• # question_answer Gas turbine develops 120 kJ of work while the compressor absorbed 60 kJ of work and the heat supplied is 200 kJ. If regenerator which would recover  40% of the heat in the exhaust were used, then the increase in the overall thermal efficiency would be: A) 10.2%              B) 8.6%C) 6.9%                D) 5.7%

Solution :

${{y}_{th}}\frac{{{W}_{t}}-{{W}_{c}}}{{{Q}_{s}}}=\frac{120-60}{200}=\frac{60}{200}=0.3\,\,or\,\,30%$Heat in exhaust gases $={{Q}_{s}}-{{W}_{t}}=200-120=80\,kJ$ Heat recovered in regenerator $=0.4\times 30=32\,kJ$. Heat supplied $=200-32-168\,\,kJ$ New efficiency $=\frac{200-60}{168}=35.7%$ Increase in efficiency $=-35.7-30.0=5.7$

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