The temperature drop through a two layer furnace wall is `600^(@)C`. Each layer is of equal area of cross section. Which of the following actions will result in lowering the temperature `theta` of the interface ?

Options

A. By increasing the thermal conductivity of inner layer.
B. By increasig the thermal conductivity of outer layer
C. By increasing thickness of outer layer
D. By decreasing thickness of inner layer

Answer

A, B, D

Explanation

In steady state, `(K_(1) A (1000 - theta))/(L_(1))`
`= (K_(2) A (theta - 400))/(L_(2))`
`1000 (K_(1))/(L_(1)) - (K_(1))/(L_(1)) theta = (K_(2) theta)/(L_(2)) - 400 (K_(2))/(L_(2))`
`theta = (1000(K_(1))/(L_(1)) + 400 (K_(2))/(L_(2)))/((K_(1))/(L_(1)) + (K_(2))/(L_(2)))`