Air at 900 kPa and 25°C is allowed to expand steadily and isothermally to 100 kPa at a rate of 1.4 kg/s. The maximum power output of the turbine is
A)22 kW
B)188 kW
C)263 kW
D)137 kW
E)94 kW

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
Cp=1.005 "kJ/kg.K"
R=0.287 "kJ/kg.K"
Cv=0.718 "kJ/kg.K"
k=1.4
P1=900 "kPa"
T=25 "C"
m=1.4 "kg/s"
P2=100 "kPa"
Wout=m*R*(T+273)*ln(P1/P2)
"Some Wrong Solutions with Common Mistakes:"
W1_Wout=m*R*T*ln(P1/P2) "Using C instead of K"
W2_Wout=m*T*(P1-P2) "Using wrong relation"
W3_Wout=R*(T+273)*ln(P1/P2) "Not using mass flow rate"

Air at 900 KPa and 25°C Is Allowed to Expand