GATE ME 2015 Set 3 — Question 50
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Heat Transfer → Radiation → View Factors
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Question
A solid sphere 1 of radius '' is placed inside a hollow, closed hemispherical surface 2 of radius ''. The shape factor is
Correct answer
(A) 1/12
Solution
Surface 1 is a sphere of radius . Area .
Surface 2 is a closed hemisphere of radius . Area .
.By reciprocity theorem: .
Since surface 1 is completely enclosed by surface 2, all radiation leaving 1 must strike 2, so .
.
Surface 2 is a closed hemisphere of radius . Area .
.By reciprocity theorem: .
Since surface 1 is completely enclosed by surface 2, all radiation leaving 1 must strike 2, so .
.
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