Air is to be compressed steadily and isentropically from 2 atm to 18 atm by a two-stage compressor. To minimize the total compression work, the intermediate pressure between the two stages must be
A)4 atm
B)12 atm
C)10 atm
D)6 atm
E)18 atm

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
P1=2 "atm"
P2=18 "atm"
P_mid=SQRT(P1*P2)
"Some Wrong Solutions with Common Mistakes:"
W1_P=(P1+P2)/2 "Using average pressure"
W2_P=P1*P2/2 "Half of product"

Air Is to Be Compressed Steadily and Isentropically from 2