Liquid nitrogen is stored in a thin-walled metallic sphere of radius rl = 0.25 m. The sphere is covered with an insulating material of thickness 25 mm and U = 0.068 W/(m 2 K). The exposed surface of...

Liquid nitrogen is stored in a thin-walled metallic sphere of radius rl = 0.25 m. The sphere is covered with an insulating material of thickness 25 mm and U = 0.068 W/(m²
K). The exposed surface of the insulation is surrounded by air at 300 K. The convective heat transfer coefficient to the air is U = 20 W/(m²K). The latent heat of vaporization and density of liquid nitrogen are 200 kJ/kg and 804 kg/m3, respectively. Liquid nitrogen boils at 77 K at 1 atm. What is the rate of liquid boil-off in kilograms per day?