Chapter 3, Problem 89P

Liquid hydrogen is flowing through an insulated pipe $(k=23\text{ W/m}\text{.K,}\text{}{\text{ D}}_{\text{i}}{\text{ =3 cm, D}}_{\text{o}}\text{=4 cm and L= 20 m)}$. The pipe is situated in a chemical plant, where the average air temperature is 40°C. The convection heat transfer coefficients of the liquid hydrogen and the ambient air are 200 W/m² K and 50 W/m² .K, respectively. If the oilier surface temperature of the insulated pipe is 5°C, determine the thickness of the pipe insulation $(k=0.6\text{ W/m}\text{.K)}$ and in order to keep the liquid hydrogen flowing at an average temperature of -300°C.