q2 Use constant specific heats at room temperature. Round all answers to one dec
ID: 1858637 • Letter: Q
Question
q2
Use constant specific heats at room temperature. Round all answers to one decimal place. A simple Brayton cycle operates with air with minimum and maximum temperatures of 27 degree C and 727 degree C. It is designed so that the maximum cycle pressure is 2,000 kPa and the minimum cycle pressure is 100 kPa; the isentropic efficiency of the turbine is 86.4 percent. Determine the net work produced per unit mass of air each time this cycle is executed and the cycle's thermal efficiency. w net = kJ/kg eta th = %Explanation / Answer
T1=300K
T3=1000K
P1=100Kpa
P2=2000Kpa
eff turbine=86.4%
T2/T1=(P2/P1)^(k-1)/k=T3/T4
T2=706.064K
T4=424.89 K
Qs=m*cp(T3-T2)=1.005(1000-706.064)=295.11 Kj/Kg
Qr=m*cp*(T4-T1)=125.38 Kj/Kg
Wnet= Qs-Qr=295.11-125.38=169.72Kj/Kg
Eff=Wnet/Qs=169.72/295.11=0.5757.5%
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