Problem 3 (30 points): A thin cylindrical tube having a diameter of 1.2m and a length of 1m is filled with liquid nitrogen at -100C. Insulation with a thermal conductivity 0.05 W/m.K. and thickness 250mm is applied to the tube from the outside to reduce the heat gain. Assuming that the tube's outside surface temperature is that of the liquid nitrogen, the ambient air is at a temperature of 25C, and the convection heat transfer coefficient on the outer surface of the insulation is 7 W/m.K.: 1. Calculate the overall heat transfer coefficient. 2. Calculate the heat transfer rate to the liquid nitrogen. 3. Determine the radial position in the insulating layer at which the temperature is -20C