Chapter 3, Problem 90P

Exposure to high concentrations of gaseous ammonia can cause lung damage. To prevent gaseous ammonia from leaking out, ammonia is transported in its liquid state page 232 through a pipe $(k=25\text{ W/m}\text{.K,}\text{}{\text{ D}}_{\text{i}}{\text{ =25 cm, D}}_{\text{o}}\text{=4 cm and L= 10 m)}\text{.}$ and 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 anunonia and the ambient air are 100 Wm2K and 20 Vin2K. respectively. Determine the insulation thickness for the pipe using a material with $\text{k = 0}{\text{.75W/m}}^{\text{2}}\text{.K,}$ to keep the liquid ammonia flowing at an average temperature of -35°C, while maintaining the insulated pipe outer surface temperature at 10°C.