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.

L_1 = 375 mm

Explanation:

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

Where 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

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

L_1 = 375 mm

c. magnitude and direction

0.93xc=0.93x3x10^8m/s

2.54cm is 1 inch

360seconds i 1 hr