Problem 10-2 - Example 10-2 Air flowing at 150 lbm/min...

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Example 10-2 Air flowing at 150 lbm/min enters the compressor of a Brayton cycle. The air enters at 70°F, 14.7 psia and is compressed to 120 psia. It is heated to 2272 R and fed into the turbine. If the isentropic efficiency of the compressor is 0.86 and that of the turbine is 0.9, a) Calculate net work b) Calculate cycle efficiency c) Draw a T-s diagram Use EES to evaluate properties (variable specific heats) Solution: Begin the analysis with the compressor 1 Btu entropy(Air, 70 460, 14.7) 1.36 lbm R sT P == + = = 21 s s s = () 12 s ideal s C act mh h Wh h Wm h h h h η = −− ± ± ± ± 22 Btu enthalpy(Air, 120, ) 231 lbm ss hP s s = = 1 s C hh h h =− 1 Btu enthalpy(Air, 70 460, 14.7) 126.8 lbm hT P + = = 2 Btu 1 Btu 126.8 126.8 231.1 lbm 0.86 lbm h
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2 Btu 248.1 lbm h = () 21 C Wm h h =− ± ± lbm Btu Btu 150 248.1 126.8 18,197 min lbm min C W = ± For the turbine 3 Btu entropy(Air, 2272, 120) 1.584 lbm R sT P == = = 43 s s s = 34 act T ideal s s mh h Wh h h h h h η = −− ± ± ± ± 44 Btu enthalpy(Air, 14.7, ) 326.1 lbm ss hP s s = = Ts hh h h 3 Btu enthalpy(Air, 2272) 580.8 lbm hT = 4 Btu Btu 580.8 0.9 580.8 326.1 lbm lbm h 4 Btu 351.6 lbm h = T h h ± ± lbm Btu
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Problem 10-2 - Example 10-2 Air flowing at 150 lbm/min...

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