For given combined radioactive and convective heat transfer coefficient 'h_t' and given thermal conductivity k. Critical thickness of insulation for cylinder and sphere is given as
- A. k/h_t and k/h_t^2
- B. k/h_t and 2k/h_t
- C. 2k/h_t and k/2h_t
- D. k/h_t and k/h_t
Answer: B. k/h_t and 2k/h_t
Explanation: Critical radius for cylinder = k/h. Critical radius for sphere = 2k/h. Thickness refers to radius here.