Given: Two$-$phase liquid oxygen is stored in a spherical tank that is $1$ m in diameter. The tank is enclosed by another tank that is $1\mathrm{.}5$ m in diameter $($concentric with inner tank$)$ and its surface is maintained at $273$ K $.$ The region between the two tanks is maintained at a vacuum. The goal is to reduce the heat gain to the liquid oxygen. It is expensive to treat the tank surfaces with low e coatings and calculations will be made to determine which surface to coat.

Find: Calculate the rate of heat loss between the tank walls first assuming the outer surface of the inner tank has ${}_1=0\mathrm{.}01$ and the inner surface of the outer tank has ${}_0=0\mathrm{.}8$ and then switch the emissivity value. Recommend which surface should be coated with the low emissivity coating.

Assume: $1.$ The oxygen is at a pressure of $1$ atm $.2.$ The inner tank wall is at the saturation temperature for two phase oxygen.