You must state clearly all the assumptions you make. All charts/tables referred

Question

You must state clearly all the assumptions you make.

All charts/tables referred to must be specified.

You must give clear description of the solution method (e.g. energy balance on the control volume, energy balance on the surface, application of Fouriers law etc.).

You must show all units.

Exxon is conducting heat loss analysis on its buried pipelines that are used to transport crude oil line in Alaska. The surface temperature of the earth there is 5 degree C. The pipe has an outer diameter of 15 cm and has a length of 4 m. It is buried in the earth at a depth of cm to its outer surface. The pipe wall temperature is to be maintained at 75 degree C Calculate the heat loss by the pipe assuming the thermal conductivity of the earth is 0.8 W/m K What is the heat loss if it is insulated with a layer of cellular glass 100 mm thick?

Explanation / Answer

1. a) heat loss by pipe = 0.8*(75 - 5)*15*0.3/0.2 = 1260 W

     b) heat loss when insulated = 0.8*(75 - 5)*15*0.3/0.3 = 840 W

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