Thermodynamics HW Solutions 288

Thermodynamics HW Solutions 288 - ⋅ °C ğ Analysis The...

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Chapter 3 Steady Heat Conduction 3-176 A spherical tank containing iced water is buried underground. The rate of heat transfer to the tank is to be determined for the insulated and uninsulated ground surface cases. Assumptions 1 Steady operating conditions exist. 2 Heat transfer is two-dimensional (no change in the axial direction). 3 Thermal conductivity of the concrete is constant. 4 The tank surface is assumed to be at the same temperature as the iced water because of negligible resistance through the steel. Properties The thermal conductivity of the concrete is given to be k = 0.55 W/m
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Unformatted text preview: ⋅ °C. ğ Analysis The shape factor for this configuration is given in Table 3-5 to be m 30 . 10 m 4 . 2 m 4 . 1 25 . 1 ) m 4 . 1 ( 2 25 . 1 2 = − π = − π = z D D S Then the steady rate of heat transfer from the tank becomes W 102 = ° − ° = − = C ) 18 )( C W/m. 55 . )( m 30 . 10 ( ) ( 2 1 T T Sk Q & T 1 =18 ° C T 2 = 0 ° C z = 2.4 m D = 1.4 m If the ground surface is insulated, m 68 . 7 m 4 . 2 m 4 . 1 25 . 1 ) m 4 . 1 ( 2 25 . 1 2 = + π = + π = z D D S W 76 = ° − ° = − = C ) 18 )( C W/m. 55 . )( m 68 . 7 ( ) ( 2 1 T T Sk Q & 3-131...
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