A spherical tank of 3-m diameter contains a liquefied petroleum gas at -60°C. Insulation with a thermal conductivity of 0.06 W/m. K and thickness 250 mm is applied to the tank to reduce the heat gain.

(a) Determine the radial position in the insulation layer at which the temperature is O°C when the ambient air temperature is 20°C and the convection coefficient on the outer surface is 6 W/m2 ∙ K.

(b) If the insulation is pervious to moisture from the atmospheric air, what conclusions can you reach about the formation of ice in the insulation? What effect will ice formation have on heat gain to the LP gas? How could this situation be avoided?