A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is
A. 0
B. $$\frac{{{{\text{R}}_2}}}{{{{\text{R}}_1} + {{\text{R}}_2}}}$$
C. 1
D. $${\left( {\frac{{{{\text{R}}_1}}}{{{{\text{R}}_2}}}} \right)^2}$$
Answer: Option B
This Question Belongs to Chemical Engineering >> Heat Transfer
Correct answer is option D.
A1.F12=A2.F21 ....A1,A2 are area of first and second sphere respectively.
F21={A1/A2}*F12
Therefore,
F21={4πR1^2/4πR2^2}*F12
F21={R1/R2}^2*F12