Chemical Engineering - Heat Transfer - Discussion

Discussion Forum : Heat Transfer - Section 3 (Q.No. 43)
43.
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
0.35
0.45
0.55
0.85
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
11 comments Page 1 of 2.

Zahraa said:   3 years ago
I think it's wrong in question because the incident radiant energy must be more than the reflected energy so it must be 1000 kcal/s not 100 kcal/s.
(1)

VINOD said:   7 years ago
Very good, Thanks @Monika.

Nik said:   7 years ago
Thanks @Monika.

Shriraj said:   7 years ago
Thanks @Monica.

Ritesh said:   7 years ago
Thanks @Monika.

Monika said:   7 years ago
A+t+r=1.
R=300/1000=0.3,
t=0.25,
A=1-0.55=0.45,
Emmisivity=A of sample/A of black.
O.45/1=0.45.
(5)

Swathi said:   8 years ago
Please explain it briefly.
(1)

Philip said:   8 years ago
@Nizam Ali.

Thats true, or maybe the incident energy should be 1000 kcal/s.

Danish said:   8 years ago
How? explain me.

Nizam ali said:   8 years ago
I think it should be 30kcal/sec not 300kcal/sec.


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