Thermodynamics HW Solutions 210

Thermodynamics HW - Chapter 15 Steady Heat Conduction 3-75E A steam pipe covered with 2-in thick fiberglass insulation is subjected to convection

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Chapter 15 Steady Heat Conduction 3-75E A steam pipe covered with 2-in thick fiberglass insulation is subjected to convection on its surfaces. The rate of heat loss from the steam per unit length and the error involved in neglecting the thermal resistance of the steel pipe in calculations are to be determined. Assumptions 1 Heat transfer is steady since there is no indication of any change with time. 2 Heat transfer is one-dimensional since there is thermal symmetry about the center line and no variation in the axial direction. 3 Thermal conductivities are constant. 4 The thermal contact resistance at the interface is negligible. Properties The thermal conductivities are given to be k = 8.7 Btu/h ft °F for steel and k = 0.020 Btu/h ft °F for fiberglass insulation. Analysis The inner and outer surface areas of the insulated pipe are AD L L ii oo == = = ππ (./ ( . (8 / ( . 35 12 1 0 916 12 1 2 094 ft) ft) ft ft 2 2 R i T 1 R insulation R o T 2 R pipe The individual resistances are F/Btu h 65 . 5 096 . 0 516 . 5 002 . 0 036 . 0 F/Btu h 096 . 0 ) ft 094 . 2 ( F) . Btu/h.ft 5 ( 1 1 F/Btu h 516
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This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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