Q135
Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be
A.
One
B.
Two
C.
Three
AnswerD.
Four
Answer: Option C
Solution
Answer: Option C
Solution:
N = number of parallel shields
0.25n + 0.25 = 1
0.25n = 0.75
n = 3.