the mixer, the 1st Law for the regenerator, and the 1st Law for the Mixer but I still seem to need another equation since I don't know any of the mass flow rates or the enthalpy of stream 9. Could I have a hint please?
Scattante:
Yes. The Closed FWH is the regenerator. We developed the flow diagram for this process in class.
Sparticus:
You have gotten to the hard part !
By applying the MIMO 1st Law to the mixer, you get H9 = fxn(m4/m1,m5/m1) where m4/m1 is the fraction of the fluid flow that goes to the open FWH and m5/m1 is the fraction of the flow that goes to the LP turbine.
You can determine the flow fractions by applying the 1st Law and a mass balance to the open FWH. Then, come back the 1st Law on the mixer to get H9.
You can also divide the numerator and denominator of the definition of thermal efficiency by m1. This allows you to express thermal efficiency in terms of one of the flow fractions, m5/m1. In this way, you can answer part (a) without using the 320 MW for the net power of the cycle.
It seems like we're missing some information to calculate H6 -- I have no idea how to get this quantity.
Anon:
Determine H6S using S6S = S3. Determine H6 from H6S using the isentropic efficiency of the turbine.
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