9-101 9-134 A regenerative gas-turbine cycle with three stages of compression and three stages of expansion is considered. The thermal efficiency of the cycle is to be determined. Assumptions 1 The air standard assumptions are applicable. 2 Air is an ideal gas with constant specific heats at room temperature. 3 Kinetic and potential energy changes are negligible. Properties The properties of air at room temperature are cp = 1.005 kJ/kgK and k = 1.4 (Table A-2a). Analysis The temperatures at various states are obtained as follows T2 T4 T6 T1 r p( k 1) / k (290 K)(4) 0.4/1.4 430.9 K T T7 T6 20 430.9 20 450.9 K q in c p (T8 T7 ) q in T8 T7 cp 1 T9 T8 rp T10 T9 cp 1 T11 T10 rp T12 T11 T13 q in cp 1 T12 rp 450.9 K ( k 1) / k q in 9 7 300 kJ/kg 749.4 K 1.005 kJ/kg K 6 290 K 1 (749.4 K) 4 504.3 K ( k 1) / k 504.3 K 5 2 3 1 13 11 14 s 300 kJ/kg 802.8 K 1.005 kJ/kg K 1 (802.8 K) 4 540.2 K ( k 1) / k 0.4/1.4 4 12 1 8 0.4/1.4 540.2 K 300 kJ/kg 838.7 K 1.005 kJ/kg K 1 (838.7 K) 4 0.4/1.4 564.4 K T14 T13 20 564.4 20 544.4 K The heat input is q in 300 300 300 900 kJ/kg The heat rejected is q out c p (T14 T1 ) c p (T2 T3 ) c p (T4 T5 ) (1.005 kJ/kg K)(544.4 290 430.9 290 430.9 290) R 538.9 kJ/kg The thermal efficiency of the cycle is then th 1 q out 538.9 1 0.401 40.1% 900 q in PROPRIETARY MATERIAL. © 2011 The McGraw-Hill Companies, Inc. Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission.

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