For given combined radiative and convective heat transfer coefficient ‘ht’ and given thermal conductivity k, Critical thickness of insulation for cylinder and sphere is given as

\(\frac{{2k}}{{{h_t}}}\) and \(\frac{k}{{h_t^2}}\)

\(\frac{k}{{{h_t}}}\) and \(\frac{k}{{h_t^2}}\)

\(\frac{k}{{{h_t}}}\) and \(\frac{{2k}}{{{h_t}}}\)

\(\frac{{2k}}{{{h_t}}}\) and \(\frac{k}{{{h_t}}}\)

For given combined radiative and convective heat transfer coefficient

1.	For given combined radiative and convective heat transfer coefficient ‘ht’ and given thermal conductivity k, Critical thickness of insulation for cylinder and sphere is given as
A.	\(\frac{k}{{{h_t}}}\) and \(\frac{k}{{h_t^2}}\)
B.	\(\frac{k}{{{h_t}}}\) and \(\frac{{2k}}{{{h_t}}}\)
C.	\(\frac{{2k}}{{{h_t}}}\) and \(\frac{k}{{h_t^2}}\)
D.	\(\frac{{2k}}{{{h_t}}}\) and \(\frac{k}{{{h_t}}}\)
Answer» C. \(\frac{{2k}}{{{h_t}}}\) and \(\frac{k}{{h_t^2}}\)

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For given combined radiative and convective heat transfer coefficient ‘ht’ and given thermal conductivity k, Critical thickness of insulation for cylinder and sphere is given as

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