1. (35 pts.) A 1-m internal diameter and 2 m length cylindrical tank is made of 20 mm thick stainless steel (k = 15W/m K). The tank is used to store liquid nitrogen at 77K. Tank is insulated with an insulation material which have a thermal condictivity k 0.015 W/m K and the outer radius of the insulation is equal to 2000 times of critical radius of insulation. Temperature of the outer surface of the tank was measured as 299K and it is exposed to ambient air of 300K The outer surface of the tank is painted white and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection coefficient is known to be 20 W/m2 K. The latent heat of vaporization and the density of liquid nitrogen are 2x10' J/kg and 804 kg/m', respectively. a. What is the rate of heat transfer to the liquid nitrogen? b. What is the rate of liquid boil-off (L/day)? Hint: 1. Neglect the resistance to heat transfer from the container wall to the liquid nitrogen. 2. Use combined heat transfer coefficient to calculate critical radius of insulation. Vent mhrg Air T=300 K air Insulation Liquid nitrogen Stainless steek