Question

What is the thickness required of a masonry wall having thermal conductivity 0.75 W/mK if the heat rate is to be 80% of the heat rate through a composite structural wall having a thermal conductivity of 0.25 W/m K and a thickness of 100 mm? Both walls are subjected to the same surface temperature difference.

Answer 1

Answer:

L_1 = 375 mm

Explanation:

according to the fourier's  law, the relation for heat rate is given as

$q^{'} = k*\frac {\Delta T}{L}$

Where $\Delta T$ is difference in temperature of surface and it is given in the question temperature difference is same for both given wall

so we have now

$L_1 = L_2*\frac {k_1}{k_2}$

MASONARY WALL HEAT RATE q1 is 80% OF STRUCTURAL WALL HEAT RATE q2

$L_1 = 0.80(100*\frac {0.75}{0.25})$

L_1 = 375 mm