Respuesta :
Answer:
Heat flow through walls in 10 hours is
[tex]Q = 6.1 \times 10^6 J[/tex]
Explanation:
Thermal conductivity of all the materials is as follows
1). Concrete = 0.8
2). Brick = 0.6
3). Fibreglass = 0.04
4). Corkboard = 0.04
Area of the wall is given as
[tex]A = (8 \times 4) = 32 m^2[/tex]
now the thermal resistance due to each wall is given as
[tex]R_1 = \frac{0.04}{0.6(32)} = 2.08 \times 10^{-3}[/tex]
[tex]R_2 = \frac{0.08}{0.8(32)} = 3.125 \times 10^{-3}[/tex]
[tex]R_3 = \frac{0.06}{0.04(32)} = 46.87 \times 10^{-3}[/tex]
[tex]R_2 = \frac{0.10}{0.04(32)} = 78.13 \times 10^{-3}[/tex]
Now total thermal resistance of all walls
[tex]R = R_1 + R_2 + R_3 + R_4[/tex]
[tex]R = (2.08 + 3.125 + 46.87 + 78.13) \times 10^{-3}[/tex]
[tex]R = 0.130[/tex]
now rate of heat transfer per second is given as
[tex]\frac{dQ}{dt} = \frac{T_1 - T_2}{R}[/tex]
[tex]Q = \frac{40 - 18}{0.130}(10 \times 3600)[/tex]
[tex]Q = 6.1 \times 10^6 J[/tex]
