A picture window has dimensions of 1.40 meters x 2.50 meters and is made of glas

Question

A picture window has dimensions of 1.40 meters x 2.50 meters and is made of glass 5.30 millimeters thick. On a winter day, the outside temperature is -15.0 degrees Celcius, while the inside temperature is a comfortable 21.0 degrees Celcius.

Part A:

At what rate is heat being lost through the window by conduction? (Express your answer using three significant figures)

Part B:

At what rate would heat be lost through the window if you covered it with a 0.750 millimeter-thick layer of paper (thermal conductivity 0.05 Watts/Meters x Kelvin)?

Explanation / Answer

A) Heat transfer rate Q = kA (dT / dx) Q = 0.8*(1.4*2.5)*(21 - (-15)) / 0.0053 Q = 19018.868 W B) Total thermal resistance = 0.0053 / (0.8*(1.4*2.5)) + 0.00075 / (0.05*(1.4*2.5)) = 0.006178 Q = (21 - (-15)) / 0.006178 Q = 5826.5896 W

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