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19brayton_irrev

19brayton_irrev - Regeneration Brayton cycle irreversible...

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Regeneration Brayton cycle - irreversible An actual gas turbine differs from the ideal due to inefficiencies in the turbines and compressors and pressure losses in the flow passages (heat exchangers in closed cycle). The T - s diagram may be as shown: static data for plot T-s diagram temperature 1200 1000 800 600 400 1 1.2 1.4 1.6 entropy reversible cycle irreversible cycle regeneration inlet temperature reversible irreversible, heat exchanger maximum regeneration inlet temperature irreversible T 2s 2 3 4 1 6 7s 7 5s 5 s 7ss 8 1.8 2 2.2 state - reversible process 1 - start 2s - reversible compressor outlet 3 - outlet of heat addition T 3 = T max 4 - outlet of turbine 5s - inlet to regenerator T 5s = T 4 irreversible 1 - start 2 - irreversible compressor outlet 6 - outlet of heat addition T 6 = T max 4 - outlet of turbine 5 - inlet to regenerator T 5 = T 7 11/21/2005 1

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irreversible processes can be described by some efficiencies and heat transfer effectiveness: N.B. the efficiencies are defined wrt irreversible overall cycle h 6 h 7 T 6 T 7 turbine efficiency η t = h 6 h 7s = T 6 T 7s η t := 0.8 compressor efficiency η c = h 2s h 1 = T 2s T 1 η c := 0.78 h 2 h 1 T 2 T 1 T 5 T 2 heat exchanger effectiveness ε = ε := 94% T 7ss T 2 δ p H pressure loss in heater p 6 = p 3 − δ p H = p 3 1 delta_p_over_p_H := 5% p 3 δ p L pressure loss (increase) p 7 = p 1 + δ p L = p 1 1 + delta_p_over_p_L := 3% in cooler, relative to p 1 p 1 we will combine these as follows as for efficiency only
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19brayton_irrev - Regeneration Brayton cycle irreversible...

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