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A thermopane window consists of two pieces of glass each 0.1" thick separated by a layer...

A thermopane window consists of two pieces of glass each 0.1" thick separated by a layer of dry,
stagnant air .4" thick.
• Find the resistance of a 4 ft × 3 ft thermopane window.
• Suppose the window is made by fastening an aluminum border .1" thick all around the edge.
Find the total resistance for this configuration.
• As an alternative to the aluminum, we might use a border of .75" thick white pine. Find the total
resistance for this configuration. (For white pine, "across the grain", k = .087 Btu/hr ft °F).
• Calculate the heat loss for the two windows and compare with that for a single pane of .1" glass.

Solutions

Expert Solution

Thermopane
Glass Thickness 0.1 0.00254 m
Air 0.4 0.01016 m
L 4 1.2192 m
B 3 0.9144 m
kg 0.869 W/mK
ka 0.026 W/mK
R1 0.002622
R2 0.350517
R3 0.002622
Total Resistance 0.355761 K/W
Aluminium Border
Glass Thickness 0.1 0.00254 m
Air 0.4 0.01016 m
L 4 1.21412 m
B 3 0.90932 m
kg 0.869 W/mK
ka 0.026 W/mK
kal 0.022
R1 0.002647
R2 0.350517
R3 0.002647
R4 0.103562 0.100914
Total Resistance 0.456726 K/W
White Pine Border
Glass Thickness 0.1 0.00254 m
Air 0.4 0.01016 m
L 4 1.20015 m
B 3 0.89535 m
kg 0.869 W/mK
ka 0.026 W/mK
kp 1.5047 W/mk
R1 0.00272
R2 0.350517
R3 0.00272
R4 0.001514 -0.00121
Total Resistance 0.358677 K/W
Single Pane
Glass Thickness 0.1 0.00254 m
Air 0.4 0.01016 m
L 4 1.2192 m
B 3 0.9144 m
kg 0.869
ka 0.026
R1 0.002622
R2 0.350517
R3
Total Resistance 0.353139 K/W
Temperature Diff 5 K
Single Pane Heat Loss 15.78467 W/m
Double Pane Heat Loss 15.66835 W/m

Amanda K answered 3 years ago
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