A pipeline, used for the4.20 WP transport of crude oil, is buried in the earth such that its center line is a distance of 1.5 m below the surface. The pipe has an outer diameter of o.5 m and is insulated with a layer of cellular glass 100 mm thick. What is the rate of heat loss per unit length of pipe when heated oil at 120°C flows through the pipe and the surface of the earth is at a temperature of o°C?

Fig: 1