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
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