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Darth Frodo
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Homework Statement
A cavity block wall of area 10m2 constructed of 100 mm concrete, 50 mm air gap, 50 mm of polystyrene and a second 100 mm wall of concrete. The wall contains three windows with dimensions of 0.5 m x 0.7 m with glass 4 mm thick. The outside temperature is 5 °c and the inside temperature is 20°C.
Calculate
(A) the flow of heat through the glass, and
(B) the total heat flow through the wall.
Average thermal conductivities are
Concrete 0.6 W m·' K-'.
Polystyrene 0.03 W m-' K-'.
Air 0.024 Wm-' K-'.
Glass 0.8 W m-' K-'.
Homework Equations
H = kA[itex]\frac{ΔT}{L}[/itex]
H = [itex]\frac{A(ΔT)}{\sum\frac{l}{k}}[/itex]
The Attempt at a Solution
(A) H = (0.8)(0.35)([itex]\frac{15}{0.004}[/itex])
H = 1050 J/K
Total Heat through Glass = 3150(B): Total heat = Heat though Cavity wall + Heat though windows + Heat through the concrete surrounding the windows
[itex]\frac{10(15)}{\frac{0.1}{0.6}+ \frac{0.05}{0.024}+ \frac{0.05}{0.03}}[/itex] + 3150 + [itex]\frac{(8.95)(15)(0.6)}{0.1}[/itex]
total = 3993.8 J/K
Is this correct?
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