Question: A spherical tank (k = 15 W/m·K) with an inner diameter of 3 m and a wall thickness of 10 mm is used for storing hot liquid. The hot liquid inside the tank causes the inner surface temperature to be as high as 100°C. To prevent thermal burns on the skin of the people working near the vicinity of the tank, the tank is covered with a 7-cmthick layer of insulation (k = 0.15 W/m·K) and the outer surface is painted to give an emissivity of 0.35. The tank is located in a surrounding with air at 16°C. Determine whether or not the insulation layer is sufficient to keep the outer surface temperature below 45°C to prevent thermal burn hazards. Discuss ways to further decrease the outer surface temperature. Evaluate the air properties at 30°C and 1 atm pressure. Is this a good assumption?