Thermopane window is constructed, using two layers of glass 4.0 mm thick, separated by an air space of 5.0 mm.

if the temperature difference is 20° c from the inside of the house to the outside air, what is the rate of heat flow through this window?

(thermal conductivity for glass is 0.84 j/s⋅m⋅°c and for air 0.023 4 j/s⋅m⋅°c.)
a. 7 700 wb. 1 900 wc. 547 wd. 180 w

To solve this problem it is necessary to apply the concepts related to rate of thermal conduction

The letter Q represents the amount of heat transferred in a time t, k is the thermal conductivity constant for the material, A is the cross sectional area of the material transferring heat, , T is the difference in temperature between one side of the material and the other, and d is the thickness of the material.

The change made between glass and air would be determined by:

There are two layers of Glass and one layer of Air so the total temperature would be given as,

Finally the rate of heat flow through this windows is given as,

Therefore the correct answer is D. 180W.

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