Thermodynamics HW Solutions 246

# Thermodynamics HW Solutions 246 - Chapter 3 Steady Heat...

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Chapter 3 Steady Heat Conduction 3-128 Hot water is flowing through a pipe that extends 2 m in the ambient air and continues in the ground before it enters the next building. The surface of the ground is covered with snow at 0 ° C. The total rate of heat loss from the hot water and the temperature drop of the hot water in the pipe are 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 ground is constant. 4 The pipe is at the same temperature as the hot water. Properties The thermal conductivity of the ground is given to be k = 1.5 W/m °C. Analysis ( a ) We assume that the surface temperature of the tube is equal to the temperature of the water. Then the heat loss from the part of the tube that is on the ground is W 498 C ) 8 80 )( m 3142 . 0 )( C . W/m 22 ( ) ( m 3142 . 0 ) m 2 )( m 05 . 0 ( 2 2 2 = ° ° = = = = = T T hA Q DL A s s s & ππ 8 ° C 3 m 80 ° C 0 ° C 20 m Considering the shape factor, the heat loss for vertical part of the tube can be determined from m 44 . 3 )
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## This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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