Exposure to high concentration of gaseous ammonia can cause lung damage. To prevent gaseous ammonia from leaking out, ammonia is transported in its liquid state through a pipe (k = 25 W/m ∙ K, D_i = 2.5 cm, D_o = 4 cm, and L = 10 m). Since liquid ammonia has a normal boiling point of −33.3°C, the pipe needs to be properly insulated to prevent the surrounding heat from causing the ammonia to boil. The pipe is situated in a laboratory, where the average ambient air temperature is 20°C. The convection heat transfer coefficients of the liquid hydrogen and the ambient air are 100 W/m² ∙ K and 20 W/m² ∙K, respectively. Determine the insulation thickness for the pipe using a material with k = 0.75 W/m ∙ K to keep the liquid ammonia flowing at an average temperature of 235°C, while maintaining the insulated pipe outer surface temperature at 10°C.