Thermodynamics HW Solutions 282

# Thermodynamics HW Solutions 282 - Chapter 3 Steady Heat...

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Chapter 3 Steady Heat Conduction 3-171 Heat transfer through a window is considered. The percent error involved in the calculation of heat gain through the window assuming the window consist of glass only is to be determined. Assumptions 1 Heat transfer is steady. 2 Heat transfer is one-dimensional. 3 Thermal conductivities are constant. 4 Radiation is accounted for in heat transfer coefficients. Properties The thermal conductivities are given to be 0.7 W/m °C for glass and 0.12 W/m °C for pine wood. Analysis The surface areas of the glass and the wood and the individual thermal resistances are 2 wood 2 glass m 45 . 0 m) 2 ( m) 5 . 1 ( 15 . 0 m 55 . 2 m) 2 ( m) 5 . 1 ( 85 . 0 = = = = A A R i R glass T 1 T 2 R o R i R wood T 1 T 2 R o C/W 41433 . 1 17094 . 0 92593 . 0 31746 . 0 C/W 08787 . 0 03017 . 0 00168 . 0 05602 . 0 C/W 17094 . 0 ) m 45 . 0 ( C) . W/m 13 ( 1 1 C/W 03017 . 0 ) m 55 . 2 ( C) . W/m 13 ( 1 1 C/W 92593 . 0 ) m
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