(a) Calculate the rate of heat conduction (in W) through a double-paned window t

Question

(a) Calculate the rate of heat conduction (in W) through a double-paned window that has a 2.50 m2 area and is made of two panes of 0.700 cm thick glass separated by a 1.00 cm air gap. The inside surface temperature is 21.0°C, while that on the outside is 16.0°C. (Hint: There are identical temperature drops across the two glass panes. First find these and then the temperature drop across the air gap. This problem ignores the increased heat transfer in the air gap due to convection.)

(b) Calculate the rate of heat conduction (in W) through a 1.40 cm-thick window of the same area and with the same temperatures.

Compare your answer with that for part (a).

Explanation / Answer

The rate of heat conductionis Q/t={kA(T2-T1)}/d

K is coefficient of thermal conductivity of glass=0.8

Area of the glass plate is 2.5m2

thickness of the plate is (0.7+1+0.7)cm=2.4×10-2m2

tis temperature difference between the two surfaces

Q/t={0.8×2.5×37}/2.4×10-2 =74/2.4×102=3083.3W

(b)Now the thickness of the glass plate is 1.4cm

(b)Q/t={0.8×2.5×37}/3.8×10-2=74/3.8×102=1947.36W

As the thickness of the glass increases the rate of conduction has been reduced

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