PROBLEM 4.13 KNOWN:Surface temperatures of two parallel pipe lines buried in soil. FIND:Heat transfer per unit length between the pipe lines. SCHEMATIC:ASSUMPTIONS:(1) Steady-state conditions, (2) Two-dimensional conduction, (3) Constant properties, (4) Pipe lines are buried very deeply, approximating burial in an infinite medium, (5) Pipe length >> D1or D2and w > D1or D2. ANALYSIS:The heat transfer rate per unit length from the hot pipe to the cool pipe is ()12qSqkTLL′==−T.The shape factor S for this configuration is given in Table 4.1 as 222-12LS.4wDDcosh2D D
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