1. INCCA UNIVERSITY FACULTY OF COLOMBIA
engineering, administration and basic science Mechanical Engineering
Fabio Ernesto Ballén Gómez
66365
Thermal Plants
EXAMPLE E8-3 A stationary power plant operating on a simple Brayton cycle has a pressure
ratio of 10. The compressor efficiency is 80% and its inlet conditions are 100 kPa and 300 K with a
3
flow rate of 10 m /s. The turbine efficiency is 85% and its inlet temperature is 1400 K. Using the air
standard Brayton cycle to model the power plant.
STATE P1 T1 Vel1 Z1 Voldot1 m1 [kg/s] h1[kJ/kg]
1 100kPa 300 K 0,0 m/s 0,0m 10m^3/s 11,615 1,85
STATE P2 s2 Vel2 Z2 mdot2 T2 [K] h2[kJ/kg]
2 =P1*10kPa =s1 0,0 m/s 0,0m =mdot1 579,6 282,4
STATE P3 h3 Vel3 Z3 mdot3 T3 [K] h3[kJ/kg]
3 =P2 =h1+(h2-h1)/0,8 0,0 m/s 0,0m =mdot1 649,5 352,5
STATE P4 T4 Vel4 Z4 mdot4 h4[kJ/kg] s4[kJ/kgK]
4 =P2 1400K 0,0 m/s 0,0m =mdot1 1105,7 7,77
STATE P5 s5 Vel5 Z5 mdot5 T5 [K] h5[kJ/kg]
5 =P1 =s4 0,0 m/s 0,0m =mdot1 724,6 428
STATE P6 h6 Vel6 Z6 mdot6 T6 [K] h6[kJ/kg]
6 =P1 =h4-((h4-h5)*0,85) 0,0 m/s 0,0m =mdot1 826 529,7
Data found by subrata Calculator
DEVICE PANEL
DEVICE IN – OUT W [kw] Q [kw] T_B
A 1-3 4073,22 0 25 [deg – C]
B 3-4 0 8747,86 1900 [K]
C 4-6 6690,62 0 25 [deg – C]
D 6-1 0 6130,46 20 [deg – C]

2. INCCA UNIVERSITY FACULTY OF COLOMBIA
engineering, administration and basic science Mechanical Engineering
Fabio Ernesto Ballén Gómez
66365
Thermal Plants
An energy analysis is carried out for each device now that the enthalpies at each principal state are
known:
state T [K] S [KJ/Kg K]
1 300 6,9
2 579,6 6,9
3 649,5 7
4 1400 7,77
5 724,6 7,77
6 826 7,9
Brayton cycle efficiency will:
Wnet = 6690,62 – 4073,22 = 2617,4 kW
ηb = Wnet / Qin = 2614,4 / 8747,86 = 29,9%