In an ideal Brayton cycle with regeneration, air is compressed from 80 kPa and 10°C to 400 kPa and 180°C, is heated to 450°C in the regenerator, and then further heated to 1200°C before entering the turbine. Under cold air standard conditions, the effectiveness of the regenerator is
A)26%
B)42%
C)65%
D)57%
E)89%

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
k=1.4
Cp=1.005 "kJ/kg.K"
P1=80 "kPa"
P2=400 "kPa"
T1=10+273 "K"
T2=180+273 "K"
T3=1200+273 "K"
T5=450+273 "K"
"The highest temperature that the gas can be heated in the regenerator is the turbine exit temperature,"
rp=P2/P1
T2check=T1*rp^((k-1)/k) "Checking the given value of T2. It checks."
T4=T3/rp^((k-1)/k)
Effective=(T5-T2)/(T4-T2)
"Some Wrong Solutions with Common Mistakes:"
W1_eff = (T5-T2)/(T3-T2) "Using wrong relation"
W2_eff = (T5-T2)/(T44-T2); T44=(T3-273)/rp^((k-1)/k) "Using C instead of K for T3"
W3_eff = (T5-T2)/(T444-T2); T444=T3/rp "Using wrong relation for T4"

In an Ideal Brayton Cycle with Regeneration, Air Is Compressed