Question

A masonary wall $(k=0.75W/m-K)$ transfers $80\%$ of the heat loss through another wall $(k=0.25W/m-K,x=100mm).$ If the temperature difference across both the walls is same, the thickness of masonary wall would be

• A. 300 mm
• B. 375 mm
• C. 240 mm
• D. 150 mm

Answer 1

The correct option is B 375 mm

$\text{Heat loss through masonary wall}=80\%\times \text{heat loss through another wall}$

$\frac{k_1(T_1-T_2)}{x}=\frac{0.8\times k_2(T_1-T_2)}{100}$

$(T_1-T_2=\text{constant for both case)}$

$\frac{0.75}{x}=\frac{0.8\times 0.25}{100}$

$\Rightarrow x=375mm$