Question

A masonry wall having thermal conductivity of 0.75 W/m.K is subjected to the same temperature difference across it, as is the case for a composite wall having a thermal conductivity of 0.25 W/m.K and thickness of 100 mm. If the heat transfer rate through the masonry wall is 80% of the other one, then its thickness (correct to 1 decimal place) is ___________________ cm.

Answer 1

Answer:Given data,

Masonry wall

k1 = 0.75 W/mK,

Q1 = heat transfer rate through masonry wall = 0.8Q2

t1= ?

composite wall

k2 = 0.25 W/mK,

Q2 = heat transfer rate through composite wall

t2 = 100 mm

∴Q1 = 0.8 Q2

-k1×​A1(dT/dX)1=-0.8×k2×A1(dT/dX)2

0.75/t1=0.8*o.25/100

        t1= 375 mm