(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A cavity block wall of area 10m^{2}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-'.

2. Relevant equations

H = kA[itex]\frac{ΔT}{L}[/itex]

H = [itex]\frac{A(ΔT)}{\sum\frac{l}{k}}[/itex]

3. 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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# Homework Help: Heat transfer in Cavity wall

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