Helium gas expands in an adiabatic turbine from 2 MPa and 750°C to 0.18 MPa at a rate of 1.5 kg/s. Assuming constant specific heats at room temperature, the maximum power output of the turbine is
A)1384 kW
B)830 kW
C)3613 kW
D)5316 kW
E)923 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=5.1926
k=1.667
P1=2000 "kPa"
T1=750 "C"
m=1.5 "kg/s"
P2=180 "kPa"
"s2=s1"
T2=(T1+750)*(P2/P1)^((k-1)/k)
W_max=m*Cp*(T1-T2)
"Some Wrong Solutions with Common Mistakes:"
Cv=3.1156 "kJ/kg.K"
W1_Wmax=m*Cv*(T1-T2) "Using Cv"
T22=T1*(P2/P1)^((k-1)/k) "Using C instead of K"
W2_Wmax=m*Cp*(T1-T22)
W3_Wmax=Cp*(T1-T2) "Not using mass flow rate"
T24=T1*(P2/P1) "Assuming T is proportional to P, using C"
W4_Wmax=m*Cp*(T1-T24)

Helium Gas Expands in an Adiabatic Turbine from 2 MPa