Total emissivity of polished silver compared to black body is___________________?

Question: A __________ surface has the maximum thermal emissivity out of the following.
[A].

black & smooth

[B].

black & rough

[C].

white & smooth

[D].

white & rough

Answer: Option B

Explanation:

No answer description available for this question.

Question: jH factor for heat transfer is not a function of the __________ number.
[A].

Reynolds

[B].

Nusselt

[C].

Grashoff

[D].

both (b) & (c)

Answer: Option D

Explanation:

No answer description available for this question.

Question: A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
[A].

5 minutes

[B].

10 minutes

[C].

20 minutes

[D].

40 minutes

Answer: Option A

Explanation:

No answer description available for this question.