PROBLEM 4.16 KNOWN:Thin-walled copper tube enclosed by an eccentric cylindrical shell; intervening space illed with insulation. fFIND:Heat loss per unit length of tube; compare result with that of a concentric tube-shell rrangement. aSCHEMATIC:ASSUMPTIONS:(1) Steady-state conditions, (2) Constant properties, (3) Thermal resistances of opper tube wall and outer shell wall are negligible, (4) Two-dimensional conduction in insulation. cANALYSIS:The heat loss per unit length written in terms of the shape factor S is and from Table 4.1 for this geometry, ()(12qkS/TT′=−A)222-1SDd2/cosh.2Ddπ⎡⎤+−=⎢⎥⎣⎦A4zSubstituting numerical values, all dimensions in mm, 2-1-1120304 20S2 / cosh2 / cosh1.9034.991.
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