Gas Turbine TS Cycle: Understanding the Significance of Points 5-5b and 5b-6

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Discussion Overview

The discussion centers around the significance of specific points (5-5b and 5b-6) in a temperature-entropy (TS) diagram related to the gas turbine cycle. Participants are trying to understand the meaning and implications of these points in the context of thermodynamic processes, particularly in relation to combustion and heat exchange.

Discussion Character

  • Homework-related, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant expresses confusion about the significance of points 5-5b and 5b-6 in the TS diagram, noting clarity on other segments like 1-2 (compression) and 4-5 (regeneration).
  • Another participant suggests that understanding the difference between points 7 and 7b might help clarify the meaning of 5b, indicating a potential pattern in the diagram's structure.
  • A different participant proposes that if 6-7 represents ideal heat exchange, then 6-7b might represent a practical limit for that stage, implying that not all heat can be extracted in a heat exchanger.
  • One participant posits that 6-7 represents isentropic expansion in the turbine, while 6-7b indicates actual expansion, suggesting that point 5b may be relevant for efficiency considerations.
  • Another participant questions whether points 5b and 7b might refer to a different problem altogether, indicating uncertainty about their relevance in the current context.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the significance of points 5-5b and 5b-6, with multiple competing interpretations and uncertainties expressed throughout the discussion.

Contextual Notes

Participants note that certain segments of the TS diagram have not been encountered in examples provided by their lecturer, indicating potential limitations in their understanding or exposure to the material.

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Homework Statement


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Homework Equations


N/A

The Attempt at a Solution


I am confused what 5-5b and 5b-6 represent in the above TS diagram. I know that 1-2 is compression, 2-3 is cooling, 3-4 is compression and 4-5 is regeneration (since these are indicated in the block diagram) but as for 5-5b and 5b-6 it is less clear. I mean 5-6 is the combustion chamber but what is the significance of the 5-5b and 5b-6 segments? Why have they split it up like this?
 
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Looking over the diagram perhaps if you can explain what's different between 7 and 7b, you might have your answer for 5b?

Beyond this I can't assist; I haven't looked at thermo since my student days.
 
NascentOxygen said:
Looking over the diagram perhaps if you can explain what's different between 7 and 7b, you might have your answer for 5b?

Beyond this I can't assist; I haven't looked at thermo since my student days.
Thanks for your reply. Unfortunately, I don't get that part either lol. Haven't encountered it in examples provided by my lecturer so far.
 
My guess is that if 6-7 represents the ideal heat exchange, then perhaps 6-7b represents a practical best attainable for that stage. You can't extract all of the heat in a heat exchanger.

I think the image you attached might be too large, it spills out and forces the rest of the page into small size.
 
My view was that 6-7 represents isentropic expansion in the turbine and 6 - 7b the actual expansion. So 5b might ne needed for the efficiency.
 
Is it possible that the points 5b and 7b refer to another problem?
 

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