Thermodynamics HW Solutions 245

Thermodynamics HW Solutions 245 - Chapter 3 Steady Heat...

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Chapter 3 Steady Heat Conduction 3-126E A row of used uranium fuel rods are buried in the ground parallel to each other. The rate of heat transfer from the fuel rods to the atmosphere through the soil is to be determined. Assumptions 1 Steady operating conditions exist. 2 Heat transfer is two-dimensional (no change in the axial direction). 3 Thermal conductivity of the soil is constant. Properties The thermal conductivity of the soil is given to be k = 0.6 Btu/h ft °F. Analysis The shape factor for this configuration is given in Table 3-5 to be 5298 . 0 ) ft 12 / 8 ( ) ft 15 ( 2 sinh ) ft 12 / 1 ( ) ft 12 / 8 ( 2 ln ) ft 3 ( 2 4 2 sinh 2 ln 2 4 total = π π π × = π π π × = w z D w L S Then the steady rate of heat transfer from the fuel rods becomes T 2 = 60 ° F 8 in T 1 = 350 ° F 15 ft D = 1 in L = 3 ft Btu/h 92.2 = ° ° = = C ) 60 350 )( F Btu/h.ft. 6 . 0 )( ft 5298 . 0 ( ) ( 2 1 total T T k S Q & 3-127 Hot water flows through a 5-m long section of a thin walled hot water pipe that passes through the center of a 14-cm thick wall filled with fiberglass insulation.
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