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THERMODYNAMICS - CASE STUDY

    Introduction


Improving a Power Plant
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Andrew's company bought an old power plant which is running a simple Brayton cycle without regeneration for years. Modifications are needed to increase the power generation and thermal efficiency. Several suggestions are given. Andrew is given the task to compare all the plans.

What is known:

  • The conditions for the simple Brayton cycle:

    Compression ratio: 8
    Compressor inlet pressure: 100 kPa
    Minimum temperature: 300 K
    Maximum temperature: 1300 K
  • Plan 1: Use regeneration. The effectiveness of the regenerator is 0.8
  • Plan 2: Two-stage intercooling, reheating, and regeneration with the same temperature limit and compression ratio.
     
    Question


 

Determine which plan has the highest power output, which one has the highest thermal efficiency under the same temperature limits and compression ratio.

     
    Approach


 
  • Determine temperature and pressure in each state of the cycle.
  • The thermal efficiency can be determined by its general definition:
    ηth = 1 - qout /qin