Question

A metal storage tank of external area 0.5 m^2 contains water at 65 degree C. & is located inside a large enclosure with wall at 10 deg.C. the tank is painted black on the outside & its emissivity is approx. to 0.95. How much reduction in heat loss would occur if the outside surface was coated with aluminium paint of emissivity 0.55? Take radiation constant qb = 6.86*10^-8 kcal/m^2-hr-k^4