Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion

Discussion Forum : Heat Transfer, Refrigeration and Air Conditioning - Section 3 (Q.No. 5)
5.
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
one
two
three
four
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
9 comments Page 1 of 1.

Dushmant said:   5 years ago
You are Correct @Pradeep.

It is 3 when all emissivity will be same.

Pradeep said:   7 years ago
Emissivity should be same for shield also. Then the given answer is correct.

Emmanuvelbibin said:   7 years ago
Yes, you are correct @Bharat.

BAVAN BHARAI said:   7 years ago
Thnks for all your explanation guidance. It is very useful
(1)

Heisenberg said:   8 years ago
Thanks a lot @Amal! Your explanation useful to me.

AMAL said:   8 years ago
0.25n+0.25 = 1.
0.25n = 0.75.
n = 3.

Bharat said:   9 years ago
Emissivity should be given 0.7 to get specified answer and to use Gaurav's formula.

Arun said:   9 years ago
Little confusion evaporator observe sensible heat or latent heat.

Gaurav said:   10 years ago
Q with shield/Q without shield = 1/n+1.

N = no.of parallel shields.

Post your comments here:

Your comments will be displayed after verification.