Problem #$4$

A section of a composite wall with the dimensions shown below has uniform temperatures of $200C$ and $50C$ over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: $k_A=70\frac{W}{m-K},k_B=60\frac{W}{m-K},k_c=40\frac{W}{m-K}$ and $k_D=20\frac{W}{m-K},$ determine

$($a$)$ The rate of heat transfer through this section of the wall and the temperatures at the interfaces.

$($b$)$ Repeat problem $($a$)$ including a contact resistance of $0\mathrm{.}1\frac{K}{W}$ at each of the interfaces.

Comment on how the rate of heat transfer through the wall section will be affected with the inclusion of the contact resistance. $[$Apply the thermal circuit for the composite wall$]$