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GATE 2019 ME (ME2) – Question 20

Heat Transfer · Radiative heat transfer: laws, view factors, radiation network · 1 mark · Multiple choice

Sphere 1 of diameter 0.1 m is completely enclosed by sphere 2 of diameter 0.4 m. Find view factor $F_{12}$.

  1. 0.0625
  2. 0.25
  3. 0.5
  4. 1.0

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Correct answer: (D) 1.0

Explanation

The inner sphere is convex, so $F_{11}=0$. All radiation leaving it reaches the enclosing sphere. Summation gives **$F_{12}=1$, D**. The area ratio applies to the reverse view factor.