State and explain Lambert law. How is it used in radiative heat transfer calculation? For a diffused flat surface having Emissivity of 0.7 at a temperature of 800°C, calculate normal intensity of radiation.
(i) What would be the intensity of radiation at an angle of 30° with respect to normal direction?
(ii) For a very long semicircular duct having surface areas A2 and A1 as shown below:
Determine shape factors F12 , F21 , F22