Question

Homes are often insulated with fiberglass insulation in their walls and ceiling. The thermal conductivity of fiberglass is 0.040 W/(m?K).Suppose that the total surface area of the walls and roof of a windowless house is 470m2 and that the thickness of the insulation is 17cm .At what rate does heat leave the house on a day when the outside temperature is 30 ?C colder than the inside temperature?

Answer 1

Answer:

2.866 x 10^8 J

Explanation:

Thermal conductivity, K = 0.040 W/m^2 k

Area of the wall, A = 470 m^2

Thickness, d = 17 cm = 0.17 m

difference in temperature, ΔT = 30° C

The rate of heat flow is H.

Time, t = 1 day = 1 x 24 x 60 x 60 second = 86400 second

By use of formula of heat flow

$H=\frac{K A \Delta T}{d}t$

$H=\frac{0.040 \times 470 \times 30}{0.17}\times 86400$

H = 2.866 x 10^8 J