(a) If a single pane glass window on a house has an area of 0.5 m 2 and is 3mm t
ID: 879261 • Letter: #
Question
(a) If a single pane glass window on a house has an area of 0.5 m2 and is 3mm thick, what is rate of heat loss through this window on a cold winter day when the inside surface of the glass is 15°C and the outside surface is 5°C? Assume the glass has k=2.0 W/m-K. (b) How much can the heat loss be reduced if the window is constructed to be double-pane (2 mm per pane) with a 5mm Argon filled spaced between the panes (assume the same temperature difference and a value of k=0.016W/m-K for Argon).
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For A I solved like this:
Q (Heat transfer) = k (conductivity) ×area/thickness×(d)T
(a) Q = 2W/mK×.5m²/.003m×10K = 3.3kW
(k for window glass is usually given as 1W/mC)
I can't get B. Will Rate!!
Explanation / Answer
(b)
area = 0.5 m2
thickness = 2 mm per pane (double pane)
space between the panes = 5 mm
k = 0.016 W/m-K (for argon)
Q = kA dT/dx
1 / Q = (1/Q1) + (1/Q2) + (1/Q3)
= 2 / (2 x 0.5 x 10/0.002) + 1 / (0.016 x 0.5 x 10/0.005)
= 0.0004 + 0.0625
= 0.0629
Q = 15.89 W
= 0.016 kW
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