Thermodynamics: Pass-out Turbine Question

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Discussion Overview

The discussion revolves around a question related to a pass-out turbine in thermodynamics, focusing on the methods and equations used to calculate power output. Participants are seeking clarification on their approaches and the parameters involved in the problem.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about their method and seeks validation of their approach to the problem.
  • Another participant questions the understanding of specific parameters and equations used in the calculations, particularly regarding h5, Vu, and their significance.
  • A participant proposes a specific equation for calculating power output but expresses doubt about the correctness of their equations for parts (b) and (c) of the problem.
  • There is a request for clarification on the rationale behind the proposed equations and a suggestion for a complete flow diagram to aid understanding.

Areas of Agreement / Disagreement

Participants generally express confusion and uncertainty about their methods and the parameters involved, indicating that multiple competing views and interpretations remain unresolved.

Contextual Notes

Participants have not fully defined all parameters or assumptions, and there are unresolved questions regarding the application of equations for different parts of the problem.

PaxFinnica96
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Homework Statement
Steam at 30 bar and 500°C enters a pass-out turbine at a rate of 18000 kg h–1. The bulk of this steam is expanded isentropically to a condenser pressure of 0.03 bar, but 32% is bled from the turbine at a pressure of 3 bar for process heating. If the condensate from the process heater is directly pumped back to the boiler, find:
a) Power output from the turbine
(b) the rate of process heating
(c) the efficiency of the plant.
Relevant Equations
m=Qp1/Qp2
Q=m_p (h2-h5)
η=(Qs-Q)/q
Hello Physics Forums,
I have been struggling with this question for some time now and I'm not sure my method is correct - please see attached.
Any help you can give to check I'm on the right lines would be very much appreciated!
Cheers, C
 

Attachments

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I don't understand what you're doing in the section starting with h5=hu-wp, and I don't understand what the parameters represent. Also Vu, and what it's used for.
 
Hi Chestermiller, I'm not really sure where I was going with this either and as a result I'm quite confused on where to begin.
I think I should use:
p=1((h1-h4)+(1-0.32)(h4-h2))
to find the power output from the turbine but not sure if I've used the correct equations for (b) and (c).
 
PaxFinnica96 said:
Hi Chestermiller, I'm not really sure where I was going with this either and as a result I'm quite confused on where to begin.
I think I should use:
p=1((h1-h4)+(1-0.32)(h4-h2))
to find the power output from the turbine but not sure if I've used the correct equations for (b) and (c).
If h4 is the 3 bars and h2 is the 0.03 bars, then I agree.

Please say in words your rationale for parts b and c. Also, a complete flow diagram would be helpful.
 

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