Two long pipes, one having a 10-cm-OD and a surface temperature of 300°C, the other having a 5-cm-OD and a surface temperature of 100°C, are buried deeply in dry sand with their centerlines 15 cm apart. Determine the rate of heat flow from the larger to the smaller pipe per meter length.

GIVEN

Two long pipes buried deeply in dry sand

Pipe 1

Diameter (D1) = 10 cm = 0.1 m,

Surface temperature (T1) = 300°C

Pipe 2

Diameter (D2) = 5 cm = 0.05 m,

Surface temperature (T2) = 100°C

Spacing between their centerlines (s) = 15 cm = 0.15 m

FIND

The rate of heat flow per meter length (q/L)

ASSUMPTIONS

The heat flow between the pipes is two dimensional

The system has reached steady state

The thermal conductivity of the sand is uniform

SKETCH


The shape factor for this geometry, is



The rate of heat transfer per unit length is

Physics & Space Science

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