GATE Mechanical 2014 Set 2 | Question: 42

Question

A hemispherical furnace of $1$ m radius has the inner surface (emissivity, $\varepsilon =1$) of its roof maintained at $800$ $K$, while its floor ($\varepsilon  =5.0$) is kept at $600 K$. Stefan-Boltzmann constant is $5.668 \times 10^−8$ $W / m^2$.$K^4$. The net radiative heat transfer (in $kW$) from the roof to the floor is _______