Thermodynamics HW Solutions 250

Thermodynamics HW Solutions 250 - 85 ° C L = 4 m D 32 ° C...

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Chapter 3 Steady Heat Conduction 3-133 Hot water passes through a row of 8 parallel pipes placed vertically in the middle of a concrete wall whose surfaces are exposed to a medium at 20 ° with a heat transfer coefficient of 8 W/m C 2 . ° C. The rate of heat loss from the hot water, and the surface temperature of the wall 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 concrete is constant. Properties The thermal conductivity of concrete is given to be k = 0.75 W/m °C. Analysis The shape factor for this configuration is given in Table 3-5 to be
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Unformatted text preview: 85 ° C L = 4 m D 32 ° C z z m 58 . 13 m) 03 . ( m) 075 . ( 8 ln ) m 4 ( 2 8 ln 2 = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ π π = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ π π = D z L S Then rate of heat loss from the hot water in 8 parallel pipes becomes W 4318 = ° − ° = − = C ) 32 85 )( C W/m. 75 . )( m 58 . 13 ( 8 ) ( 8 2 1 T T Sk Q & The surface temperature of the wall can be determined from C 37.6 ° = ° + ° = + = ⎯→ ⎯ − = = = ∞ ∞ ) m 64 )( C . W/m 12 ( W 4318 C 32 ) ( sides) both (from m 64 ) m 8 )( m 4 ( 2 2 2 2 s s s s s hA Q T T T T hA Q A & & 3-93...
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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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