Helium in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under air standard conditions, the thermal efficiency of this cycle is
A)20.5%
B)84.3%
C)79.5%
D)61.4%
E)67.4%

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
V1=4 "L"
V2= 0.25 "L"
V3= 0.50 "L"
r=V1/V2
rc=V3/V2
k=1.667
Eta_Diesel=1-(1/r^(k-1))*(rc^k-1)/k/(rc-1)
"Some Wrong Solutions with Common Mistakes:"
W1_Eta = 1-(1/r1^(k-1))*(rc^k-1)/k/(rc-1); r1=V1/V3 "Wrong r value"
W2_Eta = 1-Eta_Diesel "Using incorrect relation"
W3_Eta = 1-(1/r^(k1-1))*(rc^k1-1)/k1/(rc-1); k1=1.4 "Using wrong k value"
W4_Eta = 1-1/r^(k-1) "Using Otto cycle efficiency"

Helium in an Ideal Diesel Cycle Is Compressed from 4