Estimation of heat flow through a composite wall with constant thermal conductivities

Example 2.4 Estimation of heat flow through a composite wall with constant thermal conductivities A pipe with an outside diameter of 10 cm and a length of 110 m is carrying hot fluid. The pipe is insulated with 0.5 cm thick silica foam and 10 cm thick fiberglass. The pipe wall is at 120°C and the outside surface of the fiberglass is at 30°C. Estimate the heat flow in the radial direction of the pipe. The thermal conductivities of silica foam and fiberglass are 0.055 and 0.0485 W/(m K), respectively. 

Assume radial heat flow only, and the thermal conductivities of the insulation layers are constant. 

For heat flow in the radial direction of a pipe only, Eq. (2.26) is 

Another example of one-dimensional heat flow is the radial heat flow through the wall of a hollow sphere. Starting withEq. (2.36) 

By integrating this equation with the boundary conditions  

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Example 2.4 Estimation of heat flow through a composite wall with constant thermal conductivities A pipe... 

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