Question

Problem 7: (15 pts) An ideal air-standard Brayton cycle operates steadily with pressure limits of the cycle are 100 kPa and 800 kPa. The temperature at the exit of turbine is 500 K. During the heat rejection process, heat is released from the cycle at a rate of 320 kW and the mass flow rate is 2 kg/s. The air is treated as an ideal gas with constant specific heats, i.e. k = 1.4 and R = 0.287 kJ/(kg · K). Tasks: (a) Determine the entropy change per unit mass (As) during the heat rejection process in kJ/kg . K (5 pts) (b) Determine the head addition rate (lin) during this cycle (5 pts) (C) Determine the back work ratio (5 pts)

Answer 1

Is diagram! TA 3 gada >Wp po 2500k 80okla 4 PzP4 2100 kPa Pzzlz = 800 kPa Tyas grejection Mass flow rotte ()= 2 kylkec. K=l4 and R = 0.284 kilugik. 320 KW We grejection lookPa Ag

hy =503.02 160320 kJ sec sec Enthalpy of air at 500k, RJ/kg eat rejection zů (hy-hi) 2kg (503-02-hi) hi = 343.02 kg lng Also, h, z Cp. I T Change fu entropy per unit mass, (AS) z Co. en 14 h 2 343.02 K K = 341.31 k. 1.005 P -Bilme po T4 cro. 383 = 1.005.lu 341.31 ках, к 500

( 6 ) K-YK 1.4-Y4 1 / 2 6180265 K. ² * T3 905-12 k. T. * 1 2 341.31x/8001 100 12 Z₂ x tu 618.265 x 500 14 T 341.31 feat addition rate (Qin) z on Cp (P3-P2) 22x1,005. x (905.72 618,265) KW = 577.19 kW Compressor Work Wiz mCp (2-1) Turbfue Work, Wiz am Cp (13-14) Back Work Ratjo (BWR) unich (22-to) 618.265-341.31 nice (1.3-tu) Z 905.72 - 500 ling 0 68