The brick wall (of thermal conductivity 1.12 W/m · ◦ C) of a building has dimensions of 2.8 m by 5 m and is 8 cm thick. How much heat flows through the wall in a 16.7 h period when the average inside and outside temperatures are, respectively, 12◦C and 3◦C? Answer in units of

Explanation:

If H be the heat flowing in time t through an area of A having thickness d

H = k A x ( θ₂ - θ₁ ) t / d  , k is thermal conductivity , ( θ₂ - θ₁ ) is temperature difference of walls

putting the given values

= (1.12 x 2.8x 5 x 9 x 16.7 x 60 x 60) / .08

= 1.06 x 10⁸ J .

at right angles to each other