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Steam Power plant (Reheat)

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Homework Statement


vuKJEna.png


Homework Equations


Heat added, Qa (This I'm not sure how since the steam passed through a reheater before it enters the HPT. That is what I understand based on the problem above)
Work Net, Wnet
Efficiency, Wnet/Qa
Heat Rate, WP/EP (Not sure if that is the correct formula)

The Attempt at a Solution


First I made a T-S Diagram
w4NX6Ax.jpg


Based on the diagram above, I got all these enthalpy values.
OZzSVlg.png

h1 = h @ 3 MPa & 370C
h2 = h @ 0.7 MPa & s1
h3 = h @ 0.7 MPa & 500C
h4 = hf4 +x hfg4 (All values, 0.007 MPa)
where x = (s4 - sf4)/sfg4
h5 = hf @ 0.007 MPa
h6 = vf5 (P6-P5)
WP1 = h6-h5
ha = h @ 3 MPa and 500C

The WNet that I got is, 1485.491
For the Qa = (ha-h6) + (h3-h2) = 3959.022

Eff = .3752

Was not able to solve Heat Rate.

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I can't seem to understand how the answers shown in the problem was got. Please enlighten me. Thanks in advance!
 

Answers and Replies

  • #2
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It looks to me like h3 is wrong. It should be equal to h2 plus the heat given up by the high pressure stream between 500 C and 370 C. So, it should be about 3100 J/kg.
 
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Thank you for your reply.
Should I get the heat given up by using this formula?
Q=mcT
 
  • #4
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Thank you for your reply.
Should I get the heat given up by using this formula?
Q=mcT
Sure. Or you can get it from the steam tables as the ##\Delta h##. Both should give about the same answer.
 
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Sure. Or you can get it from the steam tables as the ##\Delta h##. Both should give about the same answer.
Hello,

We was informed that the label in the schematic diagram that was given to us was wrong. I adjusted my TS diagram based on the correction and tried to solve it again. Thankfully I got the answers now.

Thank you very much for your replies.
 

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