Negative Exergy destruction values – Asimptote

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This topic has 3 replies, 2 voices, and was last updated 2 years, 5 months ago by Teus van der Stelt.

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- July 5, 2022 at 6:24 am #1771
  
  sreekanth.manavalla
  Participant
  
  I sometimes find that for a Sink/Source, which is a source of a fluid, the exergy loss (exergy destroyed) is negative. Is it because there is no inlet stream of fluid into the Sink/Source?
- July 5, 2022 at 10:07 am #1772
  
  Teus van der Stelt
  Keymaster
  
  Dear Sreekanth, if could upload a specific, simple, example of such a case, that would be helpful.
  - July 5, 2022 at 11:01 am #1773
    
    sreekanth.manavalla
    Participant
    
    In the attachment, sink/sources 2, 3 and 7 have negative exergy losses. Does it imply exergy generation?
- July 18, 2022 at 9:33 am #1816
  
  Teus van der Stelt
  Keymaster
  
  If you make the air composition exactly like the Baehr environment conditions (it differs from the standard air composition and p = 1.01325 bar in your case) then you can see that the exergy flow in source 1 is only 0.01 kW, which may be a round-off error, as it should be 0 kW. In sink/source 2 the temperature is increased by 5 K. As a consequence the exergy flow to the system is 0.04 kW.
  
  In source 7 the pressure and temperature of the flue gasses are 2 bar and 250 C and the composition differs from the environment composition, which introduces both a thermo-mechanic and chemical exergy flow to the system.
  
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