The net radiant interchange between two parallel oxidised iron plates is $2900W.$

Example $4\mathrm{.}9$: Calculate the rate of heat loss from a thermoflask if the polished silvered surfaces have emissivities of $0\mathrm{.}05,$ the liquid in the flask is at $368K(95C)$ and the casing is at $293K(20C).$ Calculate the loss if both surfaces were black.

Stefan Boltzmann constant $=5\mathrm{.}67{10}^{-8}\frac{W}{m^2*K^4}$