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A window has a glass surface of 2907 cm2 and a thickness of 5.6 mm. Find the rate of energy transfer by conduction through this pane when the temperature of the inside surface of the glass is 71◦F and the outside temperature is 81 ◦F. Assume the thermal conductivity of window glass is 0.8 J/s · m · ◦ C . Answer in units of kW

Part BFind the rate of energy transfer for the same inside temperature and an outside temperature of 0◦F.

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Answer:

2.30714 W

-16.38071 W

Explanation:

k = Heat conduction coefficient = 0.8 W/(m·°C)

A = Area = 2907 cm²

l = Thickness = 5.6 mm

[tex]T_2[/tex] = Outside temperature

[tex]T_1[/tex] = Inside temperature

Rate of heat transfer is given by

[tex]Q=\frac{kA(T_2-T_1)}{l}\\\Rightarrow Q=\frac{0.8\times 2907\times 10^{-6}\times (81-71)\times \frac{5}{9}}{5.6\times 10^{-3}}\\\Rightarrow Q=2.30714\ W[/tex]

The rate of energy transfer is 2.30714 W

[tex]Q=\frac{kA(T_2-T_1)}{l}\\\Rightarrow Q=\frac{0.8\times 2907\times 10^{-6}\times (0-71)\times \frac{5}{9}}{5.6\times 10^{-3}}\\\Rightarrow Q=-16.38071\ W[/tex]

The rate of energy transfer is -16.38071 W

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